Adjust vendor import of llvm-project main llvmorg-21-init-19288-gface93e724f4: add partial libc/ top-level directory.

17 files changed, 1297 insertions, 0 deletions

diff --git a/libc/shared/fp_bits.h b/libc/shared/fp_bits.h
new file mode 100644
index 000000000000..e6bb1e17b80c
--- /dev/null
+++ b/libc/shared/fp_bits.h
@@ -0,0 +1,23 @@
+//===-- Floating point number utils -----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_FP_BITS_H
+#define LLVM_LIBC_SHARED_FP_BITS_H
+
+#include "libc_common.h"
+#include "src/__support/FPUtil/FPBits.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using fputil::FPBits;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_FP_BITS_H
diff --git a/libc/shared/libc_common.h b/libc/shared/libc_common.h
new file mode 100644
index 000000000000..c4560bbb0276
--- /dev/null
+++ b/libc/shared/libc_common.h
@@ -0,0 +1,26 @@
+//===-- Common defines for sharing LLVM libc with LLVM projects -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_LIBC_COMMON_H
+#define LLVM_LIBC_SHARED_LIBC_COMMON_H
+
+// Use system errno.
+#ifdef LIBC_ERRNO_MODE
+#if LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM_INLINE
+#error                                                                         \
+    "LIBC_ERRNO_MODE was set to something different from LIBC_ERRNO_MODE_SYSTEM_INLINE."
+#endif // LIBC_ERRNO_MODE != LIBC_ERRNO_MODE_SYSTEM_INLINE
+#else
+#define LIBC_ERRNO_MODE LIBC_ERRNO_MODE_SYSTEM_INLINE
+#endif // LIBC_ERRNO_MODE
+
+#ifndef LIBC_NAMESPACE
+#define LIBC_NAMESPACE __llvm_libc
+#endif // LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SHARED_LIBC_COMMON_H
diff --git a/libc/shared/math.h b/libc/shared/math.h
new file mode 100644
index 000000000000..b2f1a03e0940
--- /dev/null
+++ b/libc/shared/math.h
@@ -0,0 +1,23 @@
+//===-- Floating point math functions ---------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_H
+#define LLVM_LIBC_SHARED_MATH_H
+
+#include "libc_common.h"
+
+#include "math/expf.h"
+#include "math/expf16.h"
+#include "math/frexpf.h"
+#include "math/frexpf128.h"
+#include "math/frexpf16.h"
+#include "math/ldexpf.h"
+#include "math/ldexpf128.h"
+#include "math/ldexpf16.h"
+
+#endif // LLVM_LIBC_SHARED_MATH_H
diff --git a/libc/shared/math/expf.h b/libc/shared/math/expf.h
new file mode 100644
index 000000000000..a4e8b0751bb4
--- /dev/null
+++ b/libc/shared/math/expf.h
@@ -0,0 +1,23 @@
+//===-- Shared expf function ------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_EXPF_H
+#define LLVM_LIBC_SHARED_MATH_EXPF_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/expf.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::expf;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_EXPF_H
diff --git a/libc/shared/math/expf16.h b/libc/shared/math/expf16.h
new file mode 100644
index 000000000000..a6a3e89e680d
--- /dev/null
+++ b/libc/shared/math/expf16.h
@@ -0,0 +1,29 @@
+//===-- Shared expf16 function ----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_EXPF16_H
+#define LLVM_LIBC_SHARED_MATH_EXPF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include "shared/libc_common.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/math/expf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::expf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_EXPF16_H
diff --git a/libc/shared/math/frexpf.h b/libc/shared/math/frexpf.h
new file mode 100644
index 000000000000..35f23a70eb25
--- /dev/null
+++ b/libc/shared/math/frexpf.h
@@ -0,0 +1,24 @@
+//===-- Shared frexpf function ------------------------------------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_FREXPF_H
+#define LLVM_LIBC_SHARED_MATH_FREXPF_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/frexpf.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::frexpf;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_FREXPF_H
diff --git a/libc/shared/math/frexpf128.h b/libc/shared/math/frexpf128.h
new file mode 100644
index 000000000000..6b922bd73129
--- /dev/null
+++ b/libc/shared/math/frexpf128.h
@@ -0,0 +1,29 @@
+//===-- Shared frexpf128 function -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_FREXPF128_H
+#define LLVM_LIBC_SHARED_MATH_FREXPF128_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/math/frexpf128.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::frexpf128;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_MATH_FREXPF128_H
diff --git a/libc/shared/math/frexpf16.h b/libc/shared/math/frexpf16.h
new file mode 100644
index 000000000000..24b2883a6f91
--- /dev/null
+++ b/libc/shared/math/frexpf16.h
@@ -0,0 +1,29 @@
+//===-- Shared frexpf16 function --------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_FREXPF16_H
+#define LLVM_LIBC_SHARED_MATH_FREXPF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include "shared/libc_common.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/math/frexpf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::frexpf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_FREXPF16_H
diff --git a/libc/shared/math/ldexpf.h b/libc/shared/math/ldexpf.h
new file mode 100644
index 000000000000..497933c47321
--- /dev/null
+++ b/libc/shared/math/ldexpf.h
@@ -0,0 +1,23 @@
+//===-- Shared ldexpf function ----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_LDEXPF_H
+#define LLVM_LIBC_SHARED_MATH_LDEXPF_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/ldexpf.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::ldexpf;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_LDEXPF_H
diff --git a/libc/shared/math/ldexpf128.h b/libc/shared/math/ldexpf128.h
new file mode 100644
index 000000000000..d4066beb809c
--- /dev/null
+++ b/libc/shared/math/ldexpf128.h
@@ -0,0 +1,29 @@
+//===-- Shared ldexpf128 function -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_LDEXPF128_H
+#define LLVM_LIBC_SHARED_MATH_LDEXPF128_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/math/ldexpf128.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::ldexpf128;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_MATH_LDEXPF128_H
diff --git a/libc/shared/math/ldexpf16.h b/libc/shared/math/ldexpf16.h
new file mode 100644
index 000000000000..4c98c4c78d46
--- /dev/null
+++ b/libc/shared/math/ldexpf16.h
@@ -0,0 +1,31 @@
+//===-- Shared ldexpf16 function --------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_LDEXPF16_H
+#define LLVM_LIBC_SHARED_MATH_LDEXPF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "shared/libc_common.h"
+#include "src/__support/math/ldexpf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace shared {
+
+using math::ldexpf16;
+
+} // namespace shared
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_LDEXPF16_H
diff --git a/libc/shared/rpc.h b/libc/shared/rpc.h
new file mode 100644
index 000000000000..7295efd4eee3
--- /dev/null
+++ b/libc/shared/rpc.h
@@ -0,0 +1,603 @@
+//===-- Shared memory RPC client / server interface -------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a remote procedure call mechanism to communicate between
+// heterogeneous devices that can share an address space atomically. We provide
+// a client and a server to facilitate the remote call. The client makes request
+// to the server using a shared communication channel. We use separate atomic
+// signals to indicate which side, the client or the server is in ownership of
+// the buffer.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_RPC_H
+#define LLVM_LIBC_SHARED_RPC_H
+
+#include "rpc_util.h"
+
+namespace rpc {
+
+/// Use scoped atomic variants if they are available for the target.
+#if !__has_builtin(__scoped_atomic_load_n)
+#define __scoped_atomic_load_n(src, ord, scp) __atomic_load_n(src, ord)
+#define __scoped_atomic_store_n(dst, src, ord, scp)                            \
+  __atomic_store_n(dst, src, ord)
+#define __scoped_atomic_fetch_or(src, val, ord, scp)                           \
+  __atomic_fetch_or(src, val, ord)
+#define __scoped_atomic_fetch_and(src, val, ord, scp)                          \
+  __atomic_fetch_and(src, val, ord)
+#endif
+#if !__has_builtin(__scoped_atomic_thread_fence)
+#define __scoped_atomic_thread_fence(ord, scp) __atomic_thread_fence(ord)
+#endif
+
+/// Generic codes that can be used whem implementing the server.
+enum Status {
+  RPC_SUCCESS = 0x0,
+  RPC_ERROR = 0x1000,
+  RPC_UNHANDLED_OPCODE = 0x1001,
+};
+
+/// A fixed size channel used to communicate between the RPC client and server.
+struct Buffer {
+  uint64_t data[8];
+};
+static_assert(sizeof(Buffer) == 64, "Buffer size mismatch");
+
+/// The information associated with a packet. This indicates which operations to
+/// perform and which threads are active in the slots.
+struct Header {
+  uint64_t mask;
+  uint32_t opcode;
+};
+
+/// The maximum number of parallel ports that the RPC interface can support.
+constexpr static uint64_t MAX_PORT_COUNT = 4096;
+
+/// A common process used to synchronize communication between a client and a
+/// server. The process contains a read-only inbox and a write-only outbox used
+/// for signaling ownership of the shared buffer between both sides. We assign
+/// ownership of the buffer to the client if the inbox and outbox bits match,
+/// otherwise it is owned by the server.
+///
+/// This process is designed to allow the client and the server to exchange data
+/// using a fixed size packet in a mostly arbitrary order using the 'send' and
+/// 'recv' operations. The following restrictions to this scheme apply:
+///   - The client will always start with a 'send' operation.
+///   - The server will always start with a 'recv' operation.
+///   - Every 'send' or 'recv' call is mirrored by the other process.
+template <bool Invert> struct Process {
+  RPC_ATTRS Process() = default;
+  RPC_ATTRS Process(const Process &) = delete;
+  RPC_ATTRS Process &operator=(const Process &) = delete;
+  RPC_ATTRS Process(Process &&) = default;
+  RPC_ATTRS Process &operator=(Process &&) = default;
+  RPC_ATTRS ~Process() = default;
+
+  const uint32_t port_count = 0;
+  const uint32_t *const inbox = nullptr;
+  uint32_t *const outbox = nullptr;
+  Header *const header = nullptr;
+  Buffer *const packet = nullptr;
+
+  static constexpr uint64_t NUM_BITS_IN_WORD = sizeof(uint32_t) * 8;
+  uint32_t lock[MAX_PORT_COUNT / NUM_BITS_IN_WORD] = {0};
+
+  RPC_ATTRS Process(uint32_t port_count, void *buffer)
+      : port_count(port_count), inbox(reinterpret_cast<uint32_t *>(
+                                    advance(buffer, inbox_offset(port_count)))),
+        outbox(reinterpret_cast<uint32_t *>(
+            advance(buffer, outbox_offset(port_count)))),
+        header(reinterpret_cast<Header *>(
+            advance(buffer, header_offset(port_count)))),
+        packet(reinterpret_cast<Buffer *>(
+            advance(buffer, buffer_offset(port_count)))) {}
+
+  /// Allocate a memory buffer sufficient to store the following equivalent
+  /// representation in memory.
+  ///
+  /// struct Equivalent {
+  ///   Atomic<uint32_t> primary[port_count];
+  ///   Atomic<uint32_t> secondary[port_count];
+  ///   Header header[port_count];
+  ///   Buffer packet[port_count][lane_size];
+  /// };
+  RPC_ATTRS static constexpr uint64_t allocation_size(uint32_t port_count,
+                                                      uint32_t lane_size) {
+    return buffer_offset(port_count) + buffer_bytes(port_count, lane_size);
+  }
+
+  /// Retrieve the inbox state from memory shared between processes.
+  RPC_ATTRS uint32_t load_inbox(uint64_t lane_mask, uint32_t index) const {
+    return rpc::broadcast_value(
+        lane_mask, __scoped_atomic_load_n(&inbox[index], __ATOMIC_RELAXED,
+                                          __MEMORY_SCOPE_SYSTEM));
+  }
+
+  /// Retrieve the outbox state from memory shared between processes.
+  RPC_ATTRS uint32_t load_outbox(uint64_t lane_mask, uint32_t index) const {
+    return rpc::broadcast_value(
+        lane_mask, __scoped_atomic_load_n(&outbox[index], __ATOMIC_RELAXED,
+                                          __MEMORY_SCOPE_SYSTEM));
+  }
+
+  /// Signal to the other process that this one is finished with the buffer.
+  /// Equivalent to loading outbox followed by store of the inverted value
+  /// The outbox is write only by this warp and tracking the value locally is
+  /// cheaper than calling load_outbox to get the value to store.
+  RPC_ATTRS uint32_t invert_outbox(uint32_t index, uint32_t current_outbox) {
+    uint32_t inverted_outbox = !current_outbox;
+    __scoped_atomic_thread_fence(__ATOMIC_RELEASE, __MEMORY_SCOPE_SYSTEM);
+    __scoped_atomic_store_n(&outbox[index], inverted_outbox, __ATOMIC_RELAXED,
+                            __MEMORY_SCOPE_SYSTEM);
+    return inverted_outbox;
+  }
+
+  // Given the current outbox and inbox values, wait until the inbox changes
+  // to indicate that this thread owns the buffer element.
+  RPC_ATTRS void wait_for_ownership(uint64_t lane_mask, uint32_t index,
+                                    uint32_t outbox, uint32_t in) {
+    while (buffer_unavailable(in, outbox)) {
+      sleep_briefly();
+      in = load_inbox(lane_mask, index);
+    }
+    __scoped_atomic_thread_fence(__ATOMIC_ACQUIRE, __MEMORY_SCOPE_SYSTEM);
+  }
+
+  /// The packet is a linearly allocated array of buffers used to communicate
+  /// with the other process. This function returns the appropriate slot in this
+  /// array such that the process can operate on an entire warp or wavefront.
+  RPC_ATTRS Buffer *get_packet(uint32_t index, uint32_t lane_size) {
+    return &packet[index * lane_size];
+  }
+
+  /// Determines if this process needs to wait for ownership of the buffer. We
+  /// invert the condition on one of the processes to indicate that if one
+  /// process owns the buffer then the other does not.
+  RPC_ATTRS static bool buffer_unavailable(uint32_t in, uint32_t out) {
+    bool cond = in != out;
+    return Invert ? !cond : cond;
+  }
+
+  /// Attempt to claim the lock at index. Return true on lock taken.
+  /// lane_mask is a bitmap of the threads in the warp that would hold the
+  /// single lock on success, e.g. the result of rpc::get_lane_mask()
+  /// The lock is held when the n-th bit of the lock bitfield is set.
+  RPC_ATTRS bool try_lock(uint64_t lane_mask, uint32_t index) {
+    // On amdgpu, test and set to the nth lock bit and a sync_lane would suffice
+    // On volta, need to handle differences between the threads running and
+    // the threads that were detected in the previous call to get_lane_mask()
+    //
+    // All threads in lane_mask try to claim the lock. At most one can succeed.
+    // There may be threads active which are not in lane mask which must not
+    // succeed in taking the lock, as otherwise it will leak. This is handled
+    // by making threads which are not in lane_mask or with 0, a no-op.
+    uint32_t id = rpc::get_lane_id();
+    bool id_in_lane_mask = lane_mask & (1ul << id);
+
+    // All threads in the warp call fetch_or. Possibly at the same time.
+    bool before = set_nth(lock, index, id_in_lane_mask);
+    uint64_t packed = rpc::ballot(lane_mask, before);
+
+    // If every bit set in lane_mask is also set in packed, every single thread
+    // in the warp failed to get the lock. Ballot returns unset for threads not
+    // in the lane mask.
+    //
+    // Cases, per thread:
+    // mask==0 -> unspecified before, discarded by ballot -> 0
+    // mask==1 and before==0 (success), set zero by ballot -> 0
+    // mask==1 and before==1 (failure), set one by ballot -> 1
+    //
+    // mask != packed implies at least one of the threads got the lock
+    // atomic semantics of fetch_or mean at most one of the threads for the lock
+
+    // If holding the lock then the caller can load values knowing said loads
+    // won't move past the lock. No such guarantee is needed if the lock acquire
+    // failed. This conditional branch is expected to fold in the caller after
+    // inlining the current function.
+    bool holding_lock = lane_mask != packed;
+    if (holding_lock)
+      __scoped_atomic_thread_fence(__ATOMIC_ACQUIRE, __MEMORY_SCOPE_DEVICE);
+    return holding_lock;
+  }
+
+  /// Unlock the lock at index. We need a lane sync to keep this function
+  /// convergent, otherwise the compiler will sink the store and deadlock.
+  RPC_ATTRS void unlock(uint64_t lane_mask, uint32_t index) {
+    // Do not move any writes past the unlock.
+    __scoped_atomic_thread_fence(__ATOMIC_RELEASE, __MEMORY_SCOPE_DEVICE);
+
+    // Use exactly one thread to clear the nth bit in the lock array Must
+    // restrict to a single thread to avoid one thread dropping the lock, then
+    // an unrelated warp claiming the lock, then a second thread in this warp
+    // dropping the lock again.
+    clear_nth(lock, index, rpc::is_first_lane(lane_mask));
+    rpc::sync_lane(lane_mask);
+  }
+
+  /// Number of bytes to allocate for an inbox or outbox.
+  RPC_ATTRS static constexpr uint64_t mailbox_bytes(uint32_t port_count) {
+    return port_count * sizeof(uint32_t);
+  }
+
+  /// Number of bytes to allocate for the buffer containing the packets.
+  RPC_ATTRS static constexpr uint64_t buffer_bytes(uint32_t port_count,
+                                                   uint32_t lane_size) {
+    return port_count * lane_size * sizeof(Buffer);
+  }
+
+  /// Offset of the inbox in memory. This is the same as the outbox if inverted.
+  RPC_ATTRS static constexpr uint64_t inbox_offset(uint32_t port_count) {
+    return Invert ? mailbox_bytes(port_count) : 0;
+  }
+
+  /// Offset of the outbox in memory. This is the same as the inbox if inverted.
+  RPC_ATTRS static constexpr uint64_t outbox_offset(uint32_t port_count) {
+    return Invert ? 0 : mailbox_bytes(port_count);
+  }
+
+  /// Offset of the buffer containing the packets after the inbox and outbox.
+  RPC_ATTRS static constexpr uint64_t header_offset(uint32_t port_count) {
+    return align_up(2 * mailbox_bytes(port_count), alignof(Header));
+  }
+
+  /// Offset of the buffer containing the packets after the inbox and outbox.
+  RPC_ATTRS static constexpr uint64_t buffer_offset(uint32_t port_count) {
+    return align_up(header_offset(port_count) + port_count * sizeof(Header),
+                    alignof(Buffer));
+  }
+
+  /// Conditionally set the n-th bit in the atomic bitfield.
+  RPC_ATTRS static constexpr uint32_t set_nth(uint32_t *bits, uint32_t index,
+                                              bool cond) {
+    uint32_t slot = index / NUM_BITS_IN_WORD;
+    uint32_t bit = index % NUM_BITS_IN_WORD;
+    return __scoped_atomic_fetch_or(&bits[slot],
+                                    static_cast<uint32_t>(cond) << bit,
+                                    __ATOMIC_RELAXED, __MEMORY_SCOPE_DEVICE) &
+           (1u << bit);
+  }
+
+  /// Conditionally clear the n-th bit in the atomic bitfield.
+  RPC_ATTRS static constexpr uint32_t clear_nth(uint32_t *bits, uint32_t index,
+                                                bool cond) {
+    uint32_t slot = index / NUM_BITS_IN_WORD;
+    uint32_t bit = index % NUM_BITS_IN_WORD;
+    return __scoped_atomic_fetch_and(&bits[slot],
+                                     ~0u ^ (static_cast<uint32_t>(cond) << bit),
+                                     __ATOMIC_RELAXED, __MEMORY_SCOPE_DEVICE) &
+           (1u << bit);
+  }
+};
+
+/// Invokes a function across every active buffer across the total lane size.
+template <typename F>
+RPC_ATTRS static void invoke_rpc(F &&fn, uint32_t lane_size, uint64_t lane_mask,
+                                 Buffer *slot) {
+  if constexpr (is_process_gpu()) {
+    fn(&slot[rpc::get_lane_id()], rpc::get_lane_id());
+  } else {
+    for (uint32_t i = 0; i < lane_size; i += rpc::get_num_lanes())
+      if (lane_mask & (1ul << i))
+        fn(&slot[i], i);
+  }
+}
+
+/// The port provides the interface to communicate between the multiple
+/// processes. A port is conceptually an index into the memory provided by the
+/// underlying process that is guarded by a lock bit.
+template <bool T> struct Port {
+  RPC_ATTRS Port(Process<T> &process, uint64_t lane_mask, uint32_t lane_size,
+                 uint32_t index, uint32_t out)
+      : process(process), lane_mask(lane_mask), lane_size(lane_size),
+        index(index), out(out), receive(false), owns_buffer(true) {}
+  RPC_ATTRS ~Port() = default;
+
+private:
+  RPC_ATTRS Port(const Port &) = delete;
+  RPC_ATTRS Port &operator=(const Port &) = delete;
+  RPC_ATTRS Port(Port &&) = default;
+  RPC_ATTRS Port &operator=(Port &&) = default;
+
+  friend struct Client;
+  friend struct Server;
+  friend class rpc::optional<Port<T>>;
+
+public:
+  template <typename U> RPC_ATTRS void recv(U use);
+  template <typename F> RPC_ATTRS void send(F fill);
+  template <typename F, typename U> RPC_ATTRS void send_and_recv(F fill, U use);
+  template <typename W> RPC_ATTRS void recv_and_send(W work);
+  RPC_ATTRS void send_n(const void *const *src, uint64_t *size);
+  RPC_ATTRS void send_n(const void *src, uint64_t size);
+  template <typename A>
+  RPC_ATTRS void recv_n(void **dst, uint64_t *size, A &&alloc);
+
+  RPC_ATTRS uint32_t get_opcode() const { return process.header[index].opcode; }
+
+  RPC_ATTRS uint32_t get_index() const { return index; }
+
+  RPC_ATTRS void close() {
+    // Wait for all lanes to finish using the port.
+    rpc::sync_lane(lane_mask);
+
+    // The server is passive, if it own the buffer when it closes we need to
+    // give ownership back to the client.
+    if (owns_buffer && T)
+      out = process.invert_outbox(index, out);
+    process.unlock(lane_mask, index);
+  }
+
+private:
+  Process<T> &process;
+  uint64_t lane_mask;
+  uint32_t lane_size;
+  uint32_t index;
+  uint32_t out;
+  bool receive;
+  bool owns_buffer;
+};
+
+/// The RPC client used to make requests to the server.
+struct Client {
+  RPC_ATTRS Client() = default;
+  RPC_ATTRS Client(const Client &) = delete;
+  RPC_ATTRS Client &operator=(const Client &) = delete;
+  RPC_ATTRS ~Client() = default;
+
+  RPC_ATTRS Client(uint32_t port_count, void *buffer)
+      : process(port_count, buffer) {}
+
+  using Port = rpc::Port<false>;
+  template <uint32_t opcode> RPC_ATTRS Port open();
+
+private:
+  Process<false> process;
+};
+
+/// The RPC server used to respond to the client.
+struct Server {
+  RPC_ATTRS Server() = default;
+  RPC_ATTRS Server(const Server &) = delete;
+  RPC_ATTRS Server &operator=(const Server &) = delete;
+  RPC_ATTRS ~Server() = default;
+
+  RPC_ATTRS Server(uint32_t port_count, void *buffer)
+      : process(port_count, buffer) {}
+
+  using Port = rpc::Port<true>;
+  RPC_ATTRS rpc::optional<Port> try_open(uint32_t lane_size,
+                                         uint32_t start = 0);
+  RPC_ATTRS Port open(uint32_t lane_size);
+
+  RPC_ATTRS static constexpr uint64_t allocation_size(uint32_t lane_size,
+                                                      uint32_t port_count) {
+    return Process<true>::allocation_size(port_count, lane_size);
+  }
+
+private:
+  Process<true> process;
+};
+
+/// Applies \p fill to the shared buffer and initiates a send operation.
+template <bool T> template <typename F> RPC_ATTRS void Port<T>::send(F fill) {
+  uint32_t in = owns_buffer ? out ^ T : process.load_inbox(lane_mask, index);
+
+  // We need to wait until we own the buffer before sending.
+  process.wait_for_ownership(lane_mask, index, out, in);
+
+  // Apply the \p fill function to initialize the buffer and release the memory.
+  invoke_rpc(fill, lane_size, process.header[index].mask,
+             process.get_packet(index, lane_size));
+  out = process.invert_outbox(index, out);
+  owns_buffer = false;
+  receive = false;
+}
+
+/// Applies \p use to the shared buffer and acknowledges the send.
+template <bool T> template <typename U> RPC_ATTRS void Port<T>::recv(U use) {
+  // We only exchange ownership of the buffer during a receive if we are waiting
+  // for a previous receive to finish.
+  if (receive) {
+    out = process.invert_outbox(index, out);
+    owns_buffer = false;
+  }
+
+  uint32_t in = owns_buffer ? out ^ T : process.load_inbox(lane_mask, index);
+
+  // We need to wait until we own the buffer before receiving.
+  process.wait_for_ownership(lane_mask, index, out, in);
+
+  // Apply the \p use function to read the memory out of the buffer.
+  invoke_rpc(use, lane_size, process.header[index].mask,
+             process.get_packet(index, lane_size));
+  receive = true;
+  owns_buffer = true;
+}
+
+/// Combines a send and receive into a single function.
+template <bool T>
+template <typename F, typename U>
+RPC_ATTRS void Port<T>::send_and_recv(F fill, U use) {
+  send(fill);
+  recv(use);
+}
+
+/// Combines a receive and send operation into a single function. The \p work
+/// function modifies the buffer in-place and the send is only used to initiate
+/// the copy back.
+template <bool T>
+template <typename W>
+RPC_ATTRS void Port<T>::recv_and_send(W work) {
+  recv(work);
+  send([](Buffer *, uint32_t) { /* no-op */ });
+}
+
+/// Helper routine to simplify the interface when sending from the GPU using
+/// thread private pointers to the underlying value.
+template <bool T>
+RPC_ATTRS void Port<T>::send_n(const void *src, uint64_t size) {
+  const void **src_ptr = &src;
+  uint64_t *size_ptr = &size;
+  send_n(src_ptr, size_ptr);
+}
+
+/// Sends an arbitrarily sized data buffer \p src across the shared channel in
+/// multiples of the packet length.
+template <bool T>
+RPC_ATTRS void Port<T>::send_n(const void *const *src, uint64_t *size) {
+  uint64_t num_sends = 0;
+  send([&](Buffer *buffer, uint32_t id) {
+    reinterpret_cast<uint64_t *>(buffer->data)[0] = lane_value(size, id);
+    num_sends = is_process_gpu() ? lane_value(size, id)
+                                 : rpc::max(lane_value(size, id), num_sends);
+    uint64_t len =
+        lane_value(size, id) > sizeof(Buffer::data) - sizeof(uint64_t)
+            ? sizeof(Buffer::data) - sizeof(uint64_t)
+            : lane_value(size, id);
+    rpc_memcpy(&buffer->data[1], lane_value(src, id), len);
+  });
+  uint64_t idx = sizeof(Buffer::data) - sizeof(uint64_t);
+  uint64_t mask = process.header[index].mask;
+  while (rpc::ballot(mask, idx < num_sends)) {
+    send([=](Buffer *buffer, uint32_t id) {
+      uint64_t len = lane_value(size, id) - idx > sizeof(Buffer::data)
+                         ? sizeof(Buffer::data)
+                         : lane_value(size, id) - idx;
+      if (idx < lane_value(size, id))
+        rpc_memcpy(buffer->data, advance(lane_value(src, id), idx), len);
+    });
+    idx += sizeof(Buffer::data);
+  }
+}
+
+/// Receives an arbitrarily sized data buffer across the shared channel in
+/// multiples of the packet length. The \p alloc function is called with the
+/// size of the data so that we can initialize the size of the \p dst buffer.
+template <bool T>
+template <typename A>
+RPC_ATTRS void Port<T>::recv_n(void **dst, uint64_t *size, A &&alloc) {
+  uint64_t num_recvs = 0;
+  recv([&](Buffer *buffer, uint32_t id) {
+    lane_value(size, id) = reinterpret_cast<uint64_t *>(buffer->data)[0];
+    lane_value(dst, id) =
+        reinterpret_cast<uint8_t *>(alloc(lane_value(size, id)));
+    num_recvs = is_process_gpu() ? lane_value(size, id)
+                                 : rpc::max(lane_value(size, id), num_recvs);
+    uint64_t len =
+        lane_value(size, id) > sizeof(Buffer::data) - sizeof(uint64_t)
+            ? sizeof(Buffer::data) - sizeof(uint64_t)
+            : lane_value(size, id);
+    rpc_memcpy(lane_value(dst, id), &buffer->data[1], len);
+  });
+  uint64_t idx = sizeof(Buffer::data) - sizeof(uint64_t);
+  uint64_t mask = process.header[index].mask;
+  while (rpc::ballot(mask, idx < num_recvs)) {
+    recv([=](Buffer *buffer, uint32_t id) {
+      uint64_t len = lane_value(size, id) - idx > sizeof(Buffer::data)
+                         ? sizeof(Buffer::data)
+                         : lane_value(size, id) - idx;
+      if (idx < lane_value(size, id))
+        rpc_memcpy(advance(lane_value(dst, id), idx), buffer->data, len);
+    });
+    idx += sizeof(Buffer::data);
+  }
+}
+
+/// Continually attempts to open a port to use as the client. The client can
+/// only open a port if we find an index that is in a valid sending state. That
+/// is, there are send operations pending that haven't been serviced on this
+/// port. Each port instance uses an associated \p opcode to tell the server
+/// what to do. The Client interface provides the appropriate lane size to the
+/// port using the platform's returned value.
+template <uint32_t opcode> RPC_ATTRS Client::Port Client::open() {
+  // Repeatedly perform a naive linear scan for a port that can be opened to
+  // send data.
+  for (uint32_t index = 0;; ++index) {
+    // Start from the beginning if we run out of ports to check.
+    if (index >= process.port_count)
+      index = 0;
+
+    // Attempt to acquire the lock on this index.
+    uint64_t lane_mask = rpc::get_lane_mask();
+    if (!process.try_lock(lane_mask, index))
+      continue;
+
+    uint32_t in = process.load_inbox(lane_mask, index);
+    uint32_t out = process.load_outbox(lane_mask, index);
+
+    // Once we acquire the index we need to check if we are in a valid sending
+    // state.
+    if (process.buffer_unavailable(in, out)) {
+      process.unlock(lane_mask, index);
+      continue;
+    }
+
+    if (rpc::is_first_lane(lane_mask)) {
+      process.header[index].opcode = opcode;
+      process.header[index].mask = lane_mask;
+    }
+    rpc::sync_lane(lane_mask);
+    return Port(process, lane_mask, rpc::get_num_lanes(), index, out);
+  }
+}
+
+/// Attempts to open a port to use as the server. The server can only open a
+/// port if it has a pending receive operation
+RPC_ATTRS rpc::optional<typename Server::Port>
+Server::try_open(uint32_t lane_size, uint32_t start) {
+  // Perform a naive linear scan for a port that has a pending request.
+  for (uint32_t index = start; index < process.port_count; ++index) {
+    uint64_t lane_mask = rpc::get_lane_mask();
+    uint32_t in = process.load_inbox(lane_mask, index);
+    uint32_t out = process.load_outbox(lane_mask, index);
+
+    // The server is passive, if there is no work pending don't bother
+    // opening a port.
+    if (process.buffer_unavailable(in, out))
+      continue;
+
+    // Attempt to acquire the lock on this index.
+    if (!process.try_lock(lane_mask, index))
+      continue;
+
+    in = process.load_inbox(lane_mask, index);
+    out = process.load_outbox(lane_mask, index);
+
+    if (process.buffer_unavailable(in, out)) {
+      process.unlock(lane_mask, index);
+      continue;
+    }
+
+    return Port(process, lane_mask, lane_size, index, out);
+  }
+  return rpc::nullopt;
+}
+
+RPC_ATTRS Server::Port Server::open(uint32_t lane_size) {
+  for (;;) {
+    if (rpc::optional<Server::Port> p = try_open(lane_size))
+      return rpc::move(p.value());
+    sleep_briefly();
+  }
+}
+
+#undef RPC_ATTRS
+#if !__has_builtin(__scoped_atomic_load_n)
+#undef __scoped_atomic_load_n
+#undef __scoped_atomic_store_n
+#undef __scoped_atomic_fetch_or
+#undef __scoped_atomic_fetch_and
+#endif
+#if !__has_builtin(__scoped_atomic_thread_fence)
+#undef __scoped_atomic_thread_fence
+#endif
+
+} // namespace rpc
+
+#endif // LLVM_LIBC_SHARED_RPC_H
diff --git a/libc/shared/rpc_opcodes.h b/libc/shared/rpc_opcodes.h
new file mode 100644
index 000000000000..6de41cd1899e
--- /dev/null
+++ b/libc/shared/rpc_opcodes.h
@@ -0,0 +1,53 @@
+//===-- Definition of RPC opcodes -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_RPC_OPCODES_H
+#define LLVM_LIBC_SHARED_RPC_OPCODES_H
+
+#include "rpc.h"
+
+#define LLVM_LIBC_RPC_BASE 'c'
+#define LLVM_LIBC_OPCODE(n) (LLVM_LIBC_RPC_BASE << 24 | n)
+
+typedef enum {
+  LIBC_NOOP = LLVM_LIBC_OPCODE(0),
+  LIBC_EXIT = LLVM_LIBC_OPCODE(1),
+  LIBC_WRITE_TO_STDOUT = LLVM_LIBC_OPCODE(2),
+  LIBC_WRITE_TO_STDERR = LLVM_LIBC_OPCODE(3),
+  LIBC_WRITE_TO_STREAM = LLVM_LIBC_OPCODE(4),
+  LIBC_WRITE_TO_STDOUT_NEWLINE = LLVM_LIBC_OPCODE(5),
+  LIBC_READ_FROM_STREAM = LLVM_LIBC_OPCODE(6),
+  LIBC_READ_FGETS = LLVM_LIBC_OPCODE(7),
+  LIBC_OPEN_FILE = LLVM_LIBC_OPCODE(8),
+  LIBC_CLOSE_FILE = LLVM_LIBC_OPCODE(9),
+  LIBC_MALLOC = LLVM_LIBC_OPCODE(10),
+  LIBC_FREE = LLVM_LIBC_OPCODE(11),
+  LIBC_HOST_CALL = LLVM_LIBC_OPCODE(12),
+  LIBC_ABORT = LLVM_LIBC_OPCODE(13),
+  LIBC_FEOF = LLVM_LIBC_OPCODE(14),
+  LIBC_FERROR = LLVM_LIBC_OPCODE(15),
+  LIBC_CLEARERR = LLVM_LIBC_OPCODE(16),
+  LIBC_FSEEK = LLVM_LIBC_OPCODE(17),
+  LIBC_FTELL = LLVM_LIBC_OPCODE(18),
+  LIBC_FFLUSH = LLVM_LIBC_OPCODE(19),
+  LIBC_UNGETC = LLVM_LIBC_OPCODE(20),
+  LIBC_PRINTF_TO_STDOUT = LLVM_LIBC_OPCODE(21),
+  LIBC_PRINTF_TO_STDERR = LLVM_LIBC_OPCODE(22),
+  LIBC_PRINTF_TO_STREAM = LLVM_LIBC_OPCODE(23),
+  LIBC_PRINTF_TO_STDOUT_PACKED = LLVM_LIBC_OPCODE(24),
+  LIBC_PRINTF_TO_STDERR_PACKED = LLVM_LIBC_OPCODE(25),
+  LIBC_PRINTF_TO_STREAM_PACKED = LLVM_LIBC_OPCODE(26),
+  LIBC_REMOVE = LLVM_LIBC_OPCODE(27),
+  LIBC_RENAME = LLVM_LIBC_OPCODE(28),
+  LIBC_SYSTEM = LLVM_LIBC_OPCODE(29),
+  LIBC_LAST = 0xFFFFFFFF,
+} rpc_opcode_t;
+
+#undef LLVM_LIBC_OPCODE
+
+#endif // LLVM_LIBC_SHARED_RPC_OPCODES_H
diff --git a/libc/shared/rpc_server.h b/libc/shared/rpc_server.h
new file mode 100644
index 000000000000..46e35f13f0ea
--- /dev/null
+++ b/libc/shared/rpc_server.h
@@ -0,0 +1,23 @@
+//===-- Shared RPC server interface -----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_RPC_SERVER_H
+#define LLVM_LIBC_SHARED_RPC_SERVER_H
+
+#include "libc_common.h"
+#include "src/__support/RPC/rpc_server.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using LIBC_NAMESPACE::rpc::handle_libc_opcodes;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_RPC_SERVER_H
diff --git a/libc/shared/rpc_util.h b/libc/shared/rpc_util.h
new file mode 100644
index 000000000000..687814b7ff2a
--- /dev/null
+++ b/libc/shared/rpc_util.h
@@ -0,0 +1,276 @@
+//===-- Shared memory RPC client / server utilities -------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_RPC_UTIL_H
+#define LLVM_LIBC_SHARED_RPC_UTIL_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#if (defined(__NVPTX__) || defined(__AMDGPU__)) &&                             \
+    !((defined(__CUDA__) && !defined(__CUDA_ARCH__)) ||                        \
+      (defined(__HIP__) && !defined(__HIP_DEVICE_COMPILE__)))
+#include <gpuintrin.h>
+#define RPC_TARGET_IS_GPU
+#endif
+
+// Workaround for missing __has_builtin in < GCC 10.
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+#ifndef RPC_ATTRS
+#if defined(__CUDA__) || defined(__HIP__)
+#define RPC_ATTRS __attribute__((host, device)) inline
+#else
+#define RPC_ATTRS inline
+#endif
+#endif
+
+namespace rpc {
+
+template <typename T> struct type_identity {
+  using type = T;
+};
+
+template <class T, T v> struct type_constant {
+  static inline constexpr T value = v;
+};
+
+template <class T> struct remove_reference : type_identity<T> {};
+template <class T> struct remove_reference<T &> : type_identity<T> {};
+template <class T> struct remove_reference<T &&> : type_identity<T> {};
+
+template <class T> struct is_const : type_constant<bool, false> {};
+template <class T> struct is_const<const T> : type_constant<bool, true> {};
+
+/// Freestanding implementation of std::move.
+template <class T>
+RPC_ATTRS constexpr typename remove_reference<T>::type &&move(T &&t) {
+  return static_cast<typename remove_reference<T>::type &&>(t);
+}
+
+/// Freestanding implementation of std::forward.
+template <typename T>
+RPC_ATTRS constexpr T &&forward(typename remove_reference<T>::type &value) {
+  return static_cast<T &&>(value);
+}
+template <typename T>
+RPC_ATTRS constexpr T &&forward(typename remove_reference<T>::type &&value) {
+  return static_cast<T &&>(value);
+}
+
+struct in_place_t {
+  RPC_ATTRS explicit in_place_t() = default;
+};
+
+struct nullopt_t {
+  RPC_ATTRS constexpr explicit nullopt_t() = default;
+};
+
+constexpr inline in_place_t in_place{};
+constexpr inline nullopt_t nullopt{};
+
+/// Freestanding and minimal implementation of std::optional.
+template <typename T> class optional {
+  template <typename U> struct OptionalStorage {
+    union {
+      char empty;
+      U stored_value;
+    };
+
+    bool in_use = false;
+
+    RPC_ATTRS ~OptionalStorage() { reset(); }
+
+    RPC_ATTRS constexpr OptionalStorage() : empty() {}
+
+    template <typename... Args>
+    RPC_ATTRS constexpr explicit OptionalStorage(in_place_t, Args &&...args)
+        : stored_value(forward<Args>(args)...) {}
+
+    RPC_ATTRS constexpr void reset() {
+      if (in_use)
+        stored_value.~U();
+      in_use = false;
+    }
+  };
+
+  OptionalStorage<T> storage;
+
+public:
+  RPC_ATTRS constexpr optional() = default;
+  RPC_ATTRS constexpr optional(nullopt_t) {}
+
+  RPC_ATTRS constexpr optional(const T &t) : storage(in_place, t) {
+    storage.in_use = true;
+  }
+  RPC_ATTRS constexpr optional(const optional &) = default;
+
+  RPC_ATTRS constexpr optional(T &&t) : storage(in_place, move(t)) {
+    storage.in_use = true;
+  }
+  RPC_ATTRS constexpr optional(optional &&O) = default;
+
+  RPC_ATTRS constexpr optional &operator=(T &&t) {
+    storage = move(t);
+    return *this;
+  }
+  RPC_ATTRS constexpr optional &operator=(optional &&) = default;
+
+  RPC_ATTRS constexpr optional &operator=(const T &t) {
+    storage = t;
+    return *this;
+  }
+  RPC_ATTRS constexpr optional &operator=(const optional &) = default;
+
+  RPC_ATTRS constexpr void reset() { storage.reset(); }
+
+  RPC_ATTRS constexpr const T &value() const & { return storage.stored_value; }
+
+  RPC_ATTRS constexpr T &value() & { return storage.stored_value; }
+
+  RPC_ATTRS constexpr explicit operator bool() const { return storage.in_use; }
+  RPC_ATTRS constexpr bool has_value() const { return storage.in_use; }
+  RPC_ATTRS constexpr const T *operator->() const {
+    return &storage.stored_value;
+  }
+  RPC_ATTRS constexpr T *operator->() { return &storage.stored_value; }
+  RPC_ATTRS constexpr const T &operator*() const & {
+    return storage.stored_value;
+  }
+  RPC_ATTRS constexpr T &operator*() & { return storage.stored_value; }
+
+  RPC_ATTRS constexpr T &&value() && { return move(storage.stored_value); }
+  RPC_ATTRS constexpr T &&operator*() && { return move(storage.stored_value); }
+};
+
+/// Suspend the thread briefly to assist the thread scheduler during busy loops.
+RPC_ATTRS void sleep_briefly() {
+#if __has_builtin(__nvvm_reflect)
+  if (__nvvm_reflect("__CUDA_ARCH") >= 700)
+    asm("nanosleep.u32 64;" ::: "memory");
+#elif __has_builtin(__builtin_amdgcn_s_sleep)
+  __builtin_amdgcn_s_sleep(2);
+#elif __has_builtin(__builtin_ia32_pause)
+  __builtin_ia32_pause();
+#elif __has_builtin(__builtin_arm_isb)
+  __builtin_arm_isb(0xf);
+#else
+  // Simply do nothing if sleeping isn't supported on this platform.
+#endif
+}
+
+/// Conditional to indicate if this process is running on the GPU.
+RPC_ATTRS constexpr bool is_process_gpu() {
+#ifdef RPC_TARGET_IS_GPU
+  return true;
+#else
+  return false;
+#endif
+}
+
+/// Wait for all lanes in the group to complete.
+RPC_ATTRS void sync_lane([[maybe_unused]] uint64_t lane_mask) {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_sync_lane(lane_mask);
+#endif
+}
+
+/// Copies the value from the first active thread to the rest.
+RPC_ATTRS uint32_t broadcast_value([[maybe_unused]] uint64_t lane_mask,
+                                   uint32_t x) {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_read_first_lane_u32(lane_mask, x);
+#else
+  return x;
+#endif
+}
+
+/// Returns the number lanes that participate in the RPC interface.
+RPC_ATTRS uint32_t get_num_lanes() {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_num_lanes();
+#else
+  return 1;
+#endif
+}
+
+/// Returns the id of the thread inside of an AMD wavefront executing together.
+RPC_ATTRS uint64_t get_lane_mask() {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_lane_mask();
+#else
+  return 1;
+#endif
+}
+
+/// Returns the id of the thread inside of an AMD wavefront executing together.
+RPC_ATTRS uint32_t get_lane_id() {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_lane_id();
+#else
+  return 0;
+#endif
+}
+
+/// Conditional that is only true for a single thread in a lane.
+RPC_ATTRS bool is_first_lane([[maybe_unused]] uint64_t lane_mask) {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_is_first_in_lane(lane_mask);
+#else
+  return true;
+#endif
+}
+
+/// Returns a bitmask of threads in the current lane for which \p x is true.
+RPC_ATTRS uint64_t ballot([[maybe_unused]] uint64_t lane_mask, bool x) {
+#ifdef RPC_TARGET_IS_GPU
+  return __gpu_ballot(lane_mask, x);
+#else
+  return x;
+#endif
+}
+
+/// Return \p val aligned "upwards" according to \p align.
+template <typename V, typename A>
+RPC_ATTRS constexpr V align_up(V val, A align) {
+  return ((val + V(align) - 1) / V(align)) * V(align);
+}
+
+/// Utility to provide a unified interface between the CPU and GPU's memory
+/// model. On the GPU stack variables are always private to a lane so we can
+/// simply use the variable passed in. On the CPU we need to allocate enough
+/// space for the whole lane and index into it.
+template <typename V> RPC_ATTRS V &lane_value(V *val, uint32_t id) {
+  if constexpr (is_process_gpu())
+    return *val;
+  return val[id];
+}
+
+/// Advance the \p p by \p bytes.
+template <typename T, typename U> RPC_ATTRS T *advance(T *ptr, U bytes) {
+  if constexpr (is_const<T>::value)
+    return reinterpret_cast<T *>(reinterpret_cast<const uint8_t *>(ptr) +
+                                 bytes);
+  else
+    return reinterpret_cast<T *>(reinterpret_cast<uint8_t *>(ptr) + bytes);
+}
+
+/// Wrapper around the optimal memory copy implementation for the target.
+RPC_ATTRS void rpc_memcpy(void *dst, const void *src, size_t count) {
+  __builtin_memcpy(dst, src, count);
+}
+
+template <class T> RPC_ATTRS constexpr const T &max(const T &a, const T &b) {
+  return (a < b) ? b : a;
+}
+
+} // namespace rpc
+
+#endif // LLVM_LIBC_SHARED_RPC_UTIL_H
diff --git a/libc/shared/str_to_float.h b/libc/shared/str_to_float.h
new file mode 100644
index 000000000000..dcc6027d6c77
--- /dev/null
+++ b/libc/shared/str_to_float.h
@@ -0,0 +1,28 @@
+//===-- String to float conversion utils ------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_STR_TO_FLOAT_H
+#define LLVM_LIBC_SHARED_STR_TO_FLOAT_H
+
+#include "libc_common.h"
+#include "src/__support/str_to_float.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using internal::ExpandedFloat;
+using internal::FloatConvertReturn;
+using internal::RoundDirection;
+
+using internal::binary_exp_to_float;
+using internal::decimal_exp_to_float;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_STR_TO_FLOAT_H
diff --git a/libc/shared/str_to_integer.h b/libc/shared/str_to_integer.h
new file mode 100644
index 000000000000..6ed38c932662
--- /dev/null
+++ b/libc/shared/str_to_integer.h
@@ -0,0 +1,25 @@
+//===-- String to int conversion utils --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_STR_TO_INTEGER_H
+#define LLVM_LIBC_SHARED_STR_TO_INTEGER_H
+
+#include "libc_common.h"
+#include "src/__support/str_to_integer.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using LIBC_NAMESPACE::StrToNumResult;
+
+using internal::strtointeger;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_STR_TO_INTEGER_H