[libcxx-commits] [libcxx] [libcxx] Set `_LIBCPP_HAS_CLOCK_GETTIME` for GPU targets (PR #99243)

[Joseph Huber via libcxx-commits]

https://github.com/jhuber6 updated https://github.com/llvm/llvm-project/pull/99243

>From aab10be6c0fdd7702f5cf716daf7c2b968f44541 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Tue, 16 Jul 2024 16:20:24 -0500
Subject: [PATCH] [libcxx] Set `_LIBCPP_HAS_CLOCK_GETTIME` for GPU targets

Summary:
I am attempting to get the GPU to build and support libc++. One issue
I've encountered is that it will look for `timeval` unless this macro is
set. We can support `CLOCK_MONOTONIC` on the GPU fairly easily as we
have access to a fixed-frequency clock via `__builtin_readsteadycounter`
intrinsics with a known frequency. This also requires `CLOCK_REALTIME`
which we can't support, but provide anyway from the GPU `libc` to make
this happy. It will return an error so at least that will be obvious.

I may need a more consistent configuration for this in the future, maybe
I should put a common macro in a different common header that's just
`__GPU__`? I don't know where I would put such a thing however.
---
 libcxx/src/chrono.cpp                      | 5 +++--
 libcxx/src/filesystem/filesystem_clock.cpp | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/libcxx/src/chrono.cpp b/libcxx/src/chrono.cpp
index 83e8a64504ae0..986360d0368a0 100644
--- a/libcxx/src/chrono.cpp
+++ b/libcxx/src/chrono.cpp
@@ -31,9 +31,10 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
-// OpenBSD does not have a fully conformant suite of POSIX timers, but
+// OpenBSD and GPU do not have a fully conformant suite of POSIX timers, but
 // it does have clock_gettime and CLOCK_MONOTONIC which is all we need.
-#if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__OpenBSD__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
+#if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__OpenBSD__) || defined(__AMDGPU__) ||                      \
+    defined(__NVPTX__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
 #  define _LIBCPP_HAS_CLOCK_GETTIME
 #endif
 
diff --git a/libcxx/src/filesystem/filesystem_clock.cpp b/libcxx/src/filesystem/filesystem_clock.cpp
index e13b2853e367c..473a54a00f013 100644
--- a/libcxx/src/filesystem/filesystem_clock.cpp
+++ b/libcxx/src/filesystem/filesystem_clock.cpp
@@ -29,7 +29,8 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
-#if defined(__APPLE__) || defined(__gnu_hurd__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
+#if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__AMDGPU__) || defined(__NVPTX__) ||                        \
+    (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
 #  define _LIBCPP_HAS_CLOCK_GETTIME
 #endif