[libc-commits] [libc] [libc] Allow hermetic timing if the `clock` function is built (PR #71092)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/71092

Summary:
This patch fixes some code duplication on the GPU. The GPU build wanted
to enable timing for hermetic tests so it built some special case
handling into the test suite. Now that `clock` is supported on the
target we can simply link against the external interface. Because we
include `clock.h` for the CLOCKS_PER_SEC macro we remap the C entrypoint
to the internal one if it ends up called. This should allow hermetic
tests to run with timing if it is supported.


>From ad0fd6ecaf4726023fefe5be13e37f4e13d1d389 Mon Sep 17 00:00:00 2001
From: Joseph Huber <jhuber6 at vols.utk.edu>
Date: Thu, 2 Nov 2023 13:39:09 -0500
Subject: [PATCH] [libc] Allow hermetic timing if the `clock` function is built

Summary:
This patch fixes some code duplication on the GPU. The GPU build wanted
to enable timing for hermetic tests so it built some special case
handling into the test suite. Now that `clock` is supported on the
target we can simply link against the external interface. Because we
include `clock.h` for the CLOCKS_PER_SEC macro we remap the C entrypoint
to the internal one if it ends up called. This should allow hermetic
tests to run with timing if it is supported.
---
 libc/cmake/modules/LLVMLibCTestRules.cmake |  6 ++++++
 libc/test/UnitTest/CMakeLists.txt          |  3 +++
 libc/test/UnitTest/LibcTest.cpp            | 22 +++++++---------------
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/libc/cmake/modules/LLVMLibCTestRules.cmake b/libc/cmake/modules/LLVMLibCTestRules.cmake
index fc66c129609456e..f7ca6a2e7021141 100644
--- a/libc/cmake/modules/LLVMLibCTestRules.cmake
+++ b/libc/cmake/modules/LLVMLibCTestRules.cmake
@@ -636,6 +636,12 @@ function(add_libc_hermetic_test test_name)
       libc.src.string.memset
       libc.src.__support.StringUtil.error_to_string
   )
+
+  if(TARGET libc.src.time.clock)
+    # We will link in the 'clock' implementation if it exists for test timing.
+    list(APPEND fq_deps_list libc.src.time.clock)
+  endif()
+
   list(REMOVE_DUPLICATES fq_deps_list)
 
   # TODO: Instead of gathering internal object files from entrypoints,
diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
index 4d384535581267d..9baa41874a83dba 100644
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -28,6 +28,9 @@ function(add_unittest_framework_library name)
     )
     target_include_directories(${lib} PUBLIC ${LIBC_SOURCE_DIR})
     target_compile_options(${lib} PRIVATE -fno-exceptions -fno-rtti)
+    if(TARGET libc.src.time.clock)
+      target_compile_definitions(${lib} PRIVATE TARGET_SUPPORTS_CLOCK)
+    endif()
   endforeach()
   target_include_directories(${name}.hermetic PRIVATE ${LIBC_BUILD_DIR}/include)
   target_compile_options(${name}.hermetic
diff --git a/libc/test/UnitTest/LibcTest.cpp b/libc/test/UnitTest/LibcTest.cpp
index 5c27e2e69bead95..3fba95f88f0fb3e 100644
--- a/libc/test/UnitTest/LibcTest.cpp
+++ b/libc/test/UnitTest/LibcTest.cpp
@@ -15,20 +15,12 @@
 
 #if __STDC_HOSTED__
 #include <time.h>
-#elif defined(LIBC_TARGET_ARCH_IS_GPU)
-#include "src/__support/GPU/utils.h"
-static long clock() { return LIBC_NAMESPACE::gpu::fixed_frequency_clock(); }
-#if defined(LIBC_TARGET_ARCH_IS_NVPTX)
-#define CLOCKS_PER_SEC 1000000000UL
-#else
-// The AMDGPU loader needs to initialize this at runtime by querying the driver.
-extern "C" [[gnu::visibility("protected")]] uint64_t
-    [[clang::address_space(4)]] __llvm_libc_clock_freq;
-#define CLOCKS_PER_SEC __llvm_libc_clock_freq
-#endif
-#else
-static long clock() { return 0; }
-#define CLOCKS_PER_SEC 1
+#define LIBC_TEST_USE_CLOCK
+#elif defined(TARGET_SUPPORTS_CLOCK)
+#include <time.h>
+#include "src/time/clock.h"
+extern "C" clock_t clock() noexcept { return LIBC_NAMESPACE::clock(); }
+#define LIBC_TEST_USE_CLOCK
 #endif
 
 namespace LIBC_NAMESPACE {
@@ -147,7 +139,7 @@ int Test::runTests(const char *TestFilter) {
       break;
     case RunContext::RunResult::Pass:
       tlog << GREEN << "[       OK ] " << RESET << TestName;
-#if __STDC_HOSTED__ || defined(LIBC_TARGET_ARCH_IS_GPU)
+#ifdef LIBC_TEST_USE_CLOCK
       tlog << " (took ";
       if (start_time > end_time) {
         tlog << "unknown - try rerunning)\n";