[libc][NFC] Detect host CPU features using try_compile instead of try_run.

gchatelet · gchatelet · commit 9acc2f37bdfc · 2023-01-23T09:05:53.000Z
This implements the same behavior as D141997 but makes sure that the same detection mechanism is used between CMake and source code. Differential Revision: https://reviews.llvm.org/D142108
diff --git a/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake b/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake
@@ -44,44 +44,32 @@ function(_intersection output_var list1 list2)
   set(${output_var} ${tmp} PARENT_SCOPE)
 endfunction()
 
-# Generates a cpp file to introspect the compiler defined flags.
-function(_generate_check_code)
+set(AVAILABLE_CPU_FEATURES "")
+if(LIBC_CROSSBUILD)
+  # If we are doing a cross build, we will just assume that all CPU features
+  # are available.
+  set(AVAILABLE_CPU_FEATURES ${ALL_CPU_FEATURES})
+else()
+  # Try compile a C file to check if flag is supported.
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
   foreach(feature IN LISTS ALL_CPU_FEATURES)
-    set(DEFINITIONS
-        "${DEFINITIONS}
-#ifdef __${feature}__
-    \"${feature}\",
-#endif")
+    try_compile(
+      has_feature
+      ${CMAKE_CURRENT_BINARY_DIR}/cpu_features
+      SOURCES ${LIBC_SOURCE_DIR}/cmake/modules/cpu_features/check_${feature}.cpp
+      COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${LIBC_COMPILE_OPTIONS_NATIVE}
+    )
+    if(has_feature)
+      list(APPEND AVAILABLE_CPU_FEATURES ${feature})
+    endif()
   endforeach()
-  configure_file(
-    "${LIBC_SOURCE_DIR}/cmake/modules/cpu_features/check_cpu_features.cpp.in"
-    "cpu_features/check_cpu_features.cpp" @ONLY)
-endfunction()
-_generate_check_code()
+endif()
 
-set(LIBC_CPU_FEATURES "" CACHE PATH "Host supported CPU features")
+set(LIBC_CPU_FEATURES ${AVAILABLE_CPU_FEATURES} CACHE STRING "Host supported CPU features")
 
-if(LIBC_CROSSBUILD)
-  _intersection(cpu_features "${ALL_CPU_FEATURES}" "${LIBC_CPU_FEATURES}")
-  if(NOT "${cpu_features}" STREQUAL "${LIBC_CPU_FEATURES}")
-    message(FATAL_ERROR "Unsupported CPU features: ${cpu_features}")
-  endif()
-  message(STATUS "Set CPU features: ${cpu_features}")
-  set(LIBC_CPU_FEATURES "${cpu_features}")
+_intersection(cpu_features "${AVAILABLE_CPU_FEATURES}" "${LIBC_CPU_FEATURES}")
+if(NOT "${cpu_features}" STREQUAL "${LIBC_CPU_FEATURES}")
+  message(FATAL_ERROR "Unsupported CPU features: ${cpu_features}")
 else()
-  # Populates the LIBC_CPU_FEATURES list from host.
-  try_run(
-    run_result compile_result "${CMAKE_CURRENT_BINARY_DIR}/check_${feature}"
-    "${CMAKE_CURRENT_BINARY_DIR}/cpu_features/check_cpu_features.cpp"
-    COMPILE_DEFINITIONS ${LIBC_COMPILE_OPTIONS_NATIVE}
-    COMPILE_OUTPUT_VARIABLE compile_output
-    RUN_OUTPUT_VARIABLE run_output)
-  if("${run_result}" EQUAL 0)
-    message(STATUS "Set CPU features: ${run_output}")
-    set(LIBC_CPU_FEATURES "${run_output}")
-  elseif(NOT ${compile_result})
-    message(FATAL_ERROR "Failed to compile: ${compile_output}")
-  else()
-    message(FATAL_ERROR "Failed to run: ${run_output}")
-  endif()
+  message(STATUS "Set CPU features: ${cpu_features}")
 endif()
diff --git a/libc/cmake/modules/cpu_features/check_AVX2.cpp b/libc/cmake/modules/cpu_features/check_AVX2.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_AVX2
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_AVX512BW.cpp b/libc/cmake/modules/cpu_features/check_AVX512BW.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_AVX512BW
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_AVX512F.cpp b/libc/cmake/modules/cpu_features/check_AVX512F.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_AVX512F
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_FMA.cpp b/libc/cmake/modules/cpu_features/check_FMA.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_FMA
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_SSE2.cpp b/libc/cmake/modules/cpu_features/check_SSE2.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_SSE2
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_SSE4_2.cpp b/libc/cmake/modules/cpu_features/check_SSE4_2.cpp
@@ -0,0 +1,5 @@
+#include "src/__support/cpu_features.h"
+
+#ifndef LIBC_TARGET_HAS_SSE4_2
+#error unsupported
+#endif
diff --git a/libc/cmake/modules/cpu_features/check_cpu_features.cpp.in b/libc/cmake/modules/cpu_features/check_cpu_features.cpp.in
diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
@@ -33,6 +33,7 @@ add_header_library(
   HDRS
     architectures.h
     common.h
+    cpu_features.h
     endian.h
 )
 
diff --git a/libc/src/__support/FPUtil/FMA.h b/libc/src/__support/FPUtil/FMA.h
@@ -11,6 +11,7 @@
 
 #include "src/__support/architectures.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #if defined(LIBC_TARGET_HAS_FMA)
 
diff --git a/libc/src/__support/FPUtil/aarch64/FMA.h b/libc/src/__support/FPUtil/aarch64/FMA.h
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_SRC_SUPPORT_FPUTIL_AARCH64_FMA_H
 
 #include "src/__support/architectures.h"
+#include "src/__support/cpu_features.h"
 
 #if !defined(LLVM_LIBC_ARCH_AARCH64)
 #error "Invalid include"
diff --git a/libc/src/__support/FPUtil/multiply_add.h b/libc/src/__support/FPUtil/multiply_add.h
@@ -11,6 +11,7 @@
 
 #include "src/__support/architectures.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 namespace __llvm_libc {
 namespace fputil {
diff --git a/libc/src/__support/FPUtil/x86_64/FMA.h b/libc/src/__support/FPUtil/x86_64/FMA.h
@@ -11,6 +11,7 @@
 
 #include "src/__support/architectures.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #if !defined(LLVM_LIBC_ARCH_X86_64)
 #error "Invalid include"
diff --git a/libc/src/__support/architectures.h b/libc/src/__support/architectures.h
@@ -49,12 +49,4 @@
 #define LLVM_LIBC_ARCH_ANY_ARM
 #endif
 
-#if defined(LLVM_LIBC_ARCH_AARCH64)
-#define LIBC_TARGET_HAS_FMA
-#elif defined(LLVM_LIBC_ARCH_X86_64)
-#if (defined(__AVX2__) || defined(__FMA__))
-#define LIBC_TARGET_HAS_FMA
-#endif
-#endif
-
 #endif // LLVM_LIBC_SUPPORT_ARCHITECTURES_H
diff --git a/libc/src/__support/cpu_features.h b/libc/src/__support/cpu_features.h
@@ -0,0 +1,43 @@
+//===-- Compile time cpu feature detection ----------------------*- 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 lists target cpu features by introspecting compiler enabled
+// preprocessor definitions.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SUPPORT_CPU_FEATURES_H
+#define LLVM_LIBC_SRC_SUPPORT_CPU_FEATURES_H
+
+#if defined(__SSE2__)
+#define LIBC_TARGET_HAS_SSE2
+#endif
+
+#if defined(__SSE4_2__)
+#define LIBC_TARGET_HAS_SSE4_2
+#endif
+
+#if defined(__AVX__)
+#define LIBC_TARGET_HAS_AVX
+#endif
+
+#if defined(__AVX2__)
+#define LIBC_TARGET_HAS_AVX2
+#endif
+
+#if defined(__AVX512F__)
+#define LIBC_TARGET_HAS_AVX512F
+#endif
+
+#if defined(__AVX512BW__)
+#define LIBC_TARGET_HAS_AVX512BW
+#endif
+
+#if defined(__ARM_FEATURE_FMA) || defined(__AVX2__)
+#define LIBC_TARGET_HAS_FMA
+#endif
+
+#endif // LLVM_LIBC_SRC_SUPPORT_CPU_FEATURES_H
diff --git a/libc/src/math/generic/asinf.cpp b/libc/src/math/generic/asinf.cpp
@@ -13,6 +13,7 @@
 #include "src/__support/FPUtil/except_value_utils.h"
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/cosf.cpp b/libc/src/math/generic/cosf.cpp
@@ -14,6 +14,7 @@
 #include "src/__support/FPUtil/except_value_utils.h"
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/expm1f.cpp b/libc/src/math/generic/expm1f.cpp
@@ -16,6 +16,7 @@
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/FPUtil/nearest_integer.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/sincosf.cpp b/libc/src/math/generic/sincosf.cpp
@@ -12,6 +12,7 @@
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/sincosf_utils.h b/libc/src/math/generic/sincosf_utils.h
@@ -12,6 +12,7 @@
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PolyEval.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #if defined(LIBC_TARGET_HAS_FMA)
 #include "range_reduction_fma.h"
diff --git a/libc/src/math/generic/sinf.cpp b/libc/src/math/generic/sinf.cpp
@@ -14,6 +14,7 @@
 #include "src/__support/FPUtil/PolyEval.h"
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/tanf.cpp b/libc/src/math/generic/tanf.cpp
@@ -15,6 +15,7 @@
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/FPUtil/nearest_integer.h"
 #include "src/__support/common.h"
+#include "src/__support/cpu_features.h"
 
 #include <errno.h>
 
diff --git a/libc/src/math/generic/tanhf.cpp b/libc/src/math/generic/tanhf.cpp
@@ -8,6 +8,7 @@
 
 #include "src/math/tanhf.h"
 #include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/cpu_features.h"
 #include "src/math/generic/explogxf.h"
 
 namespace __llvm_libc {
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -79,6 +79,7 @@ libc_support_library(
     hdrs = [
         "src/__support/architectures.h",
         "src/__support/common.h",
+        "src/__support/cpu_features.h",
         "src/__support/endian.h",
     ],
 )

Original file line number	Diff line number	Diff line change
`@@ -33,6 +33,7 @@ add_header_library(`
`33`	`33`	`HDRS`
`34`	`34`	`architectures.h`
`35`	`35`	`common.h`
	`36`	`+ cpu_features.h`
`36`	`37`	`endian.h`
`37`	`38`	`)`
`38`	`39`