[X86] Enable isel to use the PAUSE instruction even when SSE2 is disabled. Clang...

Summary:
On older processors this instruction encoding is treated as a NOP.

MSVC doesn't disable intrinsics based on features the way clang/gcc does. Because the PAUSE instruction encoding doesn't crash older processors, some software out there uses these intrinsics without checking for SSE2.

This change also seems to also be consistent with gcc behavior.

Fixes PR34079

Reviewers: RKSimon, zvi

Reviewed By: RKSimon

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D36362

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@310191 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/BuiltinsX86.def b/include/clang/Basic/BuiltinsX86.def
index a516bf6bf06c618dac8108ead204ac0d99c29d62..6d3a478ac360c6e999ab42bce432a1730c51c5fc 100644 (file)
--- a/include/clang/Basic/BuiltinsX86.def
+++ b/include/clang/Basic/BuiltinsX86.def
@@ -338,8 +338,8 @@ TARGET_BUILTIN(__builtin_ia32_lfence, "v", "", "sse2")
 TARGET_HEADER_BUILTIN(_mm_lfence, "v", "h", "emmintrin.h", ALL_LANGUAGES, "sse2")
 TARGET_BUILTIN(__builtin_ia32_mfence, "v", "", "sse2")
 TARGET_HEADER_BUILTIN(_mm_mfence, "v", "h", "emmintrin.h", ALL_LANGUAGES, "sse2")
-TARGET_BUILTIN(__builtin_ia32_pause, "v", "", "sse2")
-TARGET_HEADER_BUILTIN(_mm_pause, "v", "h", "emmintrin.h", ALL_LANGUAGES, "sse2")
+TARGET_BUILTIN(__builtin_ia32_pause, "v", "", "")
+TARGET_HEADER_BUILTIN(_mm_pause, "v", "h", "emmintrin.h", ALL_LANGUAGES, "")
 TARGET_BUILTIN(__builtin_ia32_pmuludq128, "V2LLiV4iV4i", "", "sse2")
 TARGET_BUILTIN(__builtin_ia32_psraw128, "V8sV8sV8s", "", "sse2")
 TARGET_BUILTIN(__builtin_ia32_psrad128, "V4iV4iV4i", "", "sse2")

diff --git a/test/CodeGen/pause.c b/test/CodeGen/pause.c
new file mode 100644 (file)
index 0000000..1a8e10a
--- /dev/null
+++ b/test/CodeGen/pause.c
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -ffreestanding %s -triple=i386-pc-win32 -target-feature -sse2 -emit-llvm -o - -Wall -Werror | FileCheck %s
+// RUN: %clang_cc1 -ffreestanding %s -triple=i386-pc-win32 -target-feature +sse2 -emit-llvm -o - -Wall -Werror | FileCheck %s
+
+
+#include <x86intrin.h>
+
+void test_mm_pause() {
+  // CHECK-LABEL: test_mm_pause
+  // CHECK: call void @llvm.x86.sse2.pause()
+  return _mm_pause();
+}