From: Craig Topper <craig.topper@intel.com>
Date: Sat, 5 Aug 2017 23:35:54 +0000 (+0000)
Subject: [X86] Enable isel to use the PAUSE instruction even when SSE2 is disabled. Clang... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c5d8b4291b0b4844d28f241540f6205584b14051;p=clang

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

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 a516bf6bf0..6d3a478ac3 100644
--- 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
index 0000000000..1a8e10aec0
--- /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();
+}