[X86] When checking the bits in cpu_features for function multiversioning dispatcher in the resolver, make sure all the required bits are set. Not just one of them

Summary:
The multiversioning code repurposed the code from __builtin_cpu_supports for checking if a single feature is enabled. That code essentially performed (_cpu_features & (1 << C)) != 0. But with the multiversioning path, the mask is no longer guaranteed to be a power of 2. So we return true anytime any one of the bits in the mask is set not just all of the bits.

The correct check is (_cpu_features & mask) == mask

Reviewers: erichkeane, echristo

Reviewed By: echristo

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D53460

llvm-svn: 344824

1 files changed, 3 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 7d0ec81ea22..25c39c33109 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -9129,9 +9129,9 @@ llvm::Value *CodeGenFunction::EmitX86CpuSupports(uint32_t FeaturesMask) {
       Builder.CreateAlignedLoad(CpuFeatures, CharUnits::fromQuantity(4));
 
   // Check the value of the bit corresponding to the feature requested.
-  Value *Bitset = Builder.CreateAnd(
-      Features, llvm::ConstantInt::get(Int32Ty, FeaturesMask));
-  return Builder.CreateICmpNE(Bitset, llvm::ConstantInt::get(Int32Ty, 0));
+  Value *Mask = Builder.getInt32(FeaturesMask);
+  Value *Bitset = Builder.CreateAnd(Features, Mask);
+  return Builder.CreateICmpEQ(Bitset, Mask);
 }
 
 Value *CodeGenFunction::EmitX86CpuInit() {