[PATCH] D53460: [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

[Craig Topper via Phabricator via cfe-commits]

craig.topper created this revision.
craig.topper added reviewers: erichkeane, echristo.

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


https://reviews.llvm.org/D53460

Files:
  lib/CodeGen/CGBuiltin.cpp
  test/CodeGen/attr-target-mv.c
  test/CodeGen/builtin-cpu-supports.c


Index: test/CodeGen/builtin-cpu-supports.c
===================================================================
--- test/CodeGen/builtin-cpu-supports.c
+++ test/CodeGen/builtin-cpu-supports.c
@@ -14,7 +14,7 @@
 
   // CHECK: [[LOAD:%[^ ]+]] = load i32, i32* getelementptr inbounds ({ i32, i32, i32, [1 x i32] }, { i32, i32, i32, [1 x i32] }* @__cpu_model, i32 0, i32 3, i32 0)
   // CHECK: [[AND:%[^ ]+]] = and i32 [[LOAD]], 256
-  // CHECK: = icmp ne i32 [[AND]], 0
+  // CHECK: = icmp eq i32 [[AND]], 256
 
   return 0;
 }
Index: test/CodeGen/attr-target-mv.c
===================================================================
--- test/CodeGen/attr-target-mv.c
+++ test/CodeGen/attr-target-mv.c
@@ -70,6 +70,22 @@
 // CHECK: ret void ()* @foo_decls.sse4.2
 // CHECK: ret void ()* @foo_decls
 
+// CHECK: define void @bar4()
+// CHECK: call void @foo_multi.ifunc()
+
+// CHECK: define void ()* @foo_multi.resolver() comdat
+// CHECK: and i32 %{{.*}}, 4352
+// CHECK: icmp eq i32 %{{.*}}, 4352
+// CHECK: ret void ()* @foo_multi.fma4_sse4.2
+// CHECK: icmp eq i32 %{{.*}}, 12
+// CHECK: and i32 %{{.*}}, 4352
+// CHECK: icmp eq i32 %{{.*}}, 4352
+// CHECK: ret void ()* @foo_multi.arch_ivybridge_fma4_sse4.2
+// CHECK: and i32 %{{.*}}, 768
+// CHECK: icmp eq i32 %{{.*}}, 768
+// CHECK: ret void ()* @foo_multi.avx_sse4.2
+// CHECK: ret void ()* @foo_multi
+
 // CHECK: declare i32 @foo.arch_sandybridge()
 
 // CHECK: define available_externally i32 @foo_inline.sse4.2()
@@ -88,4 +104,3 @@
 // CHECK: define available_externally void @foo_multi.avx_sse4.2()
 // CHECK: define available_externally void @foo_multi.fma4_sse4.2()
 // CHECK: define available_externally void @foo_multi.arch_ivybridge_fma4_sse4.2()
-
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -9129,9 +9129,9 @@
       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() {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D53460.170276.patch
Type: text/x-patch
Size: 2424 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20181019/8faac631/attachment-0001.bin>