[msan] Workaround for invalid origins in shufflevector.

Makes origin propagation ignore literal undef operands, and,
in general, any operand we don't have origin for.

https://code.google.com/p/memory-sanitizer/issues/detail?id=56

llvm-svn: 210472

2 files changed, 27 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 93b09d32e4f..e890943c6a8 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1302,10 +1302,14 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
         if (!Origin) {
           Origin = OpOrigin;
         } else {
-          Value *FlatShadow = MSV->convertToShadowTyNoVec(OpShadow, IRB);
-          Value *Cond = IRB.CreateICmpNE(FlatShadow,
-                                         MSV->getCleanShadow(FlatShadow));
-          Origin = IRB.CreateSelect(Cond, OpOrigin, Origin);
+          Constant *ConstOrigin = dyn_cast<Constant>(OpOrigin);
+          // No point in adding something that might result in 0 origin value.
+          if (!ConstOrigin || !ConstOrigin->isNullValue()) {
+            Value *FlatShadow = MSV->convertToShadowTyNoVec(OpShadow, IRB);
+            Value *Cond =
+                IRB.CreateICmpNE(FlatShadow, MSV->getCleanShadow(FlatShadow));
+            Origin = IRB.CreateSelect(Cond, OpOrigin, Origin);
+          }
         }
       }
       return *this;
diff --git a/llvm/test/Instrumentation/MemorySanitizer/missing_origin.ll b/llvm/test/Instrumentation/MemorySanitizer/missing_origin.ll
new file mode 100644
index 00000000000..d8addce0dae
--- /dev/null
+++ b/llvm/test/Instrumentation/MemorySanitizer/missing_origin.ll
@@ -0,0 +1,19 @@
+; RUN: opt < %s -msan -msan-check-access-address=0 -msan-track-origins=1 -S | FileCheck -check-prefix=CHECK -check-prefix=CHECK %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Test that result origin is directy propagated from the argument,
+; and is not affected by all the literal undef operands.
+; https://code.google.com/p/memory-sanitizer/issues/detail?id=56
+
+define <4 x i32> @Shuffle(<4 x i32> %x) nounwind uwtable sanitize_memory {
+entry:
+  %y = shufflevector <4 x i32> %x, <4 x i32> undef, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
+  ret <4 x i32> %y
+}
+
+; CHECK-LABEL: @Shuffle(
+; CHECK: [[A:%.*]] = load i32* {{.*}}@__msan_param_origin_tls,
+; CHECK: store i32 [[A]], i32* @__msan_retval_origin_tls
+; CHECK: ret <4 x i32>