[llvm] r327829 - [MSan] Don't create zero offsets in getShadowPtrForArgument(). NFC

[Alexander Potapenko via llvm-commits]

Author: glider
Date: Mon Mar 19 03:03:47 2018
New Revision: 327829

URL: http://llvm.org/viewvc/llvm-project?rev=327829&view=rev
Log:
[MSan] Don't create zero offsets in getShadowPtrForArgument(). NFC

For MSan instrumentation with MS.ParamTLS and MS.ParamOriginTLS being
TLS variables, the CreateAdd() with ArgOffset==0 is a no-op, because
the compiler is able to fold the addition of 0.

But for KMSAN, which receives ParamTLS and ParamOriginTLS from a call
to the runtime library, this introduces a stray instruction which
complicates reading/testing the IR.

Differential revision: https://reviews.llvm.org/D44514


Modified:
    llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp?rev=327829&r1=327828&r2=327829&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp Mon Mar 19 03:03:47 2018
@@ -1094,7 +1094,8 @@ struct MemorySanitizerVisitor : public I
   Value *getShadowPtrForArgument(Value *A, IRBuilder<> &IRB,
                                  int ArgOffset) {
     Value *Base = IRB.CreatePointerCast(MS.ParamTLS, MS.IntptrTy);
-    Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
+    if (ArgOffset)
+      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
     return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
                               "_msarg");
   }
@@ -1104,7 +1105,8 @@ struct MemorySanitizerVisitor : public I
                                  int ArgOffset) {
     if (!MS.TrackOrigins) return nullptr;
     Value *Base = IRB.CreatePointerCast(MS.ParamOriginTLS, MS.IntptrTy);
-    Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
+    if (ArgOffset)
+      Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
     return IRB.CreateIntToPtr(Base, PointerType::get(MS.OriginTy, 0),
                               "_msarg_o");
   }