[PATCH] D44514: [MSan] Don't create zero offsets in getShadowPtrForArgument(). NFC

[Alexander Potapenko via Phabricator via llvm-commits]

glider created this revision.
glider added reviewers: dvyukov, vitalybuka.
Herald added a subscriber: llvm-commits.

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.


Repository:
  rL LLVM

https://reviews.llvm.org/D44514

Files:
  lib/Transforms/Instrumentation/MemorySanitizer.cpp


Index: lib/Transforms/Instrumentation/MemorySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1096,7 +1096,8 @@
   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");
   }
@@ -1106,7 +1107,8 @@
                                  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");
   }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D44514.138534.patch
Type: text/x-patch
Size: 1218 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180315/63758f26/attachment.bin>