[llvm-commits] [llvm] r84175 - /llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

[Nick Lewycky]

Author: nicholas
Date: Thu Oct 15 02:11:24 2009
New Revision: 84175

URL: http://llvm.org/viewvc/llvm-project?rev=84175&view=rev
Log:
Teach basicaa about memcpy/memmove/memset. The length argument can be used to
improve alias results if constant, and the source pointer can't be modified.

Modified:
    llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=84175&r1=84174&r2=84175&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Thu Oct 15 02:11:24 2009
@@ -310,6 +310,28 @@
     if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
       switch (II->getIntrinsicID()) {
       default: break;
+      case Intrinsic::memcpy:
+      case Intrinsic::memmove: {
+        unsigned Len = ~0U;
+        if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3)))
+          Len = LenCI->getZExtValue();
+        Value *Dest = II->getOperand(1);
+        Value *Src = II->getOperand(2);
+        if (alias(Dest, Len, P, Size) == NoAlias) {
+          if (alias(Src, Len, P, Size) == NoAlias)
+            return NoModRef;
+          return Ref;
+        }
+        }
+        break;
+      case Intrinsic::memset:
+        if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3))) {
+          unsigned Len = LenCI->getZExtValue();
+          Value *Dest = II->getOperand(1);
+          if (alias(Dest, Len, P, Size) == NoAlias)
+            return NoModRef;
+        }
+        break;
       case Intrinsic::atomic_cmp_swap:
       case Intrinsic::atomic_swap:
       case Intrinsic::atomic_load_add: