Make this transformation slightly less agressive and more correct.

The 'CmpInst::isFalseWhenEqual' function returns 'false' for values other than
simply equality. For instance, it returns 'false' for <= or >=. This isn't the
correct behavior for this transformation, which is checking for strict equality
and non-equality. It was causing the gcc.c-torture/execute/frame-address.c test
to fail because it would completely (and incorrectly) optimize a whole function
into a 'ret i32 0'.

llvm-svn: 152497

1 files changed, 18 insertions, 8 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index c024e9260b1..95fd48ee658 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1609,23 +1609,33 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
     if (llvm::isKnownNonNull(LHSPtr) || llvm::isKnownNonNull(RHSPtr)) {
       // If both sides are different identified objects, they aren't equal
       // unless they're null.
-      if (LHSPtr != RHSPtr && llvm::isIdentifiedObject(RHSPtr))
-        return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
+      if (LHSPtr != RHSPtr && llvm::isIdentifiedObject(RHSPtr) &&
+          (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::FCMP_UEQ))
+        return ConstantInt::get(ITy, false);
 
       // A local identified object (alloca or noalias call) can't equal any
       // incoming argument, unless they're both null.
-      if (isa<Instruction>(LHSPtr) && isa<Argument>(RHSPtr))
-        return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
+      if (isa<Instruction>(LHSPtr) && isa<Argument>(RHSPtr) &&
+          (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::FCMP_UEQ))
+        return ConstantInt::get(ITy, false);
     }
 
     // Assume that the constant null is on the right.
-    if (llvm::isKnownNonNull(LHSPtr) && isa<ConstantPointerNull>(RHSPtr))
-      return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
+    if (llvm::isKnownNonNull(LHSPtr) && isa<ConstantPointerNull>(RHSPtr)) {
+      if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::FCMP_UEQ)
+        return ConstantInt::get(ITy, false);
+      else if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::FCMP_ONE)
+        return ConstantInt::get(ITy, true);
+    }
   } else if (isa<Argument>(LHSPtr)) {
     RHSPtr = RHSPtr->stripInBoundsOffsets();
     // An alloca can't be equal to an argument.
-    if (isa<AllocaInst>(RHSPtr))
-      return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
+    if (isa<AllocaInst>(RHSPtr)) {
+      if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::FCMP_UEQ)
+        return ConstantInt::get(ITy, false);
+      else if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::FCMP_ONE)
+        return ConstantInt::get(ITy, true);
+    }
   }
 
   // If we are comparing with zero then try hard since this is a common case.