Fix a rather nasty regression from r150690: LHS != RHS does not imply…

… LHS->stripPointerCasts() != RHS->stripPointerCasts().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150863 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/InstructionSimplify.cpp

@@ -1593,10 +1593,11 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   // the compare, and if only one of them is then we moved it to RHS already.
   Value *LHSPtr = LHS->stripPointerCasts();
   Value *RHSPtr = RHS->stripPointerCasts();
+  if (LHSPtr == RHSPtr)
+    return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
   if (isa<AllocaInst>(LHSPtr) && (isa<GlobalValue>(RHSPtr) ||
                                   isa<AllocaInst>(RHSPtr)  ||
                                   isa<ConstantPointerNull>(RHSPtr)))
-    // We already know that LHS != RHS.
     return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
 
   // If we are comparing with zero then try hard since this is a common case.

test/Transforms/InstSimplify/compare.ll

@@ -30,6 +30,16 @@ define i1 @gep() {
 ; CHECK-NEXT: ret i1 false
 }
 
+define i1 @gep2() {
+; CHECK: @gep2
+  %a = alloca [3 x i8], align 8
+  %x = getelementptr inbounds [3 x i8]* %a, i32 0, i32 0
+  %y = getelementptr inbounds [3 x i8]* %a, i32 0, i32 0
+  %cmp = icmp eq i8* %x, %y
+  ret i1 %cmp
+; CHECK-NEXT: ret i1 true
+}
+
 define i1 @zext(i32 %x) {
 ; CHECK: @zext
   %e1 = zext i32 %x to i64