[InstSimplify] Try hard to simplify pointer comparisons

Simplify ptrtoint comparisons involving operands with different source
types.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277951 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/InstructionSimplify.cpp

@@ -3094,6 +3094,16 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   if (LHS->getType()->isPointerTy())
     if (auto *C = computePointerICmp(Q.DL, Q.TLI, Q.DT, Pred, Q.CxtI, LHS, RHS))
       return C;
+  if (auto *CLHS = dyn_cast<PtrToIntOperator>(LHS))
+    if (auto *CRHS = dyn_cast<PtrToIntOperator>(RHS))
+      if (Q.DL.getTypeSizeInBits(CLHS->getPointerOperandType()) ==
+              Q.DL.getTypeSizeInBits(CLHS->getType()) &&
+          Q.DL.getTypeSizeInBits(CRHS->getPointerOperandType()) ==
+              Q.DL.getTypeSizeInBits(CRHS->getType()))
+        if (auto *C = computePointerICmp(Q.DL, Q.TLI, Q.DT, Pred, Q.CxtI,
+                                         CLHS->getPointerOperand(),
+                                         CRHS->getPointerOperand()))
+          return C;
 
   if (GetElementPtrInst *GLHS = dyn_cast<GetElementPtrInst>(LHS)) {
     if (GEPOperator *GRHS = dyn_cast<GEPOperator>(RHS)) {

test/Transforms/InstSimplify/compare.ll

@@ -206,6 +206,19 @@ define i1 @gep16(i8* %ptr, i32 %a) {
 ; CHECK-NEXT: ret i1 false
 }
 
+define i1 @gep17() {
+; CHECK-LABEL: @gep17(
+  %alloca = alloca i32, align 4
+  %bc = bitcast i32* %alloca to [4 x i8]*
+  %gep1 = getelementptr inbounds i32, i32* %alloca, i32 1
+  %pti1 = ptrtoint i32* %gep1 to i32
+  %gep2 = getelementptr inbounds [4 x i8], [4 x i8]* %bc, i32 0, i32 1
+  %pti2 = ptrtoint i8* %gep2 to i32
+  %cmp = icmp ugt i32 %pti1, %pti2
+  ret i1 %cmp
+; CHECK-NEXT: ret i1 true
+}
+
 define i1 @zext(i32 %x) {
 ; CHECK-LABEL: @zext(
   %e1 = zext i32 %x to i64