[InstCombine] Compare icmp inttoptr, inttoptr values directly

InstCombine already has some rules for `icmp ptrtoint, ptrtoint` to
drop the casts and compare the source values. This change adds the
same for the reverse case with `inttoptr`.

Author: citymarina

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -6087,12 +6087,12 @@ Instruction *InstCombinerImpl::foldICmpWithCastOp(ICmpInst &ICmp) {
 
   // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
   // integer type is the same size as the pointer type.
-  auto CompatibleSizes = [&](Type *SrcTy, Type *DestTy) {
-    if (isa<VectorType>(SrcTy)) {
-      SrcTy = cast<VectorType>(SrcTy)->getElementType();
-      DestTy = cast<VectorType>(DestTy)->getElementType();
+  auto CompatibleSizes = [&](Type *PtrTy, Type *IntTy) {
+    if (isa<VectorType>(PtrTy)) {
+      PtrTy = cast<VectorType>(PtrTy)->getElementType();
+      IntTy = cast<VectorType>(IntTy)->getElementType();
     }
-    return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
+    return DL.getPointerTypeSizeInBits(PtrTy) == IntTy->getIntegerBitWidth();
   };
   if (CastOp0->getOpcode() == Instruction::PtrToInt &&
       CompatibleSizes(SrcTy, DestTy)) {
@@ -6109,6 +6109,22 @@ Instruction *InstCombinerImpl::foldICmpWithCastOp(ICmpInst &ICmp) {
       return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
   }
 
+  // Do the same in the other direction for icmp (inttoptr x), (inttoptr/c).
+  if (CastOp0->getOpcode() == Instruction::IntToPtr &&
+      CompatibleSizes(DestTy, SrcTy)) {
+    Value *NewOp1 = nullptr;
+    if (auto *IntToPtrOp1 = dyn_cast<IntToPtrInst>(ICmp.getOperand(1))) {
+      Value *IntSrc = IntToPtrOp1->getOperand(0);
+      if (IntSrc->getType() == Op0Src->getType())
+        NewOp1 = IntToPtrOp1->getOperand(0);
+    } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
+      NewOp1 = ConstantFoldConstant(ConstantExpr::getPtrToInt(RHSC, SrcTy), DL);
+    }
+
+    if (NewOp1)
+      return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
+  }
+
   if (Instruction *R = foldICmpWithTrunc(ICmp))
     return R;
 

llvm/test/Transforms/InstCombine/icmp-inttoptr.ll

@@ -5,9 +5,7 @@ declare void @use_ptr(ptr)
 
 define i1 @inttoptr(i64 %x, i64 %y) {
 ; CHECK-LABEL: @inttoptr(
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr i64 [[X:%.*]] to ptr
-; CHECK-NEXT:    [[YPTR:%.*]] = inttoptr i64 [[Y:%.*]] to ptr
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[XPTR]], [[YPTR]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %xptr = inttoptr i64 %x to ptr
@@ -18,8 +16,7 @@ define i1 @inttoptr(i64 %x, i64 %y) {
 
 define i1 @inttoptr_constant(i64 %x) {
 ; CHECK-LABEL: @inttoptr_constant(
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr i64 [[X:%.*]] to ptr
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[XPTR]], inttoptr (i64 42 to ptr)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[X:%.*]], 42
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %xptr = inttoptr i64 %x to ptr
@@ -29,9 +26,7 @@ define i1 @inttoptr_constant(i64 %x) {
 
 define <2 x i1> @inttoptr_vector(<2 x i64> %x, <2 x i64> %y) {
 ; CHECK-LABEL: @inttoptr_vector(
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr <2 x i64> [[X:%.*]] to <2 x ptr>
-; CHECK-NEXT:    [[YPTR:%.*]] = inttoptr <2 x i64> [[Y:%.*]] to <2 x ptr>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x ptr> [[XPTR]], [[YPTR]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i64> [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %xptr = inttoptr <2 x i64> %x to <2 x ptr>
@@ -42,8 +37,7 @@ define <2 x i1> @inttoptr_vector(<2 x i64> %x, <2 x i64> %y) {
 
 define <2 x i1> @inttoptr_vector_constant(<2 x i64> %x) {
 ; CHECK-LABEL: @inttoptr_vector_constant(
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr <2 x i64> [[X:%.*]] to <2 x ptr>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x ptr> [[XPTR]], <ptr inttoptr (i64 42 to ptr), ptr inttoptr (i64 123 to ptr)>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i64> [[X:%.*]], <i64 42, i64 123>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %xptr = inttoptr <2 x i64> %x to <2 x ptr>
@@ -54,9 +48,7 @@ define <2 x i1> @inttoptr_vector_constant(<2 x i64> %x) {
 define i1 @inttoptr_size_mismatch(i200 %x, i64 %y) {
 ; CHECK-LABEL: @inttoptr_size_mismatch(
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc i200 [[X:%.*]] to i64
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr i64 [[TMP1]] to ptr
-; CHECK-NEXT:    [[YPTR:%.*]] = inttoptr i64 [[Y:%.*]] to ptr
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[XPTR]], [[YPTR]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[Y:%.*]], [[TMP1]]
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %xptr = inttoptr i200 %x to ptr
@@ -67,8 +59,7 @@ define i1 @inttoptr_size_mismatch(i200 %x, i64 %y) {
 
 define <2 x i1> @inttoptr_vector_constant_size_mismatch(<2 x i64> %x) {
 ; CHECK-LABEL: @inttoptr_vector_constant_size_mismatch(
-; CHECK-NEXT:    [[XPTR:%.*]] = inttoptr <2 x i64> [[X:%.*]] to <2 x ptr>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x ptr> [[XPTR]], <ptr inttoptr (i9 42 to ptr), ptr inttoptr (i9 123 to ptr)>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i64> [[X:%.*]], <i64 42, i64 123>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %xptr = inttoptr <2 x i64> %x to <2 x ptr>
@@ -93,7 +84,7 @@ define i1 @inttoptr_used(i64 %x, i64 %y) {
 ; CHECK-NEXT:    [[YPTR:%.*]] = inttoptr i64 [[Y:%.*]] to ptr
 ; CHECK-NEXT:    call void @use_ptr(ptr [[XPTR]])
 ; CHECK-NEXT:    call void @use_ptr(ptr [[YPTR]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt ptr [[XPTR]], [[YPTR]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[X]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %xptr = inttoptr i64 %x to ptr