[llvm] [InstCombine] Fold `icmp pred (inttoptr X), (inttoptr Y) -> icmp pred X, Y` (PR #77832)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

Alive2 proofs are unavailable because `inttoptr` is unsupported.


---
Full diff: https://github.com/llvm/llvm-project/pull/77832.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+9) 
- (modified) llvm/test/Transforms/InstCombine/cast_ptr.ll (+45) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7c1aff445524de..da94bb1d2a8f36 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5703,6 +5703,15 @@ Instruction *InstCombinerImpl::foldICmpWithCastOp(ICmpInst &ICmp) {
       return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
   }
 
+  // Turn icmp pred (inttoptr x), (inttoptr y) into icmp pred x, y
+  if (CastOp0->getOpcode() == Instruction::IntToPtr &&
+      CompatibleSizes(DestTy, SrcTy)) {
+    Value *Op1Src;
+    if (match(ICmp.getOperand(1), m_IntToPtr(m_Value(Op1Src))) &&
+        Op1Src->getType() == SrcTy)
+      return new ICmpInst(ICmp.getPredicate(), Op0Src, Op1Src);
+  }
+
   if (Instruction *R = foldICmpWithTrunc(ICmp))
     return R;
 
diff --git a/llvm/test/Transforms/InstCombine/cast_ptr.ll b/llvm/test/Transforms/InstCombine/cast_ptr.ll
index 5c6c012064e05b..8865af0a34a401 100644
--- a/llvm/test/Transforms/InstCombine/cast_ptr.ll
+++ b/llvm/test/Transforms/InstCombine/cast_ptr.ll
@@ -113,6 +113,51 @@ define i1 @test4(i32 %A) {
   ret i1 %C
 }
 
+define i1 @test4_icmp_with_var(i32 %A1, i32 %A2) {
+; CHECK-LABEL: @test4_icmp_with_var(
+; CHECK-NEXT:    [[C:%.*]] = icmp ugt i32 [[A1:%.*]], [[A2:%.*]]
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %B1 = inttoptr i32 %A1 to ptr
+  %B2 = inttoptr i32 %A2 to ptr
+  %C = icmp ugt ptr %B1, %B2
+  ret i1 %C
+}
+
+define i1 @test4_cmp_with_nonnull_constant(i32 %A) {
+; CHECK-LABEL: @test4_cmp_with_nonnull_constant(
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i32 [[A:%.*]], 1
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %B = inttoptr i32 %A to ptr
+  %C = icmp eq ptr %B, inttoptr (i32 1 to ptr)
+  ret i1 %C
+}
+
+define i1 @test4_cmp_eq_0_or_1(i32 %x) {
+; CHECK-LABEL: @test4_cmp_eq_0_or_1(
+; CHECK-NEXT:    [[OR:%.*]] = icmp ult i32 [[X:%.*]], 2
+; CHECK-NEXT:    ret i1 [[OR]]
+;
+  %cast = inttoptr i32 %x to ptr
+  %tobool = icmp eq i32 %x, 0
+  %cmp = icmp eq ptr %cast, inttoptr (i32 1 to ptr)
+  %or = or i1 %tobool, %cmp
+  ret i1 %or
+}
+
+define i1 @test4_icmp_with_var_mismatched_type(i32 %A1, i64 %A2) {
+; CHECK-LABEL: @test4_icmp_with_var_mismatched_type(
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc i64 [[A2:%.*]] to i32
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[TMP1]], [[A1:%.*]]
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %B1 = inttoptr i32 %A1 to ptr
+  %B2 = inttoptr i64 %A2 to ptr
+  %C = icmp ugt ptr %B1, %B2
+  ret i1 %C
+}
+
 define i1 @test4_as2(i16 %A) {
 ; CHECK-LABEL: @test4_as2(
 ; CHECK-NEXT:    [[C:%.*]] = icmp eq i16 [[A:%.*]], 0

``````````

</details>


https://github.com/llvm/llvm-project/pull/77832