[IR] Add support for samesign in Operator::hasPoisonGeneratingFlags

[dtcxzyw]

Fix #112356. Sorry about that...

[llvmbot]

@llvm/pr-subscribers-llvm-ir

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

Changes

Fix #112356. Sorry about that...

---

Full diff: https://github.com/llvm/llvm-project/pull/112358.diff

2 Files Affected:

• (modified) llvm/lib/IR/Operator.cpp (+2)
• (modified) llvm/test/Transforms/InstCombine/icmp.ll (+11)

diff --git a/llvm/lib/IR/Operator.cpp b/llvm/lib/IR/Operator.cpp
index f93ff8f6fc8a25..199eb4d90f5565 100644
--- a/llvm/lib/IR/Operator.cpp
+++ b/llvm/lib/IR/Operator.cpp
@@ -50,6 +50,8 @@ bool Operator::hasPoisonGeneratingFlags() const {
     if (auto *NNI = dyn_cast<PossiblyNonNegInst>(this))
       return NNI->hasNonNeg();
     return false;
+  case Instruction::ICmp:
+    return cast<ICmpInst>(this)->hasSameSign();
   default:
     if (const auto *FP = dyn_cast<FPMathOperator>(this))
       return FP->hasNoNaNs() || FP->hasNoInfs();
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index ecf21b8a42cf50..bfe70f992b8457 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -5365,3 +5365,14 @@ define i1 @icmp_and_inv_pow2_or_zero_ne_0(i32 %A, i32 %B) {
   %cmp = icmp ne i32 %and, 0
   ret i1 %cmp
 }
+
+define i1 @icmp_samesign_logical_and(i32 %In) {
+; CHECK-LABEL: @icmp_samesign_logical_and(
+; CHECK-NEXT:    [[C2:%.*]] = icmp eq i32 [[IN:%.*]], 1
+; CHECK-NEXT:    ret i1 [[C2]]
+;
+  %c1 = icmp samesign sgt i32 %In, -1
+  %c2 = icmp samesign eq i32 %In, 1
+  %V = select i1 %c1, i1 %c2, i1 false
+  ret i1 %V
+}

[elhewaty]

Oh, thank you very much for this.
Can you add a test for ne too? As the flag should be dropped there too.

[antoniofrighetto]

LGTM!

[nikic]

LGTM