[llvm] PatternMatch: Add matchers for positive or negative infinity (PR #188933)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

The existing m_Inf deceptively matches both positive and negative
infinities. Add variants that match the specific sign.

---
Full diff: https://github.com/llvm/llvm-project/pull/188933.diff


2 Files Affected:

- (modified) llvm/include/llvm/IR/PatternMatch.h (+18) 
- (modified) llvm/unittests/IR/PatternMatch.cpp (+6) 


``````````diff
diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index 94ae65a24b3e2..2160146245137 100644
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -763,6 +763,24 @@ struct is_inf {
 /// For vectors, this includes constants with undefined elements.
 inline cstfp_pred_ty<is_inf> m_Inf() { return cstfp_pred_ty<is_inf>(); }
 
+template <bool IsNegative> struct is_signed_inf {
+  bool isValue(const APFloat &C) const {
+    return C.isInfinity() && IsNegative == C.isNegative();
+  }
+};
+
+/// Match a positive infinity FP constant.
+/// For vectors, this includes constants with undefined elements.
+inline cstfp_pred_ty<is_signed_inf<false>> m_PosInf() {
+  return cstfp_pred_ty<is_signed_inf<false>>();
+}
+
+/// Match a negative infinity FP constant.
+/// For vectors, this includes constants with undefined elements.
+inline cstfp_pred_ty<is_signed_inf<true>> m_NegInf() {
+  return cstfp_pred_ty<is_signed_inf<true>>();
+}
+
 struct is_noninf {
   bool isValue(const APFloat &C) const { return !C.isInfinity(); }
 };
diff --git a/llvm/unittests/IR/PatternMatch.cpp b/llvm/unittests/IR/PatternMatch.cpp
index 8a4385b62ab72..8cbec2cba8392 100644
--- a/llvm/unittests/IR/PatternMatch.cpp
+++ b/llvm/unittests/IR/PatternMatch.cpp
@@ -1755,6 +1755,12 @@ TEST_F(PatternMatchTest, VectorUndefFloat) {
   EXPECT_TRUE(match(VectorInfPoison, m_Inf()));
   EXPECT_FALSE(match(VectorNaNPoison, m_Inf()));
 
+  EXPECT_TRUE(match(ScalarPosInf, m_PosInf()));
+  EXPECT_FALSE(match(ScalarNegInf, m_PosInf()));
+
+  EXPECT_FALSE(match(ScalarPosInf, m_NegInf()));
+  EXPECT_TRUE(match(ScalarNegInf, m_NegInf()));
+
   EXPECT_FALSE(match(ScalarUndef, m_NonInf()));
   EXPECT_FALSE(match(VectorUndef, m_NonInf()));
   EXPECT_FALSE(match(VectorZeroUndef, m_NonInf()));

``````````

</details>


https://github.com/llvm/llvm-project/pull/188933