[llvm] simplifyBinaryIntrinsic: Return nan if snan is passed maxnum/minnum (PR #158470)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: YunQiang Su (wzssyqa)

<details>
<summary>Changes</summary>

Fixes: #<!-- -->138303

---
Full diff: https://github.com/llvm/llvm-project/pull/158470.diff


3 Files Affected:

- (modified) llvm/include/llvm/IR/PatternMatch.h (+4) 
- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+9-4) 
- (modified) llvm/test/Transforms/EarlyCSE/commute.ll (+33) 


``````````diff
diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index 2cb78904dd799..10cf451091198 100644
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -707,9 +707,13 @@ m_SpecificInt_ICMP(ICmpInst::Predicate Predicate, const APInt &Threshold) {
 struct is_nan {
   bool isValue(const APFloat &C) const { return C.isNaN(); }
 };
+struct is_snan {
+  bool isValue(const APFloat &C) const { return C.isSignaling(); }
+};
 /// Match an arbitrary NaN constant. This includes quiet and signalling nans.
 /// For vectors, this includes constants with undefined elements.
 inline cstfp_pred_ty<is_nan> m_NaN() { return cstfp_pred_ty<is_nan>(); }
+inline cstfp_pred_ty<is_snan> m_SNaN() { return cstfp_pred_ty<is_snan>(); }
 
 struct is_nonnan {
   bool isValue(const APFloat &C) const { return !C.isNaN(); }
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 7bff13d59528c..cff8f6dfe8117 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -6735,12 +6735,17 @@ Value *llvm::simplifyBinaryIntrinsic(Intrinsic::ID IID, Type *ReturnType,
     bool PropagateNaN = IID == Intrinsic::minimum || IID == Intrinsic::maximum;
     bool IsMin = IID == Intrinsic::minimum || IID == Intrinsic::minnum;
 
-    // minnum(X, nan) -> X
-    // maxnum(X, nan) -> X
+    // minnum(X, qnan) -> X
+    // maxnum(X, qnan) -> X
+    // minnum(X, snan) -> nan
+    // maxnum(X, snan) -> nan
     // minimum(X, nan) -> nan
     // maximum(X, nan) -> nan
-    if (match(Op1, m_NaN()))
-      return PropagateNaN ? propagateNaN(cast<Constant>(Op1)) : Op0;
+    if (match(Op1, m_NaN())) {
+      if (PropagateNaN || match(Op1, m_SNaN()))
+        return propagateNaN(cast<Constant>(Op1));
+      return Op0;
+    }
 
     // In the following folds, inf can be replaced with the largest finite
     // float, if the ninf flag is set.
diff --git a/llvm/test/Transforms/EarlyCSE/commute.ll b/llvm/test/Transforms/EarlyCSE/commute.ll
index edafeccd3c8cc..3e1f9abb8bd99 100644
--- a/llvm/test/Transforms/EarlyCSE/commute.ll
+++ b/llvm/test/Transforms/EarlyCSE/commute.ll
@@ -830,6 +830,39 @@ define float @maxnum(float %a, float %b) {
   ret float %r
 }
 
+define float @maxnum_const_snan(float %x) {
+; CHECK-LABEL: @maxnum_const_snan(
+; CHECK-NEXT:    ret float 0x7FFC000000000000
+;
+  %r = call float @llvm.minnum.f32(float %x, float 0x7FF4000000000000)
+  ret float %r
+}
+
+define double @minnum_const_snan(double %x) {
+; CHECK-LABEL: @minnum_const_snan(
+; CHECK-NEXT:    ret double 0x7FFC000000000000
+;
+  %r = call double @llvm.minnum.f64(double %x, double 0x7FF4000000000000)
+  ret double %r
+}
+
+define float @maxnum_const_qnan(float %x) {
+; CHECK-LABEL: @maxnum_const_qnan(
+; CHECK-NEXT:    ret float [[X:%.*]]
+;
+  %r = call float @llvm.minnum.f32(float %x, float 0x7FF8000000000000)
+  ret float %r
+}
+
+define double @minnum_const_qnan(double %x) {
+; CHECK-LABEL: @minnum_const_qnan(
+; CHECK-NEXT:    ret double [[X:%.*]]
+;
+  %r = call double @llvm.minnum.f64(double %x, double 0x7FF8000000000000)
+  ret double %r
+}
+
+
 define <2 x float> @minnum(<2 x float> %a, <2 x float> %b) {
 ; CHECK-LABEL: @minnum(
 ; CHECK-NEXT:    [[X:%.*]] = call fast <2 x float> @llvm.minnum.v2f32(<2 x float> [[A:%.*]], <2 x float> [[B:%.*]])

``````````

</details>


https://github.com/llvm/llvm-project/pull/158470