[InstCombine] use canIgnoreSignBitOfZero in spf->minmax fold

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -3929,7 +3929,10 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
 
     // Canonicalize select of FP values where NaN and -0.0 are not valid as
     // minnum/maxnum intrinsics.
-    if (SIFPOp->hasNoNaNs() && SIFPOp->hasNoSignedZeros()) {
+    if (SIFPOp->hasNoNaNs() &&
+        (SIFPOp->hasNoSignedZeros() ||
+         (SIFPOp->hasOneUse() &&
+          canIgnoreSignBitOfZero(*SIFPOp->use_begin())))) {
       Value *X, *Y;
       if (match(&SI, m_OrdOrUnordFMax(m_Value(X), m_Value(Y)))) {
         Value *BinIntr =

llvm/test/Transforms/InstCombine/minmax-fp.ll

@@ -174,8 +174,7 @@ define i8 @t11(float %a, float %b) {
 ; Either operand could be NaN, but nnan modifier applied.
 define i8 @t12(float %a, float %b) {
 ; CHECK-LABEL: @t12(
-; CHECK-NEXT:    [[DOTINV:%.*]] = fcmp nnan oge float [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[DOTV:%.*]] = select nnan i1 [[DOTINV]], float [[A]], float [[B]]
+; CHECK-NEXT:    [[DOTV:%.*]] = call nnan float @llvm.minnum.f32(float [[B:%.*]], float [[A:%.*]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = fptosi float [[DOTV]] to i8
 ; CHECK-NEXT:    ret i8 [[TMP1]]
 ;