[SelectionDAG] Fix isKnownNeverZeroFloat for vectors (#78308)

Return true iff all of vector elements are constant AND not zero

Fixes #77805

Previously, it'd return `true` (as in - the value is known to be never
zero) for any build_vector/splat_vector with non-constant elements.

Author: danilaml

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -5233,22 +5233,8 @@ bool SelectionDAG::isKnownNeverZeroFloat(SDValue Op) const {
          "Floating point type expected");
 
   // If the value is a constant, we can obviously see if it is a zero or not.
-  if (const ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Op))
-    return !C->isZero();
-
-  // Return false if we find any zero in a vector.
-  if (Op->getOpcode() == ISD::BUILD_VECTOR ||
-      Op->getOpcode() == ISD::SPLAT_VECTOR) {
-    for (const SDValue &OpVal : Op->op_values()) {
-      if (OpVal.isUndef())
-        return false;
-      if (auto *C = dyn_cast<ConstantFPSDNode>(OpVal))
-        if (C->isZero())
-          return false;
-    }
-    return true;
-  }
-  return false;
+  return ISD::matchUnaryFpPredicate(
+      Op, [](ConstantFPSDNode *C) { return !C->isZero(); });
 }
 
 bool SelectionDAG::isKnownNeverZero(SDValue Op, unsigned Depth) const {

llvm/test/CodeGen/X86/fminimum-fmaximum.ll

@@ -1328,36 +1328,51 @@ define <4 x float> @test_fmaximum_v4f32_splat(<4 x float> %x, float %y) {
 ; SSE2-LABEL: test_fmaximum_v4f32_splat:
 ; SSE2:       # %bb.0:
 ; SSE2-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,0,0,0]
-; SSE2-NEXT:    movaps %xmm0, %xmm2
+; SSE2-NEXT:    pxor %xmm2, %xmm2
+; SSE2-NEXT:    pcmpgtd %xmm0, %xmm2
+; SSE2-NEXT:    movdqa %xmm2, %xmm3
+; SSE2-NEXT:    pandn %xmm0, %xmm3
+; SSE2-NEXT:    movaps %xmm1, %xmm4
+; SSE2-NEXT:    andps %xmm2, %xmm4
+; SSE2-NEXT:    orps %xmm3, %xmm4
+; SSE2-NEXT:    pand %xmm2, %xmm0
+; SSE2-NEXT:    andnps %xmm1, %xmm2
+; SSE2-NEXT:    por %xmm2, %xmm0
+; SSE2-NEXT:    movdqa %xmm0, %xmm1
+; SSE2-NEXT:    maxps %xmm4, %xmm1
+; SSE2-NEXT:    movdqa %xmm0, %xmm2
 ; SSE2-NEXT:    cmpunordps %xmm0, %xmm2
-; SSE2-NEXT:    movaps %xmm0, %xmm3
-; SSE2-NEXT:    andps %xmm2, %xmm3
-; SSE2-NEXT:    maxps %xmm1, %xmm0
-; SSE2-NEXT:    andnps %xmm0, %xmm2
-; SSE2-NEXT:    orps %xmm3, %xmm2
-; SSE2-NEXT:    movaps %xmm2, %xmm0
+; SSE2-NEXT:    andps %xmm2, %xmm0
+; SSE2-NEXT:    andnps %xmm1, %xmm2
+; SSE2-NEXT:    orps %xmm2, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; AVX1-LABEL: test_fmaximum_v4f32_splat:
 ; AVX1:       # %bb.0:
 ; AVX1-NEXT:    vshufps {{.*#+}} xmm1 = xmm1[0,0,0,0]
-; AVX1-NEXT:    vmaxps %xmm1, %xmm0, %xmm1
+; AVX1-NEXT:    vblendvps %xmm0, %xmm1, %xmm0, %xmm2
+; AVX1-NEXT:    vblendvps %xmm0, %xmm0, %xmm1, %xmm0
+; AVX1-NEXT:    vmaxps %xmm2, %xmm0, %xmm1
 ; AVX1-NEXT:    vcmpunordps %xmm0, %xmm0, %xmm2
 ; AVX1-NEXT:    vblendvps %xmm2, %xmm0, %xmm1, %xmm0
 ; AVX1-NEXT:    retq
 ;
 ; AVX512-LABEL: test_fmaximum_v4f32_splat:
 ; AVX512:       # %bb.0:
 ; AVX512-NEXT:    vbroadcastss %xmm1, %xmm1
-; AVX512-NEXT:    vmaxps %xmm1, %xmm0, %xmm1
+; AVX512-NEXT:    vblendvps %xmm0, %xmm1, %xmm0, %xmm2
+; AVX512-NEXT:    vblendvps %xmm0, %xmm0, %xmm1, %xmm0
+; AVX512-NEXT:    vmaxps %xmm2, %xmm0, %xmm1
 ; AVX512-NEXT:    vcmpunordps %xmm0, %xmm0, %xmm2
 ; AVX512-NEXT:    vblendvps %xmm2, %xmm0, %xmm1, %xmm0
 ; AVX512-NEXT:    retq
 ;
 ; X86-LABEL: test_fmaximum_v4f32_splat:
 ; X86:       # %bb.0:
 ; X86-NEXT:    vbroadcastss {{[0-9]+}}(%esp), %xmm1
-; X86-NEXT:    vmaxps %xmm1, %xmm0, %xmm1
+; X86-NEXT:    vblendvps %xmm0, %xmm1, %xmm0, %xmm2
+; X86-NEXT:    vblendvps %xmm0, %xmm0, %xmm1, %xmm0
+; X86-NEXT:    vmaxps %xmm2, %xmm0, %xmm1
 ; X86-NEXT:    vcmpunordps %xmm0, %xmm0, %xmm2
 ; X86-NEXT:    vblendvps %xmm2, %xmm0, %xmm1, %xmm0
 ; X86-NEXT:    retl