[X86] Disable commuting for the first source operand of zero masked scalar fma intrinsic instructions.

I believe this is the correct fix for D75506 rather than disabling all commuting. We can still commute the remaining two sources.

Differential Revision:m https://reviews.llvm.org/D75526

Author: topperc

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -1883,7 +1883,7 @@ X86InstrInfo::findThreeSrcCommutedOpIndices(const MachineInstr &MI,
   unsigned KMaskOp = -1U;
   if (X86II::isKMasked(TSFlags)) {
     // For k-zero-masked operations it is Ok to commute the first vector
-    // operand.
+    // operand. Unless this is an intrinsic instruction.
     // For regular k-masked operations a conservative choice is done as the
     // elements of the first vector operand, for which the corresponding bit
     // in the k-mask operand is set to 0, are copied to the result of the
@@ -1902,7 +1902,7 @@ X86InstrInfo::findThreeSrcCommutedOpIndices(const MachineInstr &MI,
 
     // The operand with index = 1 is used as a source for those elements for
     // which the corresponding bit in the k-mask is set to 0.
-    if (X86II::isKMergeMasked(TSFlags))
+    if (X86II::isKMergeMasked(TSFlags) || IsIntrinsic)
       FirstCommutableVecOp = 3;
 
     LastCommutableVecOp++;

llvm/test/CodeGen/X86/avx512-intrinsics.ll

@@ -5818,6 +5818,35 @@ define <4 x float>@test_int_x86_avx512_maskz_vfmadd_ss(<4 x float> %x0, <4 x flo
   ret <4 x float> %res2
 }
 
+; Make sure we don't commute this to fold the load as that source isn't commutable.
+define <4 x float> @test_int_x86_avx512_maskz_vfmadd_ss_load0(i8 zeroext %0, <4 x float>* nocapture readonly %1, float %2, float %3) {
+; X64-LABEL: test_int_x86_avx512_maskz_vfmadd_ss_load0:
+; X64:       # %bb.0:
+; X64-NEXT:    vmovaps (%rsi), %xmm2
+; X64-NEXT:    kmovw %edi, %k1
+; X64-NEXT:    vfmadd213ss {{.*#+}} xmm2 = (xmm0 * xmm2) + xmm1
+; X64-NEXT:    vmovaps %xmm2, %xmm0
+; X64-NEXT:    retq
+;
+; X86-LABEL: test_int_x86_avx512_maskz_vfmadd_ss_load0:
+; X86:       # %bb.0:
+; X86-NEXT:    vmovss {{.*#+}} xmm1 = mem[0],zero,zero,zero
+; X86-NEXT:    movb {{[0-9]+}}(%esp), %al
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT:    vmovaps (%ecx), %xmm0
+; X86-NEXT:    kmovw %eax, %k1
+; X86-NEXT:    vfmadd132ss {{.*#+}} xmm0 = (xmm0 * mem) + xmm1
+; X86-NEXT:    retl
+  %5 = load <4 x float>, <4 x float>* %1, align 16
+  %6 = extractelement <4 x float> %5, i64 0
+  %7 = tail call float @llvm.fma.f32(float %6, float %2, float %3) #2
+  %8 = bitcast i8 %0 to <8 x i1>
+  %9 = extractelement <8 x i1> %8, i64 0
+  %10 = select i1 %9, float %7, float 0.000000e+00
+  %11 = insertelement <4 x float> %5, float %10, i64 0
+  ret <4 x float> %11
+}
+
 define <2 x double>@test_int_x86_avx512_mask3_vfmadd_sd(<2 x double> %x0, <2 x double> %x1, <2 x double> %x2, i8 %x3,i32 %x4 ){
 ; X64-LABEL: test_int_x86_avx512_mask3_vfmadd_sd:
 ; X64:       # %bb.0: