[X86][FP16] Fix mis-combination from FMULC to FCMULC

[pengfei]

Summary

The combination was designed to combine a negative imaginary value
rather then a full negative complex value.

[pengfei]

ping

[RKSimon]

LGTM

llvm/lib/Target/X86/X86ISelLowering.cpp

         return CI->getValue() == ConjugationInt32;
       case 64:
         return CI->getValue() == ConjugationInt64;
       default:
         llvm_unreachable("Unexpected bit width");
       }
     }
     if (const auto *CF = dyn_cast<ConstantFP>(c))
-      return CF->isNegativeZeroValue();
+      return CF->getType()->isFloatTy() && CF->isNegativeZeroValue();
     return false;
   };
   auto combineConjugation = [&](SDValue &r) {
     if (LHS->getOpcode() == ISD::BITCAST && RHS.hasOneUse()) {
       SDValue XOR = LHS.getOperand(0);
       if (XOR->getOpcode() == ISD::XOR && XOR.hasOneUse()) {
         SDValue XORRHS = XOR.getOperand(1);
         if (XORRHS.getOpcode() == ISD::BITCAST && XORRHS.hasOneUse())

llvm/test/CodeGen/X86/avx512fp16-combine-xor-vfmulc.ll

entry:
   %3 = tail call fast <4 x float> @llvm.x86.avx512fp16.mask.vfcmul.cph.128(<4 x float> %1, <4 x float> %2, <4 x float> zeroinitializer, i8 -1) #2
   %4 = bitcast <4 x float> %3 to <8 x half>
   ret <8 x half> %4
 }
 
 define dso_local <32 x half> @test5(<32 x half> noundef %a, <32 x half> noundef %b) local_unnamed_addr #0 {
 ; CHECK-LABEL: test5:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    vfcmulcph %zmm1, %zmm0, %zmm2
-; CHECK-NEXT:    vmovaps %zmm2, %zmm0
+; CHECK-NEXT:    vpbroadcastw {{.*#+}} zmm2 = [-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0,-0.0E+0]
+; CHECK-NEXT:    vpxorq %zmm2, %zmm1, %zmm2
+; CHECK-NEXT:    vfmulcph %zmm2, %zmm0, %zmm1
+; CHECK-NEXT:    vmovaps %zmm1, %zmm0
 ; CHECK-NEXT:    retq
 entry:
   %fneg = fneg <32 x half> %b
   %0 = bitcast <32 x half> %a to <16 x float>
   %1 = bitcast <32 x half> %fneg to <16 x float>
   %2 = tail call <16 x float> @llvm.x86.avx512fp16.mask.vfmul.cph.512(<16 x float> %0, <16 x float> %1, <16 x float> zeroinitializer, i16 -1, i32 4)
   %3 = bitcast <16 x float> %2 to <32 x half>
   ret <32 x half> %3
 }
 
 declare <16 x float> @llvm.x86.avx512fp16.mask.vfmul.cph.512(<16 x float>, <16 x float>, <16 x float>, i16, i32 immarg)
 declare <8 x float> @llvm.x86.avx512fp16.mask.vfmul.cph.256(<8 x float>, <8 x float>, <8 x float>, i8)
 declare <4 x float> @llvm.x86.avx512fp16.mask.vfmul.cph.128(<4 x float>, <4 x float>, <4 x float>, i8)
 declare <4 x float> @llvm.x86.avx512fp16.mask.vfcmul.cph.128(<4 x float>, <4 x float>, <4 x float>, i8)