[X86][FP16] Fix vector_shuffle and lowering without f16c feature problems

The problem Alexander reported on D127982 was caused by an optimization
for AVX512-FP16 instruction. We must limit it to the feature enabled only.

During the investigation, I found we didn't expand for fp_round/fp_extend
without F16C. This may result runtime crash, so change them too.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D130817

(cherry picked from commit 23021d4)

Author: phoebewang

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -1362,6 +1362,8 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
 
     setOperationAction(ISD::SINT_TO_FP,         MVT::v8i32, Custom);
     setOperationAction(ISD::STRICT_SINT_TO_FP,  MVT::v8i32, Custom);
+    setOperationAction(ISD::FP_EXTEND,          MVT::v8f32, Expand);
+    setOperationAction(ISD::FP_ROUND,           MVT::v8f16, Expand);
     setOperationAction(ISD::FP_EXTEND,          MVT::v4f64, Custom);
     setOperationAction(ISD::STRICT_FP_EXTEND,   MVT::v4f64, Custom);
 
@@ -16120,16 +16122,18 @@ static SDValue lowerV8F16Shuffle(const SDLoc &DL, ArrayRef<int> Mask,
   assert(Mask.size() == 8 && "Unexpected mask size for v8 shuffle!");
   int NumV2Elements = count_if(Mask, [](int M) { return M >= 8; });
 
-  if (NumV2Elements == 0) {
-    // Check for being able to broadcast a single element.
-    if (SDValue Broadcast = lowerShuffleAsBroadcast(DL, MVT::v8f16, V1, V2,
-                                                    Mask, Subtarget, DAG))
-      return Broadcast;
+  if (Subtarget.hasFP16()) {
+    if (NumV2Elements == 0) {
+      // Check for being able to broadcast a single element.
+      if (SDValue Broadcast = lowerShuffleAsBroadcast(DL, MVT::v8f16, V1, V2,
+                                                      Mask, Subtarget, DAG))
+        return Broadcast;
+    }
+    if (NumV2Elements == 1 && Mask[0] >= 8)
+      if (SDValue V = lowerShuffleAsElementInsertion(
+              DL, MVT::v8f16, V1, V2, Mask, Zeroable, Subtarget, DAG))
+        return V;
   }
-  if (NumV2Elements == 1 && Mask[0] >= 8)
-    if (SDValue V = lowerShuffleAsElementInsertion(DL, MVT::v8f16, V1, V2, Mask,
-                                                   Zeroable, Subtarget, DAG))
-      return V;
 
   V1 = DAG.getBitcast(MVT::v8i16, V1);
   V2 = DAG.getBitcast(MVT::v8i16, V2);

llvm/test/CodeGen/X86/half.ll

@@ -1297,4 +1297,30 @@ define <8 x half> @select(i1 %c, <8 x half> %x, <8 x half> %y) {
   ret <8 x half> %s
 }
 
+define <8 x half> @shuffle(ptr %p) {
+; CHECK-LIBCALL-LABEL: shuffle:
+; CHECK-LIBCALL:       # %bb.0:
+; CHECK-LIBCALL-NEXT:    movdqu (%rdi), %xmm0
+; CHECK-LIBCALL-NEXT:    pshufhw {{.*#+}} xmm0 = xmm0[0,1,2,3,4,4,4,4]
+; CHECK-LIBCALL-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[2,2,2,2]
+; CHECK-LIBCALL-NEXT:    retq
+;
+; BWON-F16C-LABEL: shuffle:
+; BWON-F16C:       # %bb.0:
+; BWON-F16C-NEXT:    vpshufhw {{.*#+}} xmm0 = mem[0,1,2,3,4,4,4,4]
+; BWON-F16C-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[2,2,2,2]
+; BWON-F16C-NEXT:    retq
+;
+; CHECK-I686-LABEL: shuffle:
+; CHECK-I686:       # %bb.0:
+; CHECK-I686-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; CHECK-I686-NEXT:    movdqu (%eax), %xmm0
+; CHECK-I686-NEXT:    pshufhw {{.*#+}} xmm0 = xmm0[0,1,2,3,4,4,4,4]
+; CHECK-I686-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[2,2,2,2]
+; CHECK-I686-NEXT:    retl
+  %1 = load <8 x half>, ptr %p, align 8
+  %2 = shufflevector <8 x half> %1, <8 x half> poison, <8 x i32> <i32 4, i32 4, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+  ret <8 x half> %2
+}
+
 attributes #0 = { nounwind }