[X86][SSE] Sign extension for target vector sizes less than 128 bits.

[RKSimon]

Summary

To add support for v2i8/v2i16 to v2f64, this patch adds support for sign extension for sub 128-bit vectors, such as to v2i32 (which can then be converted to v2f64). It concatenates with UNDEF subvectors up to 128-bits, performs the sign extension (i.e. as v4i32) and then extracts the target subvector.

This is really 2 patches (the sign extension of subvectors + conversion of v2i8/v2i16 to v2f64) so I will commit these separately after combined review.

[RKSimon]

Minor fix + rebase.

[qcolombet]

Hi Simon,

LGTM.

Thanks,
-Quentin

[RKSimon]

Thanks Quentin. BTW, I'm still working on improving the vectorization costs mechanism - it's just taking a little longer than planned.

llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

static SDValue PerformSINT_TO_FPCombine(SDNode *N, SelectionDAG &DAG,
                                         const X86Subtarget *Subtarget) {
   // First try to optimize away the conversion entirely when it's
   // conditionally from a constant. Vectors only.
   if (SDValue Res = performVectorCompareAndMaskUnaryOpCombine(N, DAG))
     return Res;
 
   // Now move on to more general possibilities.
   SDValue Op0 = N->getOperand(0);
-  EVT InVT = Op0->getValueType(0);
+  EVT VT = N->getValueType(0);
+  EVT InVT = Op0.getValueType();
+  EVT InSVT = InVT.getScalarType();
 
   // SINT_TO_FP(vXi8) -> SINT_TO_FP(SEXT(vXi8 to vXi32))
   // SINT_TO_FP(vXi16) -> SINT_TO_FP(SEXT(vXi16 to vXi32))
-  if (InVT == MVT::v8i8 || InVT == MVT::v4i8 ||
-      InVT == MVT::v8i16 || InVT == MVT::v4i16) {
+  if (InVT.isVector() && (InSVT == MVT::i8 || InSVT == MVT::i16)) {
     SDLoc dl(N);
-    MVT DstVT = MVT::getVectorVT(MVT::i32, InVT.getVectorNumElements());
+    EVT DstVT = EVT::getVectorVT(*DAG.getContext(), MVT::i32,
+                                 InVT.getVectorNumElements());
     SDValue P = DAG.getNode(ISD::SIGN_EXTEND, dl, DstVT, Op0);
-    return DAG.getNode(ISD::SINT_TO_FP, dl, N->getValueType(0), P);
+    return DAG.getNode(ISD::SINT_TO_FP, dl, VT, P);
   }
 
   // Transform (SINT_TO_FP (i64 ...)) into an x87 operation if we have
   // a 32-bit target where SSE doesn't support i64->FP operations.
   if (Op0.getOpcode() == ISD::LOAD) {
     LoadSDNode *Ld = cast<LoadSDNode>(Op0.getNode());
     EVT LdVT = Ld->getValueType(0);
 
     // This transformation is not supported if the result type is f16
-    if (N->getValueType(0) == MVT::f16)
+    if (VT == MVT::f16)
       return SDValue();
 
-    if (!Ld->isVolatile() && !N->getValueType(0).isVector() &&
+    if (!Ld->isVolatile() && !VT.isVector() &&
         ISD::isNON_EXTLoad(Op0.getNode()) && Op0.hasOneUse() &&
         !Subtarget->is64Bit() && LdVT == MVT::i64) {
       SDValue FILDChain = Subtarget->getTargetLowering()->BuildFILD(
           SDValue(N, 0), LdVT, Ld->getChain(), Op0, DAG);
       DAG.ReplaceAllUsesOfValueWith(Op0.getValue(1), FILDChain.getValue(1));
       return FILDChain;
     }
   }

llvm/trunk/test/CodeGen/X86/vec_int_to_fp.ll

; AVX-NEXT:    retq
   %shuf = shufflevector <4 x i32> %a, <4 x i32> undef, <2 x i32> <i32 0, i32 1>
   %cvt = sitofp <2 x i32> %shuf to <2 x double>
   ret <2 x double> %cvt
 }
 
 define <2 x double> @sitofp_2vf64_i16(<8 x i16> %a) {
 ; SSE2-LABEL: sitofp_2vf64_i16:
 ; SSE2:       # BB#0:
-; SSE2-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[0,1,0,3]
-; SSE2-NEXT:    pshufhw {{.*#+}} xmm0 = xmm0[0,1,2,3,5,5,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
-; SSE2-NEXT:    movd %xmm1, %rax
-; SSE2-NEXT:    movswq %ax, %rax
-; SSE2-NEXT:    movd %xmm0, %rcx
-; SSE2-NEXT:    movswq %cx, %rcx
-; SSE2-NEXT:    xorps %xmm0, %xmm0
-; SSE2-NEXT:    cvtsi2sdq %rcx, %xmm0
-; SSE2-NEXT:    xorps %xmm1, %xmm1
-; SSE2-NEXT:    cvtsi2sdq %rax, %xmm1
-; SSE2-NEXT:    unpcklpd {{.*#+}} xmm0 = xmm0[0],xmm1[0]
+; SSE2-NEXT:    punpcklwd {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3]
+; SSE2-NEXT:    psrad $16, %xmm0
+; SSE2-NEXT:    cvtdq2pd %xmm0, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; AVX-LABEL: sitofp_2vf64_i16:
 ; AVX:       # BB#0:
-; AVX-NEXT:    vpmovzxwq {{.*#+}} xmm0 = xmm0[0],zero,zero,zero,xmm0[1],zero,zero,zero
-; AVX-NEXT:    vmovq %xmm0, %rax
-; AVX-NEXT:    movswq %ax, %rax
-; AVX-NEXT:    vpextrq $1, %xmm0, %rcx
-; AVX-NEXT:    movswq %cx, %rcx
-; AVX-NEXT:    vxorps %xmm0, %xmm0, %xmm0
-; AVX-NEXT:    vcvtsi2sdq %rcx, %xmm0, %xmm0
-; AVX-NEXT:    vcvtsi2sdq %rax, %xmm0, %xmm1
-; AVX-NEXT:    vunpcklpd {{.*#+}} xmm0 = xmm1[0],xmm0[0]
+; AVX-NEXT:    vpmovsxwd %xmm0, %xmm0
+; AVX-NEXT:    vcvtdq2pd %xmm0, %xmm0
 ; AVX-NEXT:    retq
   %shuf = shufflevector <8 x i16> %a, <8 x i16> undef, <2 x i32> <i32 0, i32 1>
   %cvt = sitofp <2 x i16> %shuf to <2 x double>
   ret <2 x double> %cvt
 }
 
 define <2 x double> @sitofp_2vf64_i8(<16 x i8> %a) {
 ; SSE2-LABEL: sitofp_2vf64_i8:
 ; SSE2:       # BB#0:
 ; SSE2-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
 ; SSE2-NEXT:    punpcklwd {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3]
-; SSE2-NEXT:    punpckldq {{.*#+}} xmm0 = xmm0[0,0,1,1]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
-; SSE2-NEXT:    movd %xmm1, %rax
-; SSE2-NEXT:    movsbq %al, %rax
-; SSE2-NEXT:    movd %xmm0, %rcx
-; SSE2-NEXT:    movsbq %cl, %rcx
-; SSE2-NEXT:    xorps %xmm0, %xmm0
-; SSE2-NEXT:    cvtsi2sdq %rcx, %xmm0
-; SSE2-NEXT:    xorps %xmm1, %xmm1
-; SSE2-NEXT:    cvtsi2sdq %rax, %xmm1
-; SSE2-NEXT:    unpcklpd {{.*#+}} xmm0 = xmm0[0],xmm1[0]
+; SSE2-NEXT:    psrad $24, %xmm0
+; SSE2-NEXT:    cvtdq2pd %xmm0, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; AVX-LABEL: sitofp_2vf64_i8:
 ; AVX:       # BB#0:
-; AVX-NEXT:    vpmovzxbq {{.*#+}} xmm0 = xmm0[0],zero,zero,zero,zero,zero,zero,zero,xmm0[1],zero,zero,zero,zero,zero,zero,zero
-; AVX-NEXT:    vmovq %xmm0, %rax
-; AVX-NEXT:    movsbq %al, %rax
-; AVX-NEXT:    vpextrq $1, %xmm0, %rcx
-; AVX-NEXT:    movsbq %cl, %rcx
-; AVX-NEXT:    vxorps %xmm0, %xmm0, %xmm0
-; AVX-NEXT:    vcvtsi2sdq %rcx, %xmm0, %xmm0
-; AVX-NEXT:    vcvtsi2sdq %rax, %xmm0, %xmm1
-; AVX-NEXT:    vunpcklpd {{.*#+}} xmm0 = xmm1[0],xmm0[0]
+; AVX-NEXT:    vpmovsxbd %xmm0, %xmm0
+; AVX-NEXT:    vcvtdq2pd %xmm0, %xmm0
 ; AVX-NEXT:    retq
   %shuf = shufflevector <16 x i8> %a, <16 x i8> undef, <2 x i32> <i32 0, i32 1>
   %cvt = sitofp <2 x i8> %shuf to <2 x double>
   ret <2 x double> %cvt
 }
 
 define <4 x double> @sitofp_4vf64(<4 x i64> %a) {
 ; SSE2-LABEL: sitofp_4vf64:

llvm/trunk/test/CodeGen/X86/widen_conv-3.ll

 ; RUN: llc < %s -march=x86 -mattr=+sse4.2 | FileCheck %s
-; CHECK: cvtsi2ss
+; CHECK: cvtdq2ps
 
 ; sign to float v2i16 to v2f32
 
 define void @convert(<2 x float>* %dst.addr, <2 x i16> %src) nounwind {
 entry:
   %val = sitofp <2 x i16> %src to <2 x float>
   store <2 x float> %val, <2 x float>* %dst.addr
   ret void
 }