[X86] SimplifyDemandedBits - only narrow a broadcast source if we only have one use.

Helps with the regression noted on D109065 - don't truncate a broadcast source if the source has multiple uses.

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 3187c41..3520bbf 100644 (file)
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -40381,7 +40381,8 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
     // Don't attempt this on AVX512 as it might affect broadcast folding.
     // TODO: Should we attempt this for i32/i16 splats? They tend to be slower.
     if ((BitWidth == 64) && SrcVT.isScalarInteger() && !Subtarget.hasAVX512() &&
-        OriginalDemandedBits.countLeadingZeros() >= (BitWidth / 2)) {
+        OriginalDemandedBits.countLeadingZeros() >= (BitWidth / 2) &&
+        Src->hasOneUse()) {
       MVT NewSrcVT = MVT::getIntegerVT(BitWidth / 2);
       SDValue NewSrc =
           TLO.DAG.getNode(ISD::TRUNCATE, SDLoc(Src), NewSrcVT, Src);

diff --git a/llvm/test/CodeGen/X86/oddshuffles.ll b/llvm/test/CodeGen/X86/oddshuffles.ll
index 0a3ddb8..b7f7321 100644 (file)
--- a/llvm/test/CodeGen/X86/oddshuffles.ll
+++ b/llvm/test/CodeGen/X86/oddshuffles.ll
@@ -2261,13 +2261,10 @@ define <16 x i32> @splat_v3i32(<3 x i32>* %ptr) {
 ;
 ; AVX1-LABEL: splat_v3i32:
 ; AVX1:       # %bb.0:
-; AVX1-NEXT:    movq (%rdi), %rax
-; AVX1-NEXT:    vmovq %rax, %xmm0
-; AVX1-NEXT:    vxorps %xmm1, %xmm1, %xmm1
-; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2,3,4,5,6,7]
-; AVX1-NEXT:    vmovd %eax, %xmm2
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm2 = xmm2[0,0,0,0]
-; AVX1-NEXT:    vblendps {{.*#+}} ymm1 = ymm1[0,1],ymm2[2],ymm1[3,4,5,6,7]
+; AVX1-NEXT:    vmovddup {{.*#+}} xmm1 = mem[0,0]
+; AVX1-NEXT:    vxorps %xmm2, %xmm2, %xmm2
+; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm2[0],ymm1[1],ymm2[2,3,4,5,6,7]
+; AVX1-NEXT:    vblendps {{.*#+}} ymm1 = ymm2[0,1],ymm1[2],ymm2[3,4,5,6,7]
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-SLOW-LABEL: splat_v3i32:
@@ -2289,13 +2286,10 @@ define <16 x i32> @splat_v3i32(<3 x i32>* %ptr) {
 ;
 ; XOP-LABEL: splat_v3i32:
 ; XOP:       # %bb.0:
-; XOP-NEXT:    movq (%rdi), %rax
-; XOP-NEXT:    vmovq %rax, %xmm0
-; XOP-NEXT:    vxorps %xmm1, %xmm1, %xmm1
-; XOP-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2,3,4,5,6,7]
-; XOP-NEXT:    vmovd %eax, %xmm2
-; XOP-NEXT:    vpshufd {{.*#+}} xmm2 = xmm2[0,0,0,0]
-; XOP-NEXT:    vblendps {{.*#+}} ymm1 = ymm1[0,1],ymm2[2],ymm1[3,4,5,6,7]
+; XOP-NEXT:    vmovddup {{.*#+}} xmm1 = mem[0,0]
+; XOP-NEXT:    vxorps %xmm2, %xmm2, %xmm2
+; XOP-NEXT:    vblendps {{.*#+}} ymm0 = ymm2[0],ymm1[1],ymm2[2,3,4,5,6,7]
+; XOP-NEXT:    vblendps {{.*#+}} ymm1 = ymm2[0,1],ymm1[2],ymm2[3,4,5,6,7]
 ; XOP-NEXT:    retq
   %1 = load <3 x i32>, <3 x i32>* %ptr, align 1
   %2 = shufflevector <3 x i32> %1, <3 x i32> undef, <16 x i32> <i32 0, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>