[DAG] visitTRUNCATE - attempt to truncate USUBSAT

Fold trunc(usubsat(zext(x),y)) -> usubsat(x,trunc(umin(y,satlimit)))

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 38efa53..be8fd03 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -12176,6 +12176,20 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
         return DAG.getNode(N0.getOpcode(), DL, VT, NarrowL, NarrowR);
       }
     }
+    break;
+  case ISD::USUBSAT:
+    // Truncate the USUBSAT only if LHS is a known zero-extension, its not
+    // enough to know that the upper bits are zero we must ensure that we don't
+    // introduce an extra truncate.
+    if (!LegalOperations && N0.hasOneUse() &&
+        N0.getOperand(0).getOpcode() == ISD::ZERO_EXTEND &&
+        N0.getOperand(0).getOperand(0).getScalarValueSizeInBits() <=
+            VT.getScalarSizeInBits() &&
+        hasOperation(N0.getOpcode(), VT)) {
+      return getTruncatedUSUBSAT(VT, SrcVT, N0.getOperand(0), N0.getOperand(1),
+                                 DAG, SDLoc(N));
+    }
+    break;
   }
 
   return SDValue();

diff --git a/llvm/test/CodeGen/X86/combine-sub-usat.ll b/llvm/test/CodeGen/X86/combine-sub-usat.ll
index 2ca2fc3..5e66fed 100644 (file)
--- a/llvm/test/CodeGen/X86/combine-sub-usat.ll
+++ b/llvm/test/CodeGen/X86/combine-sub-usat.ll
@@ -171,85 +171,65 @@ define <8 x i8> @combine_trunc_v8i16_v8i8(<8 x i8> %a0, <8 x i16> %a1) {
 define <8 x i16> @combine_trunc_v8i32_v8i16(<8 x i16> %a0, <8 x i32> %a1) {
 ; SSE2-LABEL: combine_trunc_v8i32_v8i16:
 ; SSE2:       # %bb.0:
-; SSE2-NEXT:    pxor %xmm4, %xmm4
-; SSE2-NEXT:    movdqa %xmm0, %xmm3
-; SSE2-NEXT:    punpckhwd {{.*#+}} xmm3 = xmm3[4],xmm4[4],xmm3[5],xmm4[5],xmm3[6],xmm4[6],xmm3[7],xmm4[7]
-; SSE2-NEXT:    punpcklwd {{.*#+}} xmm0 = xmm0[0],xmm4[0],xmm0[1],xmm4[1],xmm0[2],xmm4[2],xmm0[3],xmm4[3]
-; SSE2-NEXT:    movdqa {{.*#+}} xmm4 = [2147483648,2147483648,2147483648,2147483648]
-; SSE2-NEXT:    movdqa %xmm0, %xmm5
-; SSE2-NEXT:    psubd %xmm1, %xmm0
-; SSE2-NEXT:    pxor %xmm4, %xmm1
+; SSE2-NEXT:    movdqa {{.*#+}} xmm3 = [2147483648,2147483648,2147483648,2147483648]
+; SSE2-NEXT:    movdqa %xmm2, %xmm4
+; SSE2-NEXT:    pxor %xmm3, %xmm4
+; SSE2-NEXT:    movdqa {{.*#+}} xmm5 = [2147549183,2147549183,2147549183,2147549183]
+; SSE2-NEXT:    movdqa %xmm5, %xmm6
+; SSE2-NEXT:    pcmpgtd %xmm4, %xmm6
+; SSE2-NEXT:    pcmpeqd %xmm4, %xmm4
+; SSE2-NEXT:    pand %xmm6, %xmm2
+; SSE2-NEXT:    pxor %xmm4, %xmm6
+; SSE2-NEXT:    por %xmm2, %xmm6
+; SSE2-NEXT:    pslld $16, %xmm6
+; SSE2-NEXT:    psrad $16, %xmm6
+; SSE2-NEXT:    pxor %xmm1, %xmm3
+; SSE2-NEXT:    pcmpgtd %xmm3, %xmm5
+; SSE2-NEXT:    pxor %xmm5, %xmm4
+; SSE2-NEXT:    pand %xmm1, %xmm5
 ; SSE2-NEXT:    por %xmm4, %xmm5
-; SSE2-NEXT:    pcmpgtd %xmm1, %xmm5
-; SSE2-NEXT:    pand %xmm5, %xmm0
-; SSE2-NEXT:    movdqa %xmm2, %xmm1
-; SSE2-NEXT:    pxor %xmm4, %xmm1
-; SSE2-NEXT:    por %xmm3, %xmm4
-; SSE2-NEXT:    pcmpgtd %xmm1, %xmm4
-; SSE2-NEXT:    psubd %xmm2, %xmm3
-; SSE2-NEXT:    pand %xmm4, %xmm3
-; SSE2-NEXT:    pslld $16, %xmm3
-; SSE2-NEXT:    psrad $16, %xmm3
-; SSE2-NEXT:    pslld $16, %xmm0
-; SSE2-NEXT:    psrad $16, %xmm0
-; SSE2-NEXT:    packssdw %xmm3, %xmm0
+; SSE2-NEXT:    pslld $16, %xmm5
+; SSE2-NEXT:    psrad $16, %xmm5
+; SSE2-NEXT:    packssdw %xmm6, %xmm5
+; SSE2-NEXT:    psubusw %xmm5, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; SSE41-LABEL: combine_trunc_v8i32_v8i16:
 ; SSE41:       # %bb.0:
-; SSE41-NEXT:    pxor %xmm4, %xmm4
-; SSE41-NEXT:    pmovzxwd {{.*#+}} xmm3 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero
-; SSE41-NEXT:    punpckhwd {{.*#+}} xmm0 = xmm0[4],xmm4[4],xmm0[5],xmm4[5],xmm0[6],xmm4[6],xmm0[7],xmm4[7]
-; SSE41-NEXT:    pmaxud %xmm1, %xmm3
-; SSE41-NEXT:    psubd %xmm1, %xmm3
-; SSE41-NEXT:    pmaxud %xmm2, %xmm0
-; SSE41-NEXT:    psubd %xmm2, %xmm0
-; SSE41-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0],xmm4[1],xmm0[2],xmm4[3],xmm0[4],xmm4[5],xmm0[6],xmm4[7]
-; SSE41-NEXT:    pblendw {{.*#+}} xmm3 = xmm3[0],xmm4[1],xmm3[2],xmm4[3],xmm3[4],xmm4[5],xmm3[6],xmm4[7]
-; SSE41-NEXT:    packusdw %xmm0, %xmm3
-; SSE41-NEXT:    movdqa %xmm3, %xmm0
+; SSE41-NEXT:    movdqa {{.*#+}} xmm3 = [65535,65535,65535,65535]
+; SSE41-NEXT:    pminud %xmm3, %xmm2
+; SSE41-NEXT:    pminud %xmm3, %xmm1
+; SSE41-NEXT:    packusdw %xmm2, %xmm1
+; SSE41-NEXT:    psubusw %xmm1, %xmm0
 ; SSE41-NEXT:    retq
 ;
 ; SSE42-LABEL: combine_trunc_v8i32_v8i16:
 ; SSE42:       # %bb.0:
-; SSE42-NEXT:    pxor %xmm4, %xmm4
-; SSE42-NEXT:    pmovzxwd {{.*#+}} xmm3 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero
-; SSE42-NEXT:    punpckhwd {{.*#+}} xmm0 = xmm0[4],xmm4[4],xmm0[5],xmm4[5],xmm0[6],xmm4[6],xmm0[7],xmm4[7]
-; SSE42-NEXT:    pmaxud %xmm1, %xmm3
-; SSE42-NEXT:    psubd %xmm1, %xmm3
-; SSE42-NEXT:    pmaxud %xmm2, %xmm0
-; SSE42-NEXT:    psubd %xmm2, %xmm0
-; SSE42-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0],xmm4[1],xmm0[2],xmm4[3],xmm0[4],xmm4[5],xmm0[6],xmm4[7]
-; SSE42-NEXT:    pblendw {{.*#+}} xmm3 = xmm3[0],xmm4[1],xmm3[2],xmm4[3],xmm3[4],xmm4[5],xmm3[6],xmm4[7]
-; SSE42-NEXT:    packusdw %xmm0, %xmm3
-; SSE42-NEXT:    movdqa %xmm3, %xmm0
+; SSE42-NEXT:    movdqa {{.*#+}} xmm3 = [65535,65535,65535,65535]
+; SSE42-NEXT:    pminud %xmm3, %xmm2
+; SSE42-NEXT:    pminud %xmm3, %xmm1
+; SSE42-NEXT:    packusdw %xmm2, %xmm1
+; SSE42-NEXT:    psubusw %xmm1, %xmm0
 ; SSE42-NEXT:    retq
 ;
 ; AVX1-LABEL: combine_trunc_v8i32_v8i16:
 ; AVX1:       # %bb.0:
-; AVX1-NEXT:    vpxor %xmm2, %xmm2, %xmm2
-; AVX1-NEXT:    vpunpckhwd {{.*#+}} xmm2 = xmm0[4],xmm2[4],xmm0[5],xmm2[5],xmm0[6],xmm2[6],xmm0[7],xmm2[7]
-; AVX1-NEXT:    vpmovzxwd {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero
-; AVX1-NEXT:    vpmaxud %xmm1, %xmm0, %xmm0
-; AVX1-NEXT:    vpsubd %xmm1, %xmm0, %xmm0
-; AVX1-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; AVX1-NEXT:    vpmaxud %xmm1, %xmm2, %xmm2
-; AVX1-NEXT:    vpsubd %xmm1, %xmm2, %xmm1
-; AVX1-NEXT:    vmovdqa {{.*#+}} xmm2 = <0,1,4,5,8,9,12,13,u,u,u,u,u,u,u,u>
-; AVX1-NEXT:    vpshufb %xmm2, %xmm1, %xmm1
-; AVX1-NEXT:    vpshufb %xmm2, %xmm0, %xmm0
-; AVX1-NEXT:    vpunpcklqdq {{.*#+}} xmm0 = xmm0[0],xmm1[0]
+; AVX1-NEXT:    vextractf128 $1, %ymm1, %xmm2
+; AVX1-NEXT:    vmovdqa {{.*#+}} xmm3 = [65535,65535,65535,65535]
+; AVX1-NEXT:    vpminud %xmm3, %xmm2, %xmm2
+; AVX1-NEXT:    vpminud %xmm3, %xmm1, %xmm1
+; AVX1-NEXT:    vpackusdw %xmm2, %xmm1, %xmm1
+; AVX1-NEXT:    vpsubusw %xmm1, %xmm0, %xmm0
 ; AVX1-NEXT:    vzeroupper
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-LABEL: combine_trunc_v8i32_v8i16:
 ; AVX2:       # %bb.0:
-; AVX2-NEXT:    vpmovzxwd {{.*#+}} ymm0 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero,xmm0[4],zero,xmm0[5],zero,xmm0[6],zero,xmm0[7],zero
-; AVX2-NEXT:    vpmaxud %ymm1, %ymm0, %ymm0
-; AVX2-NEXT:    vpsubd %ymm1, %ymm0, %ymm0
-; AVX2-NEXT:    vpshufb {{.*#+}} ymm0 = ymm0[0,1,4,5,8,9,12,13,u,u,u,u,u,u,u,u,16,17,20,21,24,25,28,29,u,u,u,u,u,u,u,u]
-; AVX2-NEXT:    vpermq {{.*#+}} ymm0 = ymm0[0,2,2,3]
-; AVX2-NEXT:    # kill: def $xmm0 killed $xmm0 killed $ymm0
+; AVX2-NEXT:    vpbroadcastd {{.*#+}} ymm2 = [65535,65535,65535,65535,65535,65535,65535,65535]
+; AVX2-NEXT:    vpminud %ymm2, %ymm1, %ymm1
+; AVX2-NEXT:    vextracti128 $1, %ymm1, %xmm2
+; AVX2-NEXT:    vpackusdw %xmm2, %xmm1, %xmm1
+; AVX2-NEXT:    vpsubusw %xmm1, %xmm0, %xmm0
 ; AVX2-NEXT:    vzeroupper
 ; AVX2-NEXT:    retq
 ;