[DAGCombiner] Add general constant vector support to (srl (shl x, c), c) -> (and x, cst2)

RKSimon · RKSimon · commit 618d3aedaf3d · 2016-10-20T11:10:21.000Z
We already supported scalar constant / splatted constant vector - now accepts any (non opaque) constant scalar / vector

llvm-svn: 284717
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4920,14 +4920,14 @@ SDValue DAGCombiner::visitSRL(SDNode *N) {
   }
 
   // fold (srl (shl x, c), c) -> (and x, cst2)
-  if (N1C && N0.getOpcode() == ISD::SHL && N0.getOperand(1) == N1) {
-    unsigned BitSize = N0.getScalarValueSizeInBits();
-    if (BitSize <= 64) {
-      uint64_t ShAmt = N1C->getZExtValue() + 64 - BitSize;
-      SDLoc DL(N);
-      return DAG.getNode(ISD::AND, DL, VT, N0.getOperand(0),
-                         DAG.getConstant(~0ULL >> ShAmt, DL, VT));
-    }
+  if (N0.getOpcode() == ISD::SHL && N0.getOperand(1) == N1 &&
+      isConstantOrConstantVector(N1, /* NoOpaques */ true)) {
+    SDLoc DL(N);
+    APInt AllBits = APInt::getAllOnesValue(N0.getScalarValueSizeInBits());
+    SDValue Mask =
+        DAG.getNode(ISD::SRL, DL, VT, DAG.getConstant(AllBits, DL, VT), N1);
+    AddToWorklist(Mask.getNode());
+    return DAG.getNode(ISD::AND, DL, VT, N0.getOperand(0), Mask);
   }
 
   // fold (srl (anyextend x), c) -> (and (anyextend (srl x, c)), mask)
diff --git a/llvm/test/CodeGen/X86/combine-srl.ll b/llvm/test/CodeGen/X86/combine-srl.ll
@@ -374,24 +374,12 @@ define <4 x i32> @combine_vec_lshr_shl_mask0(<4 x i32> %x) {
 define <4 x i32> @combine_vec_lshr_shl_mask1(<4 x i32> %x) {
 ; SSE-LABEL: combine_vec_lshr_shl_mask1:
 ; SSE:       # BB#0:
-; SSE-NEXT:    pmulld {{.*}}(%rip), %xmm0
-; SSE-NEXT:    movdqa %xmm0, %xmm1
-; SSE-NEXT:    psrld $5, %xmm1
-; SSE-NEXT:    movdqa %xmm0, %xmm2
-; SSE-NEXT:    psrld $3, %xmm2
-; SSE-NEXT:    pblendw {{.*#+}} xmm2 = xmm2[0,1,2,3],xmm1[4,5,6,7]
-; SSE-NEXT:    movdqa %xmm0, %xmm1
-; SSE-NEXT:    psrld $4, %xmm1
-; SSE-NEXT:    psrld $2, %xmm0
-; SSE-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0,1,2,3],xmm1[4,5,6,7]
-; SSE-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0,1],xmm2[2,3],xmm0[4,5],xmm2[6,7]
+; SSE-NEXT:    andps {{.*}}(%rip), %xmm0
 ; SSE-NEXT:    retq
 ;
 ; AVX-LABEL: combine_vec_lshr_shl_mask1:
 ; AVX:       # BB#0:
-; AVX-NEXT:    vmovdqa {{.*#+}} xmm1 = [2,3,4,5]
-; AVX-NEXT:    vpsllvd %xmm1, %xmm0, %xmm0
-; AVX-NEXT:    vpsrlvd %xmm1, %xmm0, %xmm0
+; AVX-NEXT:    vandps {{.*}}(%rip), %xmm0, %xmm0
 ; AVX-NEXT:    retq
   %1 =  shl <4 x i32> %x, <i32 2, i32 3, i32 4, i32 5>
   %2 = lshr <4 x i32> %1, <i32 2, i32 3, i32 4, i32 5>
