[SelectionDAG] Add initial SimplifyDemandedVectorElts support for simplifying VSELECT...

This just adds a basic pass through - we can add constant selection mask handling in a future patch to fully match InstCombine.

llvm-svn: 325338

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index a066217ba17de51af5f8a913a1b3ee05b55228c1..8eef9b58c57d361720fcd0226c7348f695215e3e 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1411,6 +1411,26 @@ bool TargetLowering::SimplifyDemandedVectorElts(
     KnownZero.insertBits(SubZero, SubIdx);
     break;
   }
+  case ISD::VSELECT: {
+    APInt DemandedLHS(DemandedElts);
+    APInt DemandedRHS(DemandedElts);
+
+    // TODO - add support for constant vselect masks.
+
+    // See if we can simplify either vselect operand.
+    APInt UndefLHS, ZeroLHS;
+    APInt UndefRHS, ZeroRHS;
+    if (SimplifyDemandedVectorElts(Op.getOperand(1), DemandedLHS, UndefLHS,
+                                   ZeroLHS, TLO, Depth + 1))
+      return true;
+    if (SimplifyDemandedVectorElts(Op.getOperand(2), DemandedRHS, UndefRHS,
+                                   ZeroRHS, TLO, Depth + 1))
+      return true;
+
+    KnownUndef = UndefLHS & UndefRHS;
+    KnownZero = ZeroLHS & ZeroRHS;
+    break;
+  }
   case ISD::VECTOR_SHUFFLE: {
     ArrayRef<int> ShuffleMask = cast<ShuffleVectorSDNode>(Op)->getMask();
 

diff --git a/llvm/test/CodeGen/X86/known-bits-vector.ll b/llvm/test/CodeGen/X86/known-bits-vector.ll
index 46a888f3b9b6c09e6c016dc837e13079a8b940a0..9c1346d1be7cf566f9034f5b4f941069851ebd83 100644 (file)
--- a/llvm/test/CodeGen/X86/known-bits-vector.ll
+++ b/llvm/test/CodeGen/X86/known-bits-vector.ll
@@ -651,9 +651,7 @@ define <4 x float> @knownbits_lshr_and_select_shuffle_uitofp(<4 x i32> %a0, <4 x
 ; X32-NEXT:    andl $-16, %esp
 ; X32-NEXT:    subl $16, %esp
 ; X32-NEXT:    vmovaps 8(%ebp), %xmm3
-; X32-NEXT:    vpsrld $1, %xmm2, %xmm4
 ; X32-NEXT:    vpsrld $5, %xmm2, %xmm2
-; X32-NEXT:    vpblendw {{.*#+}} xmm2 = xmm2[0,1],xmm4[2,3],xmm2[4,5],xmm4[6,7]
 ; X32-NEXT:    vandps {{\.LCPI.*}}, %xmm3, %xmm3
 ; X32-NEXT:    vpcmpeqd %xmm1, %xmm0, %xmm0
 ; X32-NEXT:    vblendvps %xmm0, %xmm2, %xmm3, %xmm0
@@ -665,9 +663,7 @@ define <4 x float> @knownbits_lshr_and_select_shuffle_uitofp(<4 x i32> %a0, <4 x
 ;
 ; X64-LABEL: knownbits_lshr_and_select_shuffle_uitofp:
 ; X64:       # %bb.0:
-; X64-NEXT:    vpsrld $1, %xmm2, %xmm4
 ; X64-NEXT:    vpsrld $5, %xmm2, %xmm2
-; X64-NEXT:    vpblendw {{.*#+}} xmm2 = xmm2[0,1],xmm4[2,3],xmm2[4,5],xmm4[6,7]
 ; X64-NEXT:    vandps {{.*}}(%rip), %xmm3, %xmm3
 ; X64-NEXT:    vpcmpeqd %xmm1, %xmm0, %xmm0
 ; X64-NEXT:    vblendvps %xmm0, %xmm2, %xmm3, %xmm0