[SelectionDAG] Add SIGN_EXTEND_VECTOR_INREG and CONCAT_VECTORS support to SimplifyDemandedBits

Fix for AVX1 masked load/store regression on D52964

llvm-svn: 344043

2 files changed, 30 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 1c3c60b1a85..2858f4cdfae 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -573,6 +573,17 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
       Known.Zero &= Known2.Zero;
     }
     return false;   // Don't fall through, will infinitely loop.
+  case ISD::CONCAT_VECTORS:
+    Known.Zero.setAllBits();
+    Known.One.setAllBits();
+    for (SDValue SrcOp : Op->ops()) {
+      if (SimplifyDemandedBits(SrcOp, NewMask, Known2, TLO, Depth + 1))
+        return true;
+      // Known bits are the values that are shared by every subvector.
+      Known.One &= Known2.One;
+      Known.Zero &= Known2.Zero;
+    }
+    break;
   case ISD::AND:
     // If the RHS is a constant, check to see if the LHS would be zero without
     // using the bits from the RHS.  Below, we use knowledge about the RHS to
@@ -1104,6 +1115,25 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
                                                Op.getOperand(0)));
     break;
   }
+  case ISD::SIGN_EXTEND_VECTOR_INREG: {
+    // TODO - merge this with SIGN_EXTEND above?
+    SDValue Src = Op.getOperand(0);
+    unsigned InBits = Src.getValueType().getScalarSizeInBits();
+
+    APInt InDemandedBits = NewMask.trunc(InBits);
+
+    // If some of the sign extended bits are demanded, we know that the sign
+    // bit is demanded.
+    if (InBits < NewMask.getActiveBits())
+      InDemandedBits.setBit(InBits - 1);
+
+    if (SimplifyDemandedBits(Src, InDemandedBits, Known, TLO, Depth + 1))
+      return true;
+    assert(!Known.hasConflict() && "Bits known to be one AND zero?");
+    // If the sign bit is known one, the top bits match.
+    Known = Known.sext(BitWidth);
+    break;
+  }
   case ISD::ANY_EXTEND: {
     unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits();
     APInt InMask = NewMask.trunc(OperandBitWidth);
diff --git a/llvm/test/CodeGen/X86/vselect-avx.ll b/llvm/test/CodeGen/X86/vselect-avx.ll
index e03b6fff313..e27493e9758 100644
--- a/llvm/test/CodeGen/X86/vselect-avx.ll
+++ b/llvm/test/CodeGen/X86/vselect-avx.ll
@@ -41,7 +41,6 @@ define void @test2(double** %call1559, i64 %indvars.iv4198, <4 x i1> %tmp1895) {
 ; AVX1-LABEL: test2:
 ; AVX1:       ## %bb.0: ## %bb
 ; AVX1-NEXT:    vpslld $31, %xmm0, %xmm0
-; AVX1-NEXT:    vpsrad $31, %xmm0, %xmm0
 ; AVX1-NEXT:    vpmovsxdq %xmm0, %xmm1
 ; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[2,3,0,1]
 ; AVX1-NEXT:    vpmovsxdq %xmm0, %xmm0