Lower vselects into X86ISD::BLENDI when appropriate.

LowerVSELECT will, if possible, generate a X86ISD::BLENDI DAG node if the
condition is constant and we can emit that instruction, given the
subtarget.

This is not enough for all cases. An additional SELECTCombine optimization
will be committed.

Fixed tests that were expecting variable blends but where a blend+imm can
be generated.
Added test where we can't emit blend+immediate.
Added avx2 blend+imm tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209043 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 860af12..c6e7730 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -7971,7 +7971,87 @@ X86TargetLowering::LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const {
   return SDValue();
 }
 
+// This function assumes its argument is a BUILD_VECTOR of constand or
+// undef SDNodes. i.e: ISD::isBuildVectorOfConstantSDNodes(BuildVector) is
+// true.
+static bool BUILD_VECTORtoBlendMask(BuildVectorSDNode *BuildVector,
+                                    unsigned &MaskValue) {
+  MaskValue = 0;
+  unsigned NumElems = BuildVector->getNumOperands();
+  // There are 2 lanes if (NumElems > 8), and 1 lane otherwise.
+  unsigned NumLanes = (NumElems - 1) / 8 + 1;
+  unsigned NumElemsInLane = NumElems / NumLanes;
+
+  // Blend for v16i16 should be symetric for the both lanes.
+  for (unsigned i = 0; i < NumElemsInLane; ++i) {
+    SDValue EltCond = BuildVector->getOperand(i);
+    SDValue SndLaneEltCond =
+        (NumLanes == 2) ? BuildVector->getOperand(i + NumElemsInLane) : EltCond;
+
+    int Lane1Cond = -1, Lane2Cond = -1;
+    if (isa<ConstantSDNode>(EltCond))
+      Lane1Cond = !isZero(EltCond);
+    if (isa<ConstantSDNode>(SndLaneEltCond))
+      Lane2Cond = !isZero(SndLaneEltCond);
+
+    if (Lane1Cond == Lane2Cond || Lane2Cond < 0)
+      MaskValue |= !!Lane1Cond << i;
+    else if (Lane1Cond < 0)
+      MaskValue |= !!Lane2Cond << i;
+    else
+      return false;
+  }
+  return true;
+}
+
+// Try to lower a vselect node into a simple blend instruction.
+static SDValue LowerVSELECTtoBlend(SDValue Op, const X86Subtarget *Subtarget,
+                                   SelectionDAG &DAG) {
+  SDValue Cond = Op.getOperand(0);
+  SDValue LHS = Op.getOperand(1);
+  SDValue RHS = Op.getOperand(2);
+  SDLoc dl(Op);
+  MVT VT = Op.getSimpleValueType();
+  MVT EltVT = VT.getVectorElementType();
+  unsigned NumElems = VT.getVectorNumElements();
+
+  // There is no blend with immediate in AVX-512.
+  if (VT.is512BitVector())
+    return SDValue();
+
+  if (!Subtarget->hasSSE41() || EltVT == MVT::i8)
+    return SDValue();
+  if (!Subtarget->hasInt256() && VT == MVT::v16i16)
+    return SDValue();
+
+  if (!ISD::isBuildVectorOfConstantSDNodes(Cond.getNode()))
+    return SDValue();
+
+  // Check the mask for BLEND and build the value.
+  unsigned MaskValue = 0;
+  if (!BUILD_VECTORtoBlendMask(cast<BuildVectorSDNode>(Cond), MaskValue))
+    return SDValue();
+
+  // Convert i32 vectors to floating point if it is not AVX2.
+  // AVX2 introduced VPBLENDD instruction for 128 and 256-bit vectors.
+  MVT BlendVT = VT;
+  if (EltVT == MVT::i64 || (EltVT == MVT::i32 && !Subtarget->hasInt256())) {
+    BlendVT = MVT::getVectorVT(MVT::getFloatingPointVT(EltVT.getSizeInBits()),
+                               NumElems);
+    LHS = DAG.getNode(ISD::BITCAST, dl, VT, LHS);
+    RHS = DAG.getNode(ISD::BITCAST, dl, VT, RHS);
+  }
+
+  SDValue Ret = DAG.getNode(X86ISD::BLENDI, dl, BlendVT, LHS, RHS,
+                            DAG.getConstant(MaskValue, MVT::i32));
+  return DAG.getNode(ISD::BITCAST, dl, VT, Ret);
+}
+
 SDValue X86TargetLowering::LowerVSELECT(SDValue Op, SelectionDAG &DAG) const {
+  SDValue BlendOp = LowerVSELECTtoBlend(Op, Subtarget, DAG);
+  if (BlendOp.getNode())
+    return BlendOp;
+
   // Some types for vselect were previously set to Expand, not Legal or
   // Custom. Return an empty SDValue so we fall-through to Expand, after
   // the Custom lowering phase.
@@ -7984,7 +8064,9 @@ SDValue X86TargetLowering::LowerVSELECT(SDValue Op, SelectionDAG &DAG) const {
     return SDValue();
   }
 
-  // This node is Legal.
+  // We couldn't create a "Blend with immediate" node.
+  // This node should still be legal, but we'll have to emit a blendv*
+  // instruction.
   return Op;
 }
 

diff --git a/test/CodeGen/X86/avx-blend.ll b/test/CodeGen/X86/avx-blend.ll
index 5fcd5ff..4757ce0 100644 (file)
--- a/test/CodeGen/X86/avx-blend.ll
+++ b/test/CodeGen/X86/avx-blend.ll
@@ -3,7 +3,7 @@
 ; AVX128 tests:
 
 ;CHECK-LABEL: vsel_float:
-;CHECK: vblendvps
+;CHECK: vblendps    $5
 ;CHECK: ret
 define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 false, i1 true, i1 false>, <4 x float> %v1, <4 x float> %v2
@@ -12,7 +12,7 @@ define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
 
 
 ;CHECK-LABEL: vsel_i32:
-;CHECK: vblendvps
+;CHECK: vblendps   $5
 ;CHECK: ret
 define <4 x i32> @vsel_i32(<4 x i32> %v1, <4 x i32> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 false, i1 true, i1 false>, <4 x i32> %v1, <4 x i32> %v2
@@ -52,7 +52,7 @@ define <16 x i8> @vsel_i8(<16 x i8> %v1, <16 x i8> %v2) {
 
 ;CHECK-LABEL: vsel_float8:
 ;CHECK-NOT: vinsertf128
-;CHECK: vblendvps
+;CHECK: vblendps    $17
 ;CHECK: ret
 define <8 x float> @vsel_float8(<8 x float> %v1, <8 x float> %v2) {
   %vsel = select <8 x i1> <i1 true, i1 false, i1 false, i1 false, i1 true, i1 false, i1 false, i1 false>, <8 x float> %v1, <8 x float> %v2
@@ -61,7 +61,7 @@ define <8 x float> @vsel_float8(<8 x float> %v1, <8 x float> %v2) {
 
 ;CHECK-LABEL: vsel_i328:
 ;CHECK-NOT: vinsertf128
-;CHECK: vblendvps
+;CHECK: vblendps    $17
 ;CHECK-NEXT: ret
 define <8 x i32> @vsel_i328(<8 x i32> %v1, <8 x i32> %v2) {
   %vsel = select <8 x i1> <i1 true, i1 false, i1 false, i1 false, i1 true, i1 false, i1 false, i1 false>, <8 x i32> %v1, <8 x i32> %v2
@@ -86,7 +86,7 @@ define <8 x i64> @vsel_i648(<8 x i64> %v1, <8 x i64> %v2) {
 
 ;CHECK-LABEL: vsel_double4:
 ;CHECK-NOT: vinsertf128
-;CHECK: vblendvpd
+;CHECK: vblendpd    $5
 ;CHECK-NEXT: ret
 define <4 x double> @vsel_double4(<4 x double> %v1, <4 x double> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 false, i1 true, i1 false>, <4 x double> %v1, <4 x double> %v2

diff --git a/test/CodeGen/X86/avx2.ll b/test/CodeGen/X86/avx2.ll
new file mode 100644 (file)
index 0000000..290d0b6
--- /dev/null
+++ b/test/CodeGen/X86/avx2.ll
@@ -0,0 +1,25 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=core-avx2 -mattr=+avx2 | FileCheck %s
+
+define <4 x i32> @blendvb_fallback_v4i32(<4 x i1> %mask, <4 x i32> %x, <4 x i32> %y) {
+; CHECK-LABEL: @blendvb_fallback_v4i32
+; CHECK: vblendvps
+; CHECK: ret
+  %ret = select <4 x i1> %mask, <4 x i32> %x, <4 x i32> %y
+  ret <4 x i32> %ret
+}
+
+define <8 x i32> @blendvb_fallback_v8i32(<8 x i1> %mask, <8 x i32> %x, <8 x i32> %y) {
+; CHECK-LABEL: @blendvb_fallback_v8i32
+; CHECK: vblendvps
+; CHECK: ret
+  %ret = select <8 x i1> %mask, <8 x i32> %x, <8 x i32> %y
+  ret <8 x i32> %ret
+}
+
+define <8 x float> @blendvb_fallback_v8f32(<8 x i1> %mask, <8 x float> %x, <8 x float> %y) {
+; CHECK-LABEL: @blendvb_fallback_v8f32
+; CHECK: vblendvps
+; CHECK: ret
+  %ret = select <8 x i1> %mask, <8 x float> %x, <8 x float> %y
+  ret <8 x float> %ret
+}

diff --git a/test/CodeGen/X86/blend-msb.ll b/test/CodeGen/X86/blend-msb.ll
index 6b46596..4e17a71 100644 (file)
--- a/test/CodeGen/X86/blend-msb.ll
+++ b/test/CodeGen/X86/blend-msb.ll
@@ -4,7 +4,7 @@
 ; Verify that we produce movss instead of blendvps when possible.
 
 ;CHECK-LABEL: vsel_float:
-;CHECK-NOT: blendvps
+;CHECK-NOT: blend
 ;CHECK: movss
 ;CHECK: ret
 define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
@@ -13,7 +13,7 @@ define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
 }
 
 ;CHECK-LABEL: vsel_4xi8:
-;CHECK-NOT: blendvps
+;CHECK-NOT: blend
 ;CHECK: movss
 ;CHECK: ret
 define <4 x i8> @vsel_4xi8(<4 x i8> %v1, <4 x i8> %v2) {
@@ -21,14 +21,8 @@ define <4 x i8> @vsel_4xi8(<4 x i8> %v1, <4 x i8> %v2) {
   ret <4 x i8> %vsel
 }
 
-
-; We do not have native support for v8i16 blends and we have to use the
-; blendvb instruction or a sequence of NAND/OR/AND. Make sure that we do not
-; reduce the mask in this case.
 ;CHECK-LABEL: vsel_8xi16:
-;CHECK: andps
-;CHECK: andps
-;CHECK: orps
+;CHECK: pblendw $17
 ;CHECK: ret
 define <8 x i16> @vsel_8xi16(<8 x i16> %v1, <8 x i16> %v2) {
   %vsel = select <8 x i1> <i1 true, i1 false, i1 false, i1 false, i1 true, i1 false, i1 false, i1 false>, <8 x i16> %v1, <8 x i16> %v2

diff --git a/test/CodeGen/X86/sse41-blend.ll b/test/CodeGen/X86/sse41-blend.ll
index 4681fde..951bb7d 100644 (file)
--- a/test/CodeGen/X86/sse41-blend.ll
+++ b/test/CodeGen/X86/sse41-blend.ll
@@ -1,7 +1,7 @@
 ; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=corei7 -mattr=+sse4.1 | FileCheck %s
 
 ;CHECK-LABEL: vsel_float:
-;CHECK: blendvps
+;CHECK: blendps
 ;CHECK: ret
 define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 false, i1 true, i1 true>, <4 x float> %v1, <4 x float> %v2
@@ -10,7 +10,7 @@ define <4 x float> @vsel_float(<4 x float> %v1, <4 x float> %v2) {
 
 
 ;CHECK-LABEL: vsel_4xi8:
-;CHECK: blendvps
+;CHECK: blendps
 ;CHECK: ret
 define <4 x i8> @vsel_4xi8(<4 x i8> %v1, <4 x i8> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 true, i1 false, i1 true>, <4 x i8> %v1, <4 x i8> %v2
@@ -18,7 +18,7 @@ define <4 x i8> @vsel_4xi8(<4 x i8> %v1, <4 x i8> %v2) {
 }
 
 ;CHECK-LABEL: vsel_4xi16:
-;CHECK: blendvps
+;CHECK: blendps
 ;CHECK: ret
 define <4 x i16> @vsel_4xi16(<4 x i16> %v1, <4 x i16> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 false, i1 true, i1 true>, <4 x i16> %v1, <4 x i16> %v2
@@ -27,7 +27,7 @@ define <4 x i16> @vsel_4xi16(<4 x i16> %v1, <4 x i16> %v2) {
 
 
 ;CHECK-LABEL: vsel_i32:
-;CHECK: blendvps
+;CHECK: blendps
 ;CHECK: ret
 define <4 x i32> @vsel_i32(<4 x i32> %v1, <4 x i32> %v2) {
   %vsel = select <4 x i1> <i1 true, i1 true, i1 false, i1 true>, <4 x i32> %v1, <4 x i32> %v2

diff --git a/test/CodeGen/X86/sse41.ll b/test/CodeGen/X86/sse41.ll
index db0d9c5..3652d8c 100644 (file)
--- a/test/CodeGen/X86/sse41.ll
+++ b/test/CodeGen/X86/sse41.ll
@@ -576,3 +576,11 @@ define < 4 x float> @test_insertps_no_undef(<4 x float> %x) {
   %res = select  <4 x i1> %mask, <4 x float> %x, <4 x float>%vecinit5
   ret <4 x float> %res
 }
+
+define <8 x i16> @blendvb_fallback(<8 x i1> %mask, <8 x i16> %x, <8 x i16> %y) {
+; CHECK-LABEL: blendvb_fallback
+; CHECK: blendvb
+; CHECK: ret
+  %ret = select <8 x i1> %mask, <8 x i16> %x, <8 x i16> %y
+  ret <8 x i16> %ret
+}