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authorAdam Nemet <anemet@apple.com>2014-04-18 19:44:16 +0000
committerAdam Nemet <anemet@apple.com>2014-04-18 19:44:16 +0000
commitd290fa608fe090903f306c10d27a0e181fe6fb3b (patch)
tree0d6e0bb55db79ef042542587916798448223facf /lib
parent842c27189a7a6c698d10da84d483627da1da0c1d (diff)
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[X86] Improve buildFromShuffleMostly for AVX
For a 256-bit BUILD_VECTOR consisting mostly of shuffles of 256-bit vectors, both the BUILD_VECTOR and its operands may need to be legalized in multiple steps. Consider: (v8f32 (BUILD_VECTOR (extract_vector_elt (v8f32 %vreg0,) Constant<1>), (extract_vector_elt %vreg0, Constant<2>), (extract_vector_elt %vreg0, Constant<3>), (extract_vector_elt %vreg0, Constant<4>), (extract_vector_elt %vreg0, Constant<5>), (extract_vector_elt %vreg0, Constant<6>), (extract_vector_elt %vreg0, Constant<7>), %vreg1)) a. We can't build a 256-bit vector efficiently so, we need to split it into two 128-bit vecs and combine them with VINSERTX128. b. Operands like (extract_vector_elt (v8f32 %vreg0), Constant<7>) needs to be split into a VEXTRACTX128 and a further extract_vector_elt from the resulting 128-bit vector. c. The extract_vector_elt from b. is lowered into a shuffle to the first element and a movss. Depending on the order in which we legalize the BUILD_VECTOR and its operands[1], buildFromShuffleMostly may be faced with: (v4f32 (BUILD_VECTOR (extract_vector_elt (vector_shuffle<1,u,u,u> (extract_subvector %vreg0, Constant<4>), undef), Constant<0>), (extract_vector_elt (vector_shuffle<2,u,u,u> (extract_subvector %vreg0, Constant<4>), undef), Constant<0>), (extract_vector_elt (vector_shuffle<3,u,u,u> (extract_subvector %vreg0, Constant<4>), undef), Constant<0>), %vreg1)) In order to figure out the underlying vector and their identity we need to see through the shuffles. [1] Note that the order in which operations and their operands are legalized is only guaranteed in the first iteration of LegalizeDAG. Fixes <rdar://problem/16296956> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206634 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r--lib/Target/X86/X86ISelLowering.cpp45
1 files changed, 39 insertions, 6 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 815d27ff5e..306fb7e199 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5703,6 +5703,41 @@ static SDValue LowerVectorBroadcast(SDValue Op, const X86Subtarget* Subtarget,
return SDValue();
}
+/// \brief For an EXTRACT_VECTOR_ELT with a constant index return the real
+/// underlying vector and index.
+///
+/// Modifies \p ExtractedFromVec to the real vector and returns the real
+/// index.
+static int getUnderlyingExtractedFromVec(SDValue &ExtractedFromVec,
+ SDValue ExtIdx) {
+ int Idx = cast<ConstantSDNode>(ExtIdx)->getZExtValue();
+ if (!isa<ShuffleVectorSDNode>(ExtractedFromVec))
+ return Idx;
+
+ // For 256-bit vectors, LowerEXTRACT_VECTOR_ELT_SSE4 may have already
+ // lowered this:
+ // (extract_vector_elt (v8f32 %vreg1), Constant<6>)
+ // to:
+ // (extract_vector_elt (vector_shuffle<2,u,u,u>
+ // (extract_subvector (v8f32 %vreg0), Constant<4>),
+ // undef)
+ // Constant<0>)
+ // In this case the vector is the extract_subvector expression and the index
+ // is 2, as specified by the shuffle.
+ ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(ExtractedFromVec);
+ SDValue ShuffleVec = SVOp->getOperand(0);
+ MVT ShuffleVecVT = ShuffleVec.getSimpleValueType();
+ assert(ShuffleVecVT.getVectorElementType() ==
+ ExtractedFromVec.getSimpleValueType().getVectorElementType());
+
+ int ShuffleIdx = SVOp->getMaskElt(Idx);
+ if (isUndefOrInRange(ShuffleIdx, 0, ShuffleVecVT.getVectorNumElements())) {
+ ExtractedFromVec = ShuffleVec;
+ return ShuffleIdx;
+ }
+ return Idx;
+}
+
static SDValue buildFromShuffleMostly(SDValue Op, SelectionDAG &DAG) {
MVT VT = Op.getSimpleValueType();
@@ -5736,15 +5771,15 @@ static SDValue buildFromShuffleMostly(SDValue Op, SelectionDAG &DAG) {
SDValue ExtractedFromVec = Op.getOperand(i).getOperand(0);
SDValue ExtIdx = Op.getOperand(i).getOperand(1);
+ // Quit if non-constant index.
+ if (!isa<ConstantSDNode>(ExtIdx))
+ return SDValue();
+ int Idx = getUnderlyingExtractedFromVec(ExtractedFromVec, ExtIdx);
// Quit if extracted from vector of different type.
if (ExtractedFromVec.getValueType() != VT)
return SDValue();
- // Quit if non-constant index.
- if (!isa<ConstantSDNode>(ExtIdx))
- return SDValue();
-
if (VecIn1.getNode() == 0)
VecIn1 = ExtractedFromVec;
else if (VecIn1 != ExtractedFromVec) {
@@ -5755,8 +5790,6 @@ static SDValue buildFromShuffleMostly(SDValue Op, SelectionDAG &DAG) {
return SDValue();
}
- unsigned Idx = cast<ConstantSDNode>(ExtIdx)->getZExtValue();
-
if (ExtractedFromVec == VecIn1)
Mask[i] = Idx;
else if (ExtractedFromVec == VecIn2)