[llvm] r226816 - [DAGCombine] Produce better code for constant splats
Michael Kuperstein
michael.m.kuperstein at intel.com
Thu Jan 22 05:07:29 PST 2015
Author: mkuper
Date: Thu Jan 22 07:07:28 2015
New Revision: 226816
URL: http://llvm.org/viewvc/llvm-project?rev=226816&view=rev
Log:
[DAGCombine] Produce better code for constant splats
This solves PR22276.
Splats of constants would sometimes produce redundant shuffles, sometimes ridiculously so (see the PR for details). Fold these shuffles into BUILD_VECTORs early on instead.
Differential Revision: http://reviews.llvm.org/D7093
Fixed recommit of r226811.
Added:
llvm/trunk/test/CodeGen/X86/splat-const.ll
- copied unchanged from r226813, llvm/trunk/test/CodeGen/X86/splat-const.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
llvm/trunk/test/CodeGen/X86/sse41.ll
llvm/trunk/test/CodeGen/X86/widen_shuffle-1.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=226816&r1=226815&r2=226816&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Jan 22 07:07:28 2015
@@ -11490,7 +11490,7 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE
}
// If it is a splat, check if the argument vector is another splat or a
- // build_vector with all scalar elements the same.
+ // build_vector.
if (SVN->isSplat() && SVN->getSplatIndex() < (int)NumElts) {
SDNode *V = N0.getNode();
@@ -11527,6 +11527,24 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE
// Splat of <x, x, x, x>, return <x, x, x, x>
if (AllSame)
return N0;
+
+ // If the splatted element is a constant, just build the vector out of
+ // constants directly.
+ const SDValue &Splatted = V->getOperand(SVN->getSplatIndex());
+ if (isa<ConstantSDNode>(Splatted) || isa<ConstantFPSDNode>(Splatted)) {
+ SmallVector<SDValue, 8> Ops;
+ for (unsigned i = 0; i != NumElts; ++i) {
+ Ops.push_back(Splatted);
+ }
+ SDValue NewBV = DAG.getNode(ISD::BUILD_VECTOR, SDLoc(N),
+ V->getValueType(0), Ops);
+
+ // We may have jumped through bitcasts, so the type of the
+ // BUILD_VECTOR may not match the type of the shuffle.
+ if (V->getValueType(0) != VT)
+ NewBV = DAG.getNode(ISD::BITCAST, SDLoc(N), VT, NewBV);
+ return NewBV;
+ }
}
}
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=226816&r1=226815&r2=226816&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Thu Jan 22 07:07:28 2015
@@ -1513,9 +1513,10 @@ SDValue SelectionDAG::getVectorShuffle(E
return getUNDEF(VT);
// If Identity shuffle return that node.
- bool Identity = true;
+ bool Identity = true, AllSame = true;
for (unsigned i = 0; i != NElts; ++i) {
if (MaskVec[i] >= 0 && MaskVec[i] != (int)i) Identity = false;
+ if (MaskVec[i] != MaskVec[0]) AllSame = false;
}
if (Identity && NElts)
return N1;
@@ -1549,6 +1550,26 @@ SDValue SelectionDAG::getVectorShuffle(E
if (C->isNullValue())
return N1;
}
+
+ // If the shuffle itself creates a constant splat, build the vector
+ // directly.
+ if (AllSame) {
+ const SDValue &Splatted = BV->getOperand(MaskVec[0]);
+ if (isa<ConstantSDNode>(Splatted) || isa<ConstantFPSDNode>(Splatted)) {
+ SmallVector<SDValue, 8> Ops;
+ for (unsigned i = 0; i != NElts; ++i) {
+ Ops.push_back(Splatted);
+ }
+ SDValue NewBV = getNode(ISD::BUILD_VECTOR, dl,
+ BV->getValueType(0), Ops);
+
+ // We may have jumped through bitcasts, so the type of the
+ // BUILD_VECTOR may not match the type of the shuffle.
+ if (BV->getValueType(0) != VT)
+ NewBV = getNode(ISD::BITCAST, dl, VT, NewBV);
+ return NewBV;
+ }
+ }
}
}
Modified: llvm/trunk/test/CodeGen/X86/sse41.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/sse41.ll?rev=226816&r1=226815&r2=226816&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/sse41.ll (original)
+++ llvm/trunk/test/CodeGen/X86/sse41.ll Thu Jan 22 07:07:28 2015
@@ -1003,14 +1003,14 @@ define void @insertps_pr20411(i32* noali
; X32-LABEL: insertps_pr20411:
; X32: ## BB#0:
; X32-NEXT: movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT: pshufd {{.*#+}} xmm0 = mem[3,1,2,3]
+; X32-NEXT: movaps {{.*#+}} xmm0 = [3,3,3,3]
; X32-NEXT: insertps $-36, LCPI49_1+12, %xmm0
; X32-NEXT: movups %xmm0, (%eax)
; X32-NEXT: retl
;
; X64-LABEL: insertps_pr20411:
; X64: ## BB#0:
-; X64-NEXT: pshufd {{.*#+}} xmm0 = mem[3,1,2,3]
+; X64-NEXT: movaps {{.*#+}} xmm0 = [3,3,3,3]
; X64-NEXT: insertps $-36, LCPI49_1+{{.*}}(%rip), %xmm0
; X64-NEXT: movups %xmm0, (%rdi)
; X64-NEXT: retq
Modified: llvm/trunk/test/CodeGen/X86/widen_shuffle-1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/widen_shuffle-1.ll?rev=226816&r1=226815&r2=226816&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/widen_shuffle-1.ll (original)
+++ llvm/trunk/test/CodeGen/X86/widen_shuffle-1.ll Thu Jan 22 07:07:28 2015
@@ -82,8 +82,8 @@ define void @shuf5(<8 x i8>* %p) nounwin
; CHECK-LABEL: shuf5:
; CHECK: # BB#0:
; CHECK-NEXT: movl {{[0-9]+}}(%esp), %eax
-; CHECK-NEXT: movdqa {{.*#+}} xmm0 = <4,33,u,u,u,u,u,u>
-; CHECK-NEXT: pshufb {{.*#+}} xmm0 = xmm0[2,2,4,6,8,10,12,14,u,u,u,u,u,u,u,u]
+; CHECK-NEXT: movdqa {{.*#+}} xmm0 = [33,33,33,33,33,33,33,33]
+; CHECK-NEXT: pshufb {{.*#+}} xmm0 = xmm0[0,2,4,6,8,10,12,14,u,u,u,u,u,u,u,u]
; CHECK-NEXT: movlpd %xmm0, (%eax)
; CHECK-NEXT: retl
%v = shufflevector <2 x i8> <i8 4, i8 33>, <2 x i8> undef, <8 x i32> <i32 1, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
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