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author | Chris Lattner <sabre@nondot.org> | 2010-12-13 08:39:01 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2010-12-13 08:39:01 +0000 |
commit | de1c3605a649239cf8a96ba31885c8fbef2bc838 (patch) | |
tree | 4b2933b6d4e162daba87f508642c62d0d6ed4d10 /lib/CodeGen/SelectionDAG/DAGCombiner.cpp | |
parent | a9f6bbea62f42ab052eca423588e309ab67c3fa3 (diff) | |
download | external_llvm-de1c3605a649239cf8a96ba31885c8fbef2bc838.zip external_llvm-de1c3605a649239cf8a96ba31885c8fbef2bc838.tar.gz external_llvm-de1c3605a649239cf8a96ba31885c8fbef2bc838.tar.bz2 |
Add a couple dag combines to transform mulhi/mullo into a wider multiply
when the wider type is legal. This allows us to compile:
define zeroext i16 @test1(i16 zeroext %x) nounwind {
entry:
%div = udiv i16 %x, 33
ret i16 %div
}
into:
test1: # @test1
movzwl 4(%esp), %eax
imull $63551, %eax, %eax # imm = 0xF83F
shrl $21, %eax
ret
instead of:
test1: # @test1
movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F
mulw 4(%esp)
andl $65504, %edx # imm = 0xFFE0
movl %edx, %eax
shrl $5, %eax
ret
Implementing rdar://8760399 and example #4 from:
http://blog.regehr.org/archives/320
We should implement the same thing for [su]mul_hilo, but I don't
have immediate plans to do this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121696 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
-rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 0d3b0df..740b29b 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -1916,6 +1916,7 @@ SDValue DAGCombiner::visitMULHS(SDNode *N) { SDValue N1 = N->getOperand(1); ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1); EVT VT = N->getValueType(0); + DebugLoc DL = N->getDebugLoc(); // fold (mulhs x, 0) -> 0 if (N1C && N1C->isNullValue()) @@ -1929,6 +1930,22 @@ SDValue DAGCombiner::visitMULHS(SDNode *N) { if (N0.getOpcode() == ISD::UNDEF || N1.getOpcode() == ISD::UNDEF) return DAG.getConstant(0, VT); + // If the type twice as wide is legal, transform the mulhs to a wider multiply + // plus a shift. + if (VT.isSimple() && !VT.isVector()) { + MVT Simple = VT.getSimpleVT(); + unsigned SimpleSize = Simple.getSizeInBits(); + EVT NewVT = EVT::getIntegerVT(*DAG.getContext(), SimpleSize*2); + if (TLI.isOperationLegal(ISD::MUL, NewVT)) { + N0 = DAG.getNode(ISD::SIGN_EXTEND, DL, NewVT, N0); + N1 = DAG.getNode(ISD::SIGN_EXTEND, DL, NewVT, N1); + N1 = DAG.getNode(ISD::MUL, DL, NewVT, N0, N1); + N1 = DAG.getNode(ISD::SRA, DL, NewVT, N1, + DAG.getConstant(SimpleSize, getShiftAmountTy())); + return DAG.getNode(ISD::TRUNCATE, DL, VT, N1); + } + } + return SDValue(); } @@ -1937,6 +1954,7 @@ SDValue DAGCombiner::visitMULHU(SDNode *N) { SDValue N1 = N->getOperand(1); ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1); EVT VT = N->getValueType(0); + DebugLoc DL = N->getDebugLoc(); // fold (mulhu x, 0) -> 0 if (N1C && N1C->isNullValue()) @@ -1948,6 +1966,22 @@ SDValue DAGCombiner::visitMULHU(SDNode *N) { if (N0.getOpcode() == ISD::UNDEF || N1.getOpcode() == ISD::UNDEF) return DAG.getConstant(0, VT); + // If the type twice as wide is legal, transform the mulhu to a wider multiply + // plus a shift. + if (VT.isSimple() && !VT.isVector()) { + MVT Simple = VT.getSimpleVT(); + unsigned SimpleSize = Simple.getSizeInBits(); + EVT NewVT = EVT::getIntegerVT(*DAG.getContext(), SimpleSize*2); + if (TLI.isOperationLegal(ISD::MUL, NewVT)) { + N0 = DAG.getNode(ISD::ZERO_EXTEND, DL, NewVT, N0); + N1 = DAG.getNode(ISD::ZERO_EXTEND, DL, NewVT, N1); + N1 = DAG.getNode(ISD::MUL, DL, NewVT, N0, N1); + N1 = DAG.getNode(ISD::SRL, DL, NewVT, N1, + DAG.getConstant(SimpleSize, getShiftAmountTy())); + return DAG.getNode(ISD::TRUNCATE, DL, VT, N1); + } + } + return SDValue(); } @@ -2011,6 +2045,7 @@ SDValue DAGCombiner::visitSMUL_LOHI(SDNode *N) { SDValue Res = SimplifyNodeWithTwoResults(N, ISD::MUL, ISD::MULHS); if (Res.getNode()) return Res; + // TODO: Transform smul_lohi to mul if the wider mul is legal! return SDValue(); } @@ -2018,6 +2053,7 @@ SDValue DAGCombiner::visitUMUL_LOHI(SDNode *N) { SDValue Res = SimplifyNodeWithTwoResults(N, ISD::MUL, ISD::MULHU); if (Res.getNode()) return Res; + // TODO: Transform umul_lohi to mul if the wider mul is legal! return SDValue(); } |