X86 address mode isel tweak. If the base of the address is also used by a CopyToReg (i.e. it's likely live-out), do not fold the sub-expressions into the addressing mode to avoid computing the address twice. The CopyToReg use will be isel'ed to a LEA, re-use it for address instead.
This is not yet enabled. llvm-svn: 68082
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@ -41,6 +41,9 @@
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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using namespace llvm;
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#include "llvm/Support/CommandLine.h"
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static cl::opt<bool> AvoidDupAddrCompute("x86-avoid-dup-address", cl::Hidden);
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STATISTIC(NumLoadMoved, "Number of loads moved below TokenFactor");
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STATISTIC(NumLoadMoved, "Number of loads moved below TokenFactor");
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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@ -1035,7 +1038,28 @@ bool X86DAGToDAGISel::SelectAddr(SDValue Op, SDValue N, SDValue &Base,
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SDValue &Scale, SDValue &Index,
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SDValue &Scale, SDValue &Index,
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SDValue &Disp) {
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SDValue &Disp) {
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X86ISelAddressMode AM;
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X86ISelAddressMode AM;
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if (MatchAddress(N, AM))
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bool Done = false;
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if (AvoidDupAddrCompute && !N.hasOneUse()) {
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unsigned Opcode = N.getOpcode();
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if (Opcode != ISD::Constant && Opcode != ISD::FrameIndex &&
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Opcode != X86ISD::Wrapper) {
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// If we are able to fold N into addressing mode, then we'll allow it even
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// if N has multiple uses. In general, addressing computation is used as
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// addresses by all of its uses. But watch out for CopyToReg uses, that
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// means the address computation is liveout. It will be computed by a LEA
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// so we want to avoid computing the address twice.
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for (SDNode::use_iterator UI = N.getNode()->use_begin(),
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UE = N.getNode()->use_end(); UI != UE; ++UI) {
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if (UI->getOpcode() == ISD::CopyToReg) {
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MatchAddressBase(N, AM, true, 0);
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Done = true;
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break;
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}
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}
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}
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}
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if (!Done && MatchAddress(N, AM))
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return false;
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return false;
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MVT VT = N.getValueType();
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MVT VT = N.getValueType();
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