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If a copy isn't coalesced, but its src is defined by trivial computation. Re-materialize the src to replace the copy.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55467 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-08-28 07:53:51 +00:00
parent 66e13153bd
commit 9242cb8b82
4 changed files with 72 additions and 6 deletions
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65
lib/CodeGen/SimpleRegisterCoalescing.cpp
View File

@ -38,6 +38,7 @@ STATISTIC(numJoins , "Number of interval joins performed");
STATISTIC(numSubJoins , "Number of subclass joins performed");
STATISTIC(numCommutes , "Number of instruction commuting performed");
STATISTIC(numExtends , "Number of copies extended");
STATISTIC(NumReMats , "Number of instructions re-materialized");
STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
STATISTIC(numAborts , "Number of times interval joining aborted");
@ -426,6 +427,43 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
return true;
}
/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
/// computation, replace the copy by rematerialize the definition.
bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
unsigned DstReg,
MachineInstr *CopyMI) {
unsigned CopyIdx = li_->getUseIndex(li_->getInstructionIndex(CopyMI));
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
if (SrcLR == SrcInt.end()) // Should never happen!
return false;
VNInfo *ValNo = SrcLR->valno;
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (ValNo->def == ~0U || ValNo->def == ~1U || ValNo->hasPHIKill)
return false;
MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
const TargetInstrDesc &TID = DefMI->getDesc();
if (!TID.isAsCheapAsAMove())
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(tii_, SawStore))
return false;
unsigned DefIdx = li_->getDefIndex(CopyIdx);
const LiveRange *DLR= li_->getInterval(DstReg).getLiveRangeContaining(DefIdx);
DLR->valno->copy = NULL;
MachineBasicBlock::iterator MII = CopyMI;
MachineBasicBlock *MBB = CopyMI->getParent();
tii_->reMaterialize(*MBB, MII, DstReg, DefMI);
MachineInstr *NewMI = prior(MII);
li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
CopyMI->eraseFromParent();
ReMatCopies.insert(CopyMI);
++NumReMats;
return true;
}
/// isBackEdgeCopy - Returns true if CopyMI is a back edge copy.
///
bool SimpleRegisterCoalescing::isBackEdgeCopy(MachineInstr *CopyMI,
@ -475,6 +513,17 @@ SimpleRegisterCoalescing::UpdateRegDefsUses(unsigned SrcReg, unsigned DstReg,
unsigned UseDstReg = DstReg;
if (OldSubIdx)
UseDstReg = tri_->getSubReg(DstReg, OldSubIdx);
unsigned CopySrcReg, CopyDstReg;
if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg) &&
CopySrcReg != CopyDstReg &&
CopySrcReg == SrcReg && CopyDstReg != UseDstReg) {
// If the use is a copy and it won't be coalesced away, and its source
// is defined by a trivial computation, try to rematerialize it instead.
if (ReMaterializeTrivialDef(li_->getInterval(SrcReg), CopyDstReg,UseMI))
continue;
}
O.setReg(UseDstReg);
O.setSubReg(0);
} else {
@ -865,7 +914,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
MachineInstr *CopyMI = TheCopy.MI;
Again = false;
if (JoinedCopies.count(CopyMI))
if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
return false; // Already done.
DOUT << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI;
@ -1108,6 +1157,12 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
if (!isEmpty && !JoinIntervals(DstInt, SrcInt, Swapped)) {
// Coalescing failed.
// If definition of source is defined by trivial computation, try
// rematerializing it.
if (!isExtSubReg && !isInsSubReg &&
ReMaterializeTrivialDef(SrcInt, DstInt.reg, CopyMI))
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!isExtSubReg && !isInsSubReg &&
@ -1211,9 +1266,6 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
if (TargetRegisterInfo::isVirtualRegister(DstReg))
RemoveUnnecessaryKills(DstReg, *ResDstInt);
// SrcReg is guarateed to be the register whose live interval that is
// being merged.
li_->removeInterval(SrcReg);
if (isInsSubReg)
// Avoid:
// r1024 = op
@ -1223,6 +1275,10 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
RemoveDeadImpDef(DstReg, *ResDstInt);
UpdateRegDefsUses(SrcReg, DstReg, SubIdx);
// SrcReg is guarateed to be the register whose live interval that is
// being merged.
li_->removeInterval(SrcReg);
if (isEmpty) {
// Now the copy is being coalesced away, the val# previously defined
// by the copy is being defined by an IMPLICIT_DEF which defines a zero
@ -2018,6 +2074,7 @@ void SimpleRegisterCoalescing::printRegName(unsigned reg) const {
void SimpleRegisterCoalescing::releaseMemory() {
JoinedCopies.clear();
ReMatCopies.clear();
}
static bool isZeroLengthInterval(LiveInterval *li) {

7
lib/CodeGen/SimpleRegisterCoalescing.h
View File

@ -96,6 +96,10 @@ namespace llvm {
///
SmallPtrSet<MachineInstr*, 32> JoinedCopies;
/// ReMatCopies - Keep track of copies eliminated due to remat.
///
SmallPtrSet<MachineInstr*, 32> ReMatCopies;
public:
static char ID; // Pass identifcation, replacement for typeid
SimpleRegisterCoalescing() : MachineFunctionPass((intptr_t)&ID) {}
@ -194,6 +198,9 @@ namespace llvm {
bool RemoveCopyByCommutingDef(LiveInterval &IntA, LiveInterval &IntB,
MachineInstr *CopyMI);
bool ReMaterializeTrivialDef(LiveInterval &SrcInt, unsigned DstReg,
MachineInstr *CopyMI);
/// TurnCopyIntoImpDef - If source of the specified copy is an implicit def,
/// turn the copy into an implicit def.
bool TurnCopyIntoImpDef(MachineBasicBlock::iterator &I,

2
test/CodeGen/X86/2008-08-23-X86-64AsmBug.ll
View File

@ -1,4 +1,4 @@
; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin | not grep movd
; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin | grep movd | count 1
; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin | grep movq
; PR2677

4
test/CodeGen/X86/2008-08-25-AsmRegTypeMismatch.ll
View File

@ -1,5 +1,7 @@
; RUN: llvm-as < %s | llc -mcpu=yonah
; RUN: llvm-as < %s | llc -mcpu=yonah | grep pxor | count 2
; RUN: llvm-as < %s | llc -mcpu=yonah | not grep movapd
; PR2715
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"
%struct.XPTTypeDescriptorPrefix = type { i8 }