llvm/lib/CodeGen/MachineCopyPropagation.cpp

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//===- MachineCopyPropagation.cpp - Machine Copy Propagation Pass ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is an extremely simple MachineInstr-level copy propagation pass.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "codegen-cp"
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
STATISTIC(NumDeletes, "Number of dead copies deleted");
namespace {
class MachineCopyPropagation : public MachineFunctionPass {
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
MachineRegisterInfo *MRI;
public:
static char ID; // Pass identification, replacement for typeid
MachineCopyPropagation() : MachineFunctionPass(ID) {
initializeMachineCopyPropagationPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnMachineFunction(MachineFunction &MF);
private:
typedef SmallVector<unsigned, 4> DestList;
typedef DenseMap<unsigned, DestList> SourceMap;
void SourceNoLongerAvailable(unsigned Reg,
SourceMap &SrcMap,
DenseMap<unsigned, MachineInstr*> &AvailCopyMap);
bool CopyPropagateBlock(MachineBasicBlock &MBB);
void removeCopy(MachineInstr *MI);
};
}
char MachineCopyPropagation::ID = 0;
char &llvm::MachineCopyPropagationID = MachineCopyPropagation::ID;
INITIALIZE_PASS(MachineCopyPropagation, "machine-cp",
"Machine Copy Propagation Pass", false, false)
void
MachineCopyPropagation::SourceNoLongerAvailable(unsigned Reg,
SourceMap &SrcMap,
DenseMap<unsigned, MachineInstr*> &AvailCopyMap) {
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
SourceMap::iterator SI = SrcMap.find(*AI);
if (SI != SrcMap.end()) {
const DestList& Defs = SI->second;
for (DestList::const_iterator I = Defs.begin(), E = Defs.end();
I != E; ++I) {
unsigned MappedDef = *I;
// Source of copy is no longer available for propagation.
if (AvailCopyMap.erase(MappedDef)) {
for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
AvailCopyMap.erase(*SR);
}
}
}
}
}
static bool NoInterveningSideEffect(const MachineInstr *CopyMI,
const MachineInstr *MI) {
const MachineBasicBlock *MBB = CopyMI->getParent();
if (MI->getParent() != MBB)
return false;
MachineBasicBlock::const_iterator I = CopyMI;
MachineBasicBlock::const_iterator E = MBB->end();
MachineBasicBlock::const_iterator E2 = MI;
++I;
while (I != E && I != E2) {
if (I->hasUnmodeledSideEffects() || I->isCall() ||
I->isTerminator())
return false;
++I;
}
return true;
}
/// isNopCopy - Return true if the specified copy is really a nop. That is
/// if the source of the copy is the same of the definition of the copy that
/// supplied the source. If the source of the copy is a sub-register than it
/// must check the sub-indices match. e.g.
/// ecx = mov eax
/// al = mov cl
/// But not
/// ecx = mov eax
/// al = mov ch
static bool isNopCopy(MachineInstr *CopyMI, unsigned Def, unsigned Src,
const TargetRegisterInfo *TRI) {
unsigned SrcSrc = CopyMI->getOperand(1).getReg();
if (Def == SrcSrc)
return true;
if (TRI->isSubRegister(SrcSrc, Def)) {
unsigned SrcDef = CopyMI->getOperand(0).getReg();
unsigned SubIdx = TRI->getSubRegIndex(SrcSrc, Def);
if (!SubIdx)
return false;
return SubIdx == TRI->getSubRegIndex(SrcDef, Src);
}
return false;
}
// Remove MI from the function because it has been determined it is dead.
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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// Turn it into a noop KILL instruction as opposed to removing it to
// maintain imp-use/imp-def chains.
void MachineCopyPropagation::removeCopy(MachineInstr *MI) {
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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MI->setDesc(TII->get(TargetOpcode::KILL));
}
bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
SmallSetVector<MachineInstr*, 8> MaybeDeadCopies; // Candidates for deletion
DenseMap<unsigned, MachineInstr*> AvailCopyMap; // Def -> available copies map
DenseMap<unsigned, MachineInstr*> CopyMap; // Def -> copies map
SourceMap SrcMap; // Src -> Def map
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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DEBUG(dbgs() << "MCP: CopyPropagateBlock " << MBB.getName() << "\n");
bool Changed = false;
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E; ) {
MachineInstr *MI = &*I;
++I;
if (MI->isCopy()) {
unsigned Def = MI->getOperand(0).getReg();
unsigned Src = MI->getOperand(1).getReg();
if (TargetRegisterInfo::isVirtualRegister(Def) ||
TargetRegisterInfo::isVirtualRegister(Src))
report_fatal_error("MachineCopyPropagation should be run after"
" register allocation!");
DenseMap<unsigned, MachineInstr*>::iterator CI = AvailCopyMap.find(Src);
if (CI != AvailCopyMap.end()) {
MachineInstr *CopyMI = CI->second;
if (!MRI->isReserved(Def) &&
(!MRI->isReserved(Src) || NoInterveningSideEffect(CopyMI, MI)) &&
isNopCopy(CopyMI, Def, Src, TRI)) {
// The two copies cancel out and the source of the first copy
// hasn't been overridden, eliminate the second one. e.g.
// %ECX<def> = COPY %EAX<kill>
// ... nothing clobbered EAX.
// %EAX<def> = COPY %ECX
// =>
// %ECX<def> = COPY %EAX
//
// Also avoid eliminating a copy from reserved registers unless the
// definition is proven not clobbered. e.g.
// %RSP<def> = COPY %RAX
// CALL
// %RAX<def> = COPY %RSP
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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DEBUG(dbgs() << "MCP: copy is a NOP, removing: "; MI->dump());
// Clear any kills of Def between CopyMI and MI. This extends the
// live range.
for (MachineBasicBlock::iterator I = CopyMI, E = MI; I != E; ++I)
I->clearRegisterKills(Def, TRI);
removeCopy(MI);
Changed = true;
++NumDeletes;
continue;
}
}
// If Src is defined by a previous copy, it cannot be eliminated.
for (MCRegAliasIterator AI(Src, TRI, true); AI.isValid(); ++AI) {
CI = CopyMap.find(*AI);
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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if (CI != CopyMap.end()) {
DEBUG(dbgs() << "MCP: Copy is no longer dead: "; CI->second->dump());
MaybeDeadCopies.remove(CI->second);
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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}
}
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI->dump());
// Copy is now a candidate for deletion.
MaybeDeadCopies.insert(MI);
// If 'Src' is previously source of another copy, then this earlier copy's
// source is no longer available. e.g.
// %xmm9<def> = copy %xmm2
// ...
// %xmm2<def> = copy %xmm0
// ...
// %xmm2<def> = copy %xmm9
SourceNoLongerAvailable(Def, SrcMap, AvailCopyMap);
// Remember Def is defined by the copy.
// ... Make sure to clear the def maps of aliases first.
for (MCRegAliasIterator AI(Def, TRI, false); AI.isValid(); ++AI) {
CopyMap.erase(*AI);
AvailCopyMap.erase(*AI);
}
for (MCSubRegIterator SR(Def, TRI, /*IncludeSelf=*/true); SR.isValid();
++SR) {
CopyMap[*SR] = MI;
AvailCopyMap[*SR] = MI;
}
// Remember source that's copied to Def. Once it's clobbered, then
// it's no longer available for copy propagation.
if (std::find(SrcMap[Src].begin(), SrcMap[Src].end(), Def) ==
SrcMap[Src].end()) {
SrcMap[Src].push_back(Def);
}
continue;
}
// Not a copy.
SmallVector<unsigned, 2> Defs;
int RegMaskOpNum = -1;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegMask())
RegMaskOpNum = i;
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
if (TargetRegisterInfo::isVirtualRegister(Reg))
report_fatal_error("MachineCopyPropagation should be run after"
" register allocation!");
if (MO.isDef()) {
Defs.push_back(Reg);
continue;
}
// If 'Reg' is defined by a copy, the copy is no longer a candidate
// for elimination.
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
DenseMap<unsigned, MachineInstr*>::iterator CI = CopyMap.find(*AI);
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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if (CI != CopyMap.end()) {
DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
MaybeDeadCopies.remove(CI->second);
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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}
}
}
// The instruction has a register mask operand which means that it clobbers
// a large set of registers. It is possible to use the register mask to
// prune the available copies, but treat it like a basic block boundary for
// now.
if (RegMaskOpNum >= 0) {
// Erase any MaybeDeadCopies whose destination register is clobbered.
const MachineOperand &MaskMO = MI->getOperand(RegMaskOpNum);
for (SmallSetVector<MachineInstr*, 8>::iterator
DI = MaybeDeadCopies.begin(), DE = MaybeDeadCopies.end();
DI != DE; ++DI) {
unsigned Reg = (*DI)->getOperand(0).getReg();
if (MRI->isReserved(Reg) || !MaskMO.clobbersPhysReg(Reg))
continue;
MachineCopyPropagation has special logic for removing COPY instructions. It will remove plain COPYs using eraseFromParent(), but if the COPY has imp-defs/imp-uses it will convert it to a KILL, to keep the imp-def around. This actually totally breaks and causes the machine verifier to cry in several cases, one of which being: %RAX<def> = COPY %RCX<kill> %ECX<def> = COPY %EAX<kill>, %RAX<imp-use,kill> These subregister copies are together identified as noops, so are both removed. However, the second one as it has an imp-use gets converted into a kill: %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> As the original COPY has been removed, the verifier goes into tears at the use of undefined EAX and RAX. There are several hacky solutions to this hacky problem (which is all to do with imp-use/def weirdnesses), but the least hacky I've come up with is to *always* remove COPYs by converting to KILLs. KILLs are no-ops to the code generator so the generated code doesn't change (which is why they were partially used in the first place), but using them also keeps the def/use and imp-def/imp-use chains alive: %RAX<def> = KILL %RCX<kill> %ECX<def> = KILL %EAX<kill>, %RAX<imp-use,kill> The patch passes all test cases including the ones that check the removal of MOVs in this circumstance, along with an extra test I added to check subregister behaviour (which made the machine verifier fall over before my patch). The patch also adds some DEBUG() statements because the file hadn't got any. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199797 91177308-0d34-0410-b5e6-96231b3b80d8
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DEBUG(dbgs() << "MCP: Removing copy due to regmask clobbering: ";
(*DI)->dump());
removeCopy(*DI);
Changed = true;
++NumDeletes;
}
// Clear all data structures as if we were beginning a new basic block.
MaybeDeadCopies.clear();
AvailCopyMap.clear();
CopyMap.clear();
SrcMap.clear();
continue;
}
for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
unsigned Reg = Defs[i];
// No longer defined by a copy.
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
CopyMap.erase(*AI);
AvailCopyMap.erase(*AI);
}
// If 'Reg' is previously source of a copy, it is no longer available for
// copy propagation.
SourceNoLongerAvailable(Reg, SrcMap, AvailCopyMap);
}
}
// If MBB doesn't have successors, delete the copies whose defs are not used.
// If MBB does have successors, then conservative assume the defs are live-out
// since we don't want to trust live-in lists.
if (MBB.succ_empty()) {
for (SmallSetVector<MachineInstr*, 8>::iterator
DI = MaybeDeadCopies.begin(), DE = MaybeDeadCopies.end();
DI != DE; ++DI) {
if (!MRI->isReserved((*DI)->getOperand(0).getReg())) {
removeCopy(*DI);
Changed = true;
++NumDeletes;
}
}
}
return Changed;
}
bool MachineCopyPropagation::runOnMachineFunction(MachineFunction &MF) {
bool Changed = false;
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
MRI = &MF.getRegInfo();
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
Changed |= CopyPropagateBlock(*I);
return Changed;
}