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Re-enable branchfolding common code hoisting optimization. Fixed a liveness test bug and also taught it to update liveins.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131241 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2011-05-12 20:30:01 +00:00
parent b11f80e94b
commit 7139d35165
2 changed files with 66 additions and 13 deletions
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51
lib/CodeGen/BranchFolding.cpp
View File

@ -1354,10 +1354,6 @@ ReoptimizeBlock:
/// NOTE: This optimization does not update live-in information so it must be
/// run after all passes that require correct liveness information.
bool BranchFolder::HoistCommonCode(MachineFunction &MF) {
#if 1
// FIXME: Temporarily disabled.
return false;
#endif
bool MadeChange = false;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ) {
MachineBasicBlock *MBB = I++;
@ -1472,10 +1468,10 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
Uses.erase(Reg);
for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
Uses.erase(*SR); // Use getSubRegisters to be conservative
Defs.insert(Reg);
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
Defs.insert(*AS);
}
Defs.insert(Reg);
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
Defs.insert(*AS);
}
}
@ -1511,7 +1507,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
return false;
bool HasDups = false;
SmallSet<unsigned, 4> LocalDefs;
SmallVector<unsigned, 4> LocalDefs;
SmallSet<unsigned, 4> LocalDefsSet;
MachineBasicBlock::iterator TIB = TBB->begin();
MachineBasicBlock::iterator FIB = FBB->begin();
MachineBasicBlock::iterator TIE = TBB->end();
@ -1568,11 +1565,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
IsSafe = false;
break;
}
LocalDefs.insert(Reg);
for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
LocalDefs.insert(*SR);
} else if (!LocalDefs.count(Reg)) {
} else if (!LocalDefsSet.count(Reg)) {
if (Defs.count(Reg)) {
// Use is defined by the instruction at the point of insertion.
IsSafe = false;
@ -1587,6 +1580,28 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
if (!TIB->isSafeToMove(TII, 0, DontMoveAcrossStore))
break;
// Track local defs so we can update liveins.
for (unsigned i = 0, e = TIB->getNumOperands(); i != e; ++i) {
MachineOperand &MO = TIB->getOperand(i);
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
if (MO.isDef()) {
if (!MO.isDead()) {
LocalDefs.push_back(Reg);
LocalDefsSet.insert(Reg);
for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
LocalDefsSet.insert(*SR);
}
} else if (MO.isKill() && LocalDefsSet.count(Reg)) {
LocalDefsSet.erase(Reg);
for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
LocalDefsSet.erase(*SR);
}
}
HasDups = true;;
++TIB;
++FIB;
@ -1597,6 +1612,16 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
MBB->splice(Loc, TBB, TBB->begin(), TIB);
FBB->erase(FBB->begin(), FIB);
// Update livein's.
for (unsigned i = 0, e = LocalDefs.size(); i != e; ++i) {
unsigned Def = LocalDefs[i];
if (LocalDefsSet.count(Def)) {
TBB->addLiveIn(Def);
FBB->addLiveIn(Def);
}
}
++NumHoist;
return true;
}

28
test/CodeGen/X86/hoist-common.ll Normal file
View File

@ -0,0 +1,28 @@
; RUN: llc < %s -march=x86-64 | FileCheck %s
; Common "xorb al, al" instruction in the two successor blocks should be
; moved to the entry block above the test + je.
; rdar://9145558
define zeroext i1 @t(i32 %c) nounwind ssp {
entry:
; CHECK: t:
; CHECK: xorb %al, %al
; CHECK: test
; CHECK: je
%tobool = icmp eq i32 %c, 0
br i1 %tobool, label %return, label %if.then
if.then:
; CHECK: callq
%call = tail call zeroext i1 (...)* @foo() nounwind
br label %return
return:
; CHECK: ret
%retval.0 = phi i1 [ %call, %if.then ], [ false, %entry ]
ret i1 %retval.0
}
declare zeroext i1 @foo(...)