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Fix a bug in the -regalloc=fast handling of exotic two-address instruction with

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multiple defs, like t2LDRSB_POST.

The first def could accidentally steal the physreg that the second, tied def was
required to be allocated to.

Now, the tied use-def is treated more like an early clobber, and the physreg is
reserved before allocating the other defs.

This would never be a problem when the tied def was the only def which is the
usual case.

This fixes MallocBench/gs for thumb2 -O0.

llvm-svn: 109715
This commit is contained in:
Jakob Stoklund Olesen 2010-07-29 00:52:19 +00:00
parent 6a7ab2405c
commit 7f337a8e64
1 changed files with 11 additions and 3 deletions
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14
lib/CodeGen/RegAllocFast.cpp
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@ -847,13 +847,18 @@ void RAFast::AllocateBasicBlock() {
// operands. If there are also physical defs, these registers must avoid // operands. If there are also physical defs, these registers must avoid
// both physical defs and uses, making them more constrained than normal // both physical defs and uses, making them more constrained than normal
// operands. // operands.
// Similarly, if there are multiple defs and tied operands, we must make sure
// the same register is allocated to uses and defs.
// We didn't detect inline asm tied operands above, so just make this extra // We didn't detect inline asm tied operands above, so just make this extra
// pass for all inline asm. // pass for all inline asm.
if (MI->isInlineAsm() || hasEarlyClobbers || hasPartialRedefs || if (MI->isInlineAsm() || hasEarlyClobbers || hasPartialRedefs ||
(hasTiedOps && hasPhysDefs)) { (hasTiedOps && (hasPhysDefs || TID.getNumDefs() > 1))) {
handleThroughOperands(MI, VirtDead); handleThroughOperands(MI, VirtDead);
// Don't attempt coalescing when we have funny stuff going on. // Don't attempt coalescing when we have funny stuff going on.
CopyDst = 0; CopyDst = 0;
// Pretend we have early clobbers so the use operands get marked below.
// This is not necessary for the common case of a single tied use.
hasEarlyClobbers = true;
} }
// Second scan. // Second scan.
@ -874,14 +879,17 @@ void RAFast::AllocateBasicBlock() {
MRI->addPhysRegsUsed(UsedInInstr); MRI->addPhysRegsUsed(UsedInInstr);
// Track registers defined by instruction - early clobbers at this point. // Track registers defined by instruction - early clobbers and tied uses at
// this point.
UsedInInstr.reset(); UsedInInstr.reset();
if (hasEarlyClobbers) { if (hasEarlyClobbers) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i); MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef()) continue; if (!MO.isReg()) continue;
unsigned Reg = MO.getReg(); unsigned Reg = MO.getReg();
if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue; if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
// Look for physreg defs and tied uses.
if (!MO.isDef() && !MI->isRegTiedToDefOperand(i)) continue;
UsedInInstr.set(Reg); UsedInInstr.set(Reg);
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
UsedInInstr.set(*AS); UsedInInstr.set(*AS);