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Fix an occasional crash in Assembler::ldr() for arm.

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A peephole optimization can be attempted on a buffer that contains only a single command. The crash happens when running debug on Snow Leopard with --simulator=arm.

Review URL: http://codereview.chromium.org/2454001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4762 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
dimich@chromium.org 2010-06-01 08:01:50 +00:00
parent 019b8c4511
commit 610ad370a3
1 changed files with 25 additions and 24 deletions
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49
src/arm/assembler-arm.cc
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@ -1213,31 +1213,32 @@ void Assembler::ldr(Register dst, const MemOperand& src, Condition cond) {
// Both instructions can be eliminated if ry = rx.
// If ry != rx, a register copy from ry to rx is inserted
// after eliminating the push and the pop instructions.
Instr push_instr = instr_at(pc_ - 2 * kInstrSize);
Instr pop_instr = instr_at(pc_ - 1 * kInstrSize);
if (can_peephole_optimize(2)) {
Instr push_instr = instr_at(pc_ - 2 * kInstrSize);
Instr pop_instr = instr_at(pc_ - 1 * kInstrSize);
if (can_peephole_optimize(2) &&
IsPush(push_instr) &&
IsPop(pop_instr)) {
if ((pop_instr & kRdMask) != (push_instr & kRdMask)) {
// For consecutive push and pop on different registers,
// we delete both the push & pop and insert a register move.
// push ry, pop rx --> mov rx, ry
Register reg_pushed, reg_popped;
reg_pushed = GetRd(push_instr);
reg_popped = GetRd(pop_instr);
pc_ -= 2 * kInstrSize;
// Insert a mov instruction, which is better than a pair of push & pop
mov(reg_popped, reg_pushed);
if (FLAG_print_peephole_optimization) {
PrintF("%x push/pop (diff reg) replaced by a reg move\n", pc_offset());
}
} else {
// For consecutive push and pop on the same register,
// both the push and the pop can be deleted.
pc_ -= 2 * kInstrSize;
if (FLAG_print_peephole_optimization) {
PrintF("%x push/pop (same reg) eliminated\n", pc_offset());
if (IsPush(push_instr) && IsPop(pop_instr)) {
if ((pop_instr & kRdMask) != (push_instr & kRdMask)) {
// For consecutive push and pop on different registers,
// we delete both the push & pop and insert a register move.
// push ry, pop rx --> mov rx, ry
Register reg_pushed, reg_popped;
reg_pushed = GetRd(push_instr);
reg_popped = GetRd(pop_instr);
pc_ -= 2 * kInstrSize;
// Insert a mov instruction, which is better than a pair of push & pop
mov(reg_popped, reg_pushed);
if (FLAG_print_peephole_optimization) {
PrintF("%x push/pop (diff reg) replaced by a reg move\n",
pc_offset());
}
} else {
// For consecutive push and pop on the same register,
// both the push and the pop can be deleted.
pc_ -= 2 * kInstrSize;
if (FLAG_print_peephole_optimization) {
PrintF("%x push/pop (same reg) eliminated\n", pc_offset());
}
}
}
}