Reviewers: Vitaly, Mads Ager,
Description:
Fix an occasional crash in Assembler::ldr() for arm.
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.
Please review this at http://codereview.chromium.org/2454001/show
SVN Base: git://github.com/v8/v8.git
Affected files:
M src/arm/assembler-arm.cc
Index: src/arm/assembler-arm.cc
diff --git a/src/arm/assembler-arm.cc b/src/arm/assembler-arm.cc
index
6dd381febb26bacfc14bc3095594682b35e507f7..d8f859b5579ec59867b46471e91df43f6f711399
100644
--- a/src/arm/assembler-arm.cc
+++ b/src/arm/assembler-arm.cc
@@ -1213,31 +1213,31 @@ 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) &&
- 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 (can_peephole_optimize(2)) {
+ Instr push_instr = instr_at(pc_ - 2 * kInstrSize);
+ Instr pop_instr = instr_at(pc_ - 1 * kInstrSize);
+
+ 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());
+ }
}
}
}
--
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