Revision: 7248
Author: [email protected]
Date: Thu Mar 17 11:14:21 2011
Log: X64: Port optimization of LMulI to x64.
Review URL: http://codereview.chromium.org/6701003
http://code.google.com/p/v8/source/detail?r=7248
Modified:
/branches/bleeding_edge/src/x64/lithium-codegen-x64.cc
=======================================
--- /branches/bleeding_edge/src/x64/lithium-codegen-x64.cc Thu Mar 17
07:30:48 2011
+++ /branches/bleeding_edge/src/x64/lithium-codegen-x64.cc Thu Mar 17
11:14:21 2011
@@ -864,16 +864,56 @@
__ movl(kScratchRegister, left);
}
+ bool can_overflow =
+ instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
if (right->IsConstantOperand()) {
int right_value = ToInteger32(LConstantOperand::cast(right));
- __ imull(left, left, Immediate(right_value));
+ if (right_value == -1) {
+ __ negl(left);
+ } else if (right_value == 0) {
+ __ xorl(left, left);
+ } else if (right_value == 2) {
+ __ addl(left, left);
+ } else if (!can_overflow) {
+ // If the multiplication is known to not overflow, we
+ // can use operations that don't set the overflow flag
+ // correctly.
+ switch (right_value) {
+ case 1:
+ // Do nothing.
+ break;
+ case 3:
+ __ leal(left, Operand(left, left, times_2, 0));
+ break;
+ case 4:
+ __ shll(left, Immediate(2));
+ break;
+ case 5:
+ __ leal(left, Operand(left, left, times_4, 0));
+ break;
+ case 8:
+ __ shll(left, Immediate(3));
+ break;
+ case 9:
+ __ leal(left, Operand(left, left, times_8, 0));
+ break;
+ case 16:
+ __ shll(left, Immediate(4));
+ break;
+ default:
+ __ imull(left, left, Immediate(right_value));
+ break;
+ }
+ } else {
+ __ imull(left, left, Immediate(right_value));
+ }
} else if (right->IsStackSlot()) {
__ imull(left, ToOperand(right));
} else {
__ imull(left, ToRegister(right));
}
- if (instr->hydrogen()->CheckFlag(HValue::kCanOverflow)) {
+ if (can_overflow) {
DeoptimizeIf(overflow, instr->environment());
}
--
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