Revision: 21769
Author: [email protected]
Date: Wed Jun 11 13:29:25 2014 UTC
Log: Fixed flooring division by a power of 2, once again...
Avoid right shifts by zero bits: On ARM it actually means shifting by
32 bits (correctness issue) and on other platforms they are useless
(performance issue). This is fix for the fix in r20544.
BUG=v8:3259
LOG=y
[email protected]
Review URL: https://codereview.chromium.org/324403003
http://code.google.com/p/v8/source/detail?r=21769
Modified:
/branches/bleeding_edge/src/arm/lithium-codegen-arm.cc
/branches/bleeding_edge/src/arm64/lithium-codegen-arm64.cc
/branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc
/branches/bleeding_edge/src/x64/lithium-codegen-x64.cc
/branches/bleeding_edge/test/mjsunit/mjsunit.status
=======================================
--- /branches/bleeding_edge/src/arm/lithium-codegen-arm.cc Wed Jun 11
09:09:15 2014 UTC
+++ /branches/bleeding_edge/src/arm/lithium-codegen-arm.cc Wed Jun 11
13:29:25 2014 UTC
@@ -1469,20 +1469,22 @@
DeoptimizeIf(eq, instr->environment());
}
- // If the negation could not overflow, simply shifting is OK.
- if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
- __ mov(result, Operand(dividend, ASR, shift));
+ // Dividing by -1 is basically negation, unless we overflow.
+ if (divisor == -1) {
+ if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ DeoptimizeIf(vs, instr->environment());
+ }
return;
}
- // Dividing by -1 is basically negation, unless we overflow.
- if (divisor == -1) {
- DeoptimizeIf(vs, instr->environment());
+ // If the negation could not overflow, simply shifting is OK.
+ if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ __ mov(result, Operand(result, ASR, shift));
return;
}
__ mov(result, Operand(kMinInt / divisor), LeaveCC, vs);
- __ mov(result, Operand(dividend, ASR, shift), LeaveCC, vc);
+ __ mov(result, Operand(result, ASR, shift), LeaveCC, vc);
}
=======================================
--- /branches/bleeding_edge/src/arm64/lithium-codegen-arm64.cc Wed Jun 11
09:09:15 2014 UTC
+++ /branches/bleeding_edge/src/arm64/lithium-codegen-arm64.cc Wed Jun 11
13:29:25 2014 UTC
@@ -3933,19 +3933,21 @@
DeoptimizeIf(eq, instr->environment());
}
- // If the negation could not overflow, simply shifting is OK.
- if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
- __ Mov(result, Operand(dividend, ASR, shift));
+ // Dividing by -1 is basically negation, unless we overflow.
+ if (divisor == -1) {
+ if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ DeoptimizeIf(vs, instr->environment());
+ }
return;
}
- // Dividing by -1 is basically negation, unless we overflow.
- if (divisor == -1) {
- DeoptimizeIf(vs, instr->environment());
+ // If the negation could not overflow, simply shifting is OK.
+ if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ __ Mov(result, Operand(dividend, ASR, shift));
return;
}
- __ Asr(result, dividend, shift);
+ __ Asr(result, result, shift);
__ Csel(result, result, kMinInt / divisor, vc);
}
=======================================
--- /branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc Wed Jun 11
09:09:15 2014 UTC
+++ /branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc Wed Jun 11
13:29:25 2014 UTC
@@ -1353,14 +1353,17 @@
DeoptimizeIf(zero, instr->environment());
}
- if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
- __ sar(dividend, shift);
+ // Dividing by -1 is basically negation, unless we overflow.
+ if (divisor == -1) {
+ if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ DeoptimizeIf(overflow, instr->environment());
+ }
return;
}
- // Dividing by -1 is basically negation, unless we overflow.
- if (divisor == -1) {
- DeoptimizeIf(overflow, instr->environment());
+ // If the negation could not overflow, simply shifting is OK.
+ if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ __ sar(dividend, shift);
return;
}
=======================================
--- /branches/bleeding_edge/src/x64/lithium-codegen-x64.cc Wed Jun 11
09:09:15 2014 UTC
+++ /branches/bleeding_edge/src/x64/lithium-codegen-x64.cc Wed Jun 11
13:29:25 2014 UTC
@@ -1133,19 +1133,20 @@
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
DeoptimizeIf(zero, instr->environment());
}
+
+ // Dividing by -1 is basically negation, unless we overflow.
+ if (divisor == -1) {
+ if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ DeoptimizeIf(overflow, instr->environment());
+ }
+ return;
+ }
// If the negation could not overflow, simply shifting is OK.
if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
__ sarl(dividend, Immediate(shift));
return;
}
-
- // Note that we could emit branch-free code, but that would need one more
- // register.
- if (divisor == -1) {
- DeoptimizeIf(overflow, instr->environment());
- return;
- }
Label not_kmin_int, done;
__ j(no_overflow, ¬_kmin_int, Label::kNear);
=======================================
--- /branches/bleeding_edge/test/mjsunit/mjsunit.status Thu Jun 5 12:53:36
2014 UTC
+++ /branches/bleeding_edge/test/mjsunit/mjsunit.status Wed Jun 11 13:29:25
2014 UTC
@@ -308,10 +308,6 @@
# Currently always deopt on minus zero
'math-floor-of-div-minus-zero': [SKIP],
- # Issue 3259.
- 'math-floor-of-div-nosudiv': [PASS, FAIL],
- 'math-floor-of-div': [PASS, FAIL],
-
############################################################################
# Slow tests.
'regress/regress-2185-2': [PASS, SLOW],
--
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