Reviewers: ulan, Benedikt Meurer,
Message:
On ARM there is no reason for the division to always overwrite its left
input.
Minor clean up on deoptimisation code too.
Description:
ARM: Tweak the integer division operation.
BUG=none
TEST=test/mjsunit/lithium/DivI.js
Please review this at https://codereview.chromium.org/23536045/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+51, -27 lines):
M src/arm/lithium-arm.cc
M src/arm/lithium-codegen-arm.cc
A + test/mjsunit/lithium/DivI.js
Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index
7f504ea4ad4452d7da59d63bb192172fd021abee..d3ac5e0dfebf67c4ed54481d8669852b842c1c83
100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1373,9 +1373,8 @@ LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
if (instr->HasPowerOf2Divisor()) {
ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
LOperand* value = UseRegisterAtStart(instr->left());
- LDivI* div =
- new(zone()) LDivI(value, UseOrConstant(instr->right()), NULL);
- return AssignEnvironment(DefineSameAsFirst(div));
+ LDivI* div = new(zone()) LDivI(value, UseConstant(instr->right()),
NULL);
+ return AssignEnvironment(DefineAsRegister(div));
}
LOperand* dividend = UseRegister(instr->left());
LOperand* divisor = UseRegister(instr->right());
Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index
b7fc3b6055c67704f1065e3f232f039aa52bb745..b01f840c63140aff23c46f227798c2592a52db22
100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -1383,7 +1383,8 @@ void LCodeGen::EmitSignedIntegerDivisionByConstant(
void LCodeGen::DoDivI(LDivI* instr) {
if (instr->hydrogen()->HasPowerOf2Divisor()) {
- Register dividend = ToRegister(instr->left());
+ const Register dividend = ToRegister(instr->left());
+ const Register result = ToRegister(instr->result());
int32_t divisor = instr->hydrogen()->right()->GetInteger32Constant();
int32_t test_value = 0;
int32_t power = 0;
@@ -1394,7 +1395,7 @@ void LCodeGen::DoDivI(LDivI* instr) {
} else {
// Check for (0 / -x) that will produce negative zero.
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
- __ tst(dividend, Operand(dividend));
+ __ cmp(dividend, Operand::Zero());
DeoptimizeIf(eq, instr->environment());
}
// Check for (kMinInt / -1).
@@ -1409,20 +1410,26 @@ void LCodeGen::DoDivI(LDivI* instr) {
if (test_value != 0) {
if (instr->hydrogen()->CheckFlag(
HInstruction::kAllUsesTruncatingToInt32)) {
- __ cmp(dividend, Operand(0));
- __ rsb(dividend, dividend, Operand(0), LeaveCC, lt);
- __ mov(dividend, Operand(dividend, ASR, power));
- if (divisor > 0) __ rsb(dividend, dividend, Operand(0), LeaveCC,
lt);
- if (divisor < 0) __ rsb(dividend, dividend, Operand(0), LeaveCC,
gt);
+ __ sub(result, dividend, Operand::Zero(), SetCC);
+ __ rsb(result, result, Operand::Zero(), LeaveCC, lt);
+ __ mov(result, Operand(result, ASR, power));
+ if (divisor > 0) __ rsb(result, result, Operand::Zero(), LeaveCC,
lt);
+ if (divisor < 0) __ rsb(result, result, Operand::Zero(), LeaveCC,
gt);
return; // Don't fall through to "__ rsb" below.
} else {
// Deoptimize if remainder is not 0.
__ tst(dividend, Operand(test_value));
DeoptimizeIf(ne, instr->environment());
- __ mov(dividend, Operand(dividend, ASR, power));
+ __ mov(result, Operand(dividend, ASR, power));
+ if (divisor < 0) __ rsb(result, result, Operand(0));
+ }
+ } else {
+ if (divisor < 0) {
+ __ rsb(result, dividend, Operand(0));
+ } else {
+ __ Move(result, dividend);
}
}
- if (divisor < 0) __ rsb(dividend, dividend, Operand(0));
return;
}
@@ -1439,12 +1446,15 @@ void LCodeGen::DoDivI(LDivI* instr) {
// Check for (0 / -x) that will produce negative zero.
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
- Label left_not_zero;
+ Label positive;
+ if (!instr->hydrogen()->CheckFlag(HValue::kCanBeDivByZero)) {
+ // Do the test only if it hadn't be done above.
+ __ cmp(right, Operand::Zero());
+ }
+ __ b(pl, &positive);
__ cmp(left, Operand::Zero());
- __ b(ne, &left_not_zero);
- __ cmp(right, Operand::Zero());
- DeoptimizeIf(mi, instr->environment());
- __ bind(&left_not_zero);
+ DeoptimizeIf(eq, instr->environment());
+ __ bind(&positive);
}
// Check for (kMinInt / -1).
Index: test/mjsunit/lithium/DivI.js
diff --git a/test/mjsunit/constant-compare-nil-value.js
b/test/mjsunit/lithium/DivI.js
similarity index 73%
copy from test/mjsunit/constant-compare-nil-value.js
copy to test/mjsunit/lithium/DivI.js
index
9f5b2adb063abc0c7920d8dee30edb7ee6eb1ff9..5420d8c8d0ab0adc715683fd95f41a34e9373fc0
100644
--- a/test/mjsunit/constant-compare-nil-value.js
+++ b/test/mjsunit/lithium/DivI.js
@@ -25,18 +25,33 @@
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --no-use-osr
-function inlined() {
- return 1;
+function foo(a, b) {
+ var result = a / 35;
+ result += 50 / b;
+ result += a / b;
+ result += a / -1;
+ result += a / 1;
+ result += a / 4;
+ result += a / -4;
+ return result / b;
}
-function foo() {
- if ((inlined() + 0.5) == null) return "null";
- return "non-null";
+foo(700, 5);
+var r1 = foo(700, 5);
+%OptimizeFunctionOnNextCall(foo);
+var r2 = foo(700, 5);
+
+assertEquals(r1, r2);
+
+function boo(value) {
+ return value / -1;
}
-assertEquals("non-null", foo());
-assertEquals("non-null", foo());
-%OptimizeFunctionOnNextCall(foo);
-assertEquals("non-null", foo());
+// Test deoptimization of MinInt / -1.
+assertEquals(2147483600, boo(-2147483600));
+assertEquals(2147483600, boo(-2147483600));
+%OptimizeFunctionOnNextCall(boo);
+assertEquals(2147483600, boo(-2147483600));
+assertEquals(2147483648, boo(-2147483648));
--
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