Reviewers: Jakob,
Description:
Consistently assume that arithmetic operations can overflow unless one can
prove
the opposite.
This is a refactoring only: Previously, HDiv never had its CanOverflow flag
cleared and HMod had inverted logic (compared to HAdd, HSub and HMul). Minor
cleanups on the way.
Please review this at https://codereview.chromium.org/14617015/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/hydrogen-instructions.h
M src/hydrogen-instructions.cc
Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index
f38fb7d5e3d4312383c198cf23b25a7cf2f8f602..8ca929a752cb73b24575c4e54cd792f64f89f242
100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1441,6 +1441,16 @@ HValue* HMul::Canonicalize() {
}
+HValue* HMod::Canonicalize() {
+ return this;
+}
+
+
+HValue* HDiv::Canonicalize() {
+ return this;
+}
+
+
HValue* HChange::Canonicalize() {
return (from().Equals(to())) ? value() : this;
}
@@ -1769,20 +1779,22 @@ Range* HMul::InferRange(Zone* zone) {
Range* HDiv::InferRange(Zone* zone) {
if (representation().IsInteger32()) {
+ Range* a = left()->range();
+ Range* b = right()->range();
Range* result = new(zone) Range();
- if (left()->range()->CanBeMinusZero()) {
+ if (a->CanBeMinusZero()) {
result->set_can_be_minus_zero(true);
}
- if (left()->range()->CanBeZero() && right()->range()->CanBeNegative())
{
+ if (a->CanBeZero() && b->CanBeNegative()) {
result->set_can_be_minus_zero(true);
}
- if (right()->range()->Includes(-1) &&
left()->range()->Includes(kMinInt)) {
- SetFlag(HValue::kCanOverflow);
+ if (!a->Includes(kMinInt) || !b->Includes(-1)) {
+ ClearFlag(HValue::kCanOverflow);
}
- if (!right()->range()->CanBeZero()) {
+ if (!b->CanBeZero()) {
ClearFlag(HValue::kCanBeDivByZero);
}
return result;
@@ -1795,16 +1807,17 @@ Range* HDiv::InferRange(Zone* zone) {
Range* HMod::InferRange(Zone* zone) {
if (representation().IsInteger32()) {
Range* a = left()->range();
+ Range* b = right()->range();
Range* result = new(zone) Range();
if (a->CanBeMinusZero() || a->CanBeNegative()) {
result->set_can_be_minus_zero(true);
}
- if (right()->range()->Includes(-1) &&
left()->range()->Includes(kMinInt)) {
- SetFlag(HValue::kCanOverflow);
+ if (!a->Includes(kMinInt) || !b->Includes(-1)) {
+ ClearFlag(HValue::kCanOverflow);
}
- if (!right()->range()->CanBeZero()) {
+ if (!b->CanBeZero()) {
ClearFlag(HValue::kCanBeDivByZero);
}
return result;
Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index
62c98153894c9103b51754b82d67a9a6775067ec..bd0eddf8443724a438ecfedacecc7cacaad58dce
100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -4414,6 +4414,8 @@ class HMod: public HArithmeticBinaryOperation {
virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
+ virtual HValue* Canonicalize();
+
DECLARE_CONCRETE_INSTRUCTION(Mod)
protected:
@@ -4425,6 +4427,7 @@ class HMod: public HArithmeticBinaryOperation {
HMod(HValue* context, HValue* left, HValue* right)
: HArithmeticBinaryOperation(context, left, right) {
SetFlag(kCanBeDivByZero);
+ SetFlag(kCanOverflow);
}
};
@@ -4448,6 +4451,8 @@ class HDiv: public HArithmeticBinaryOperation {
virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
+ virtual HValue* Canonicalize();
+
DECLARE_CONCRETE_INSTRUCTION(Div)
protected:
--
--
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