AuroraMiddleware/v8
1
0
Fork 0
Code Issues 2 Pull Requests Releases Wiki Activity

Consistently assume that arithmetic operations can overflow unless one can prove the opposite.

Browse Source 
Previously, HDiv never had its CanOverflow flag cleared and HMod had
inverted logic (compared to HAdd, HSub and HMul). Minor cleanups on the way.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/14617015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14644 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
svenpanne@chromium.org 2013-05-13 13:48:15 +00:00
parent ca5fa6b2ce
commit c1bc396c2d
2 changed files with 26 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/hydrogen-instructions.cc
View File

@ -1445,6 +1445,16 @@ HValue* HMul::Canonicalize() {
}
HValue* HMod::Canonicalize() {
return this;
}
HValue* HDiv::Canonicalize() {
return this;
}
HValue* HChange::Canonicalize() {
return (from().Equals(to())) ? value() : this;
}
@ -1773,20 +1783,22 @@ 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;
@ -1799,16 +1811,17 @@ 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;

5
src/hydrogen-instructions.h
View File

@ -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: