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Fix for when array bounds check elimination tries to modify a phi index.

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BUG=

Review URL: https://chromiumcodereview.appspot.com/11486007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13193 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
mmassi@chromium.org 2012-12-11 14:23:04 +00:00
parent ca3ea142be
commit ae54f9cfe0
2 changed files with 69 additions and 21 deletions
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66
src/hydrogen.cc
View File

@ -3446,7 +3446,10 @@ class BoundsCheckBbData: public ZoneObject {
// (either upper or lower; note that HasSingleCheck() becomes false).
// Otherwise one of the current checks is modified so that it also covers
// new_offset, and new_check is removed.
void CoverCheck(HBoundsCheck* new_check,
//
// If the check cannot be modified because the context is unknown it
// returns false, otherwise it returns true.
bool CoverCheck(HBoundsCheck* new_check,
int32_t new_offset) {
ASSERT(new_check->index()->representation().IsInteger32());
bool keep_new_check = false;
@ -3457,12 +3460,13 @@ class BoundsCheckBbData: public ZoneObject {
keep_new_check = true;
upper_check_ = new_check;
} else {
BuildOffsetAdd(upper_check_,
&added_upper_index_,
&added_upper_offset_,
Key()->IndexBase(),
new_check->index()->representation(),
new_offset);
bool result = BuildOffsetAdd(upper_check_,
&added_upper_index_,
&added_upper_offset_,
Key()->IndexBase(),
new_check->index()->representation(),
new_offset);
if (!result) return false;
upper_check_->SetOperandAt(0, added_upper_index_);
}
} else if (new_offset < lower_offset_) {
@ -3471,12 +3475,13 @@ class BoundsCheckBbData: public ZoneObject {
keep_new_check = true;
lower_check_ = new_check;
} else {
BuildOffsetAdd(lower_check_,
&added_lower_index_,
&added_lower_offset_,
Key()->IndexBase(),
new_check->index()->representation(),
new_offset);
bool result = BuildOffsetAdd(lower_check_,
&added_lower_index_,
&added_lower_offset_,
Key()->IndexBase(),
new_check->index()->representation(),
new_offset);
if (!result) return false;
lower_check_->SetOperandAt(0, added_lower_index_);
}
} else {
@ -3486,6 +3491,8 @@ class BoundsCheckBbData: public ZoneObject {
if (!keep_new_check) {
new_check->DeleteAndReplaceWith(NULL);
}
return true;
}
void RemoveZeroOperations() {
@ -3528,20 +3535,34 @@ class BoundsCheckBbData: public ZoneObject {
BoundsCheckBbData* next_in_bb_;
BoundsCheckBbData* father_in_dt_;
void BuildOffsetAdd(HBoundsCheck* check,
// Given an existing add instruction and a bounds check it tries to
// find the current context (either of the add or of the check index).
HValue* IndexContext(HAdd* add, HBoundsCheck* check) {
if (add != NULL) {
return add->context();
}
if (check->index()->IsBinaryOperation()) {
return HBinaryOperation::cast(check->index())->context();
}
return NULL;
}
// This function returns false if it cannot build the add because the
// current context cannot be determined.
bool BuildOffsetAdd(HBoundsCheck* check,
HAdd** add,
HConstant** constant,
HValue* original_value,
Representation representation,
int32_t new_offset) {
HValue* index_context = IndexContext(*add, check);
if (index_context == NULL) return false;
HConstant* new_constant = new(BasicBlock()->zone())
HConstant(new_offset, Representation::Integer32());
if (*add == NULL) {
new_constant->InsertBefore(check);
// Because of the bounds checks elimination algorithm, the index is always
// an HAdd or an HSub here, so we can safely cast to an HBinaryOperation.
HValue* context = HBinaryOperation::cast(check->index())->context();
*add = new(BasicBlock()->zone()) HAdd(context,
*add = new(BasicBlock()->zone()) HAdd(index_context,
original_value,
new_constant);
(*add)->AssumeRepresentation(representation);
@ -3551,6 +3572,7 @@ class BoundsCheckBbData: public ZoneObject {
(*constant)->DeleteAndReplaceWith(new_constant);
}
*constant = new_constant;
return true;
}
void RemoveZeroAdd(HAdd** add, HConstant** constant) {
@ -3625,9 +3647,11 @@ void HGraph::EliminateRedundantBoundsChecks(HBasicBlock* bb,
*data_p = bb_data_list;
} else if (data->OffsetIsCovered(offset)) {
check->DeleteAndReplaceWith(NULL);
} else if (data->BasicBlock() == bb) {
data->CoverCheck(check, offset);
} else {
} else if (data->BasicBlock() != bb ||
!data->CoverCheck(check, offset)) {
// If the check is in the current BB we try to modify it by calling
// "CoverCheck", but if also that fails we record the current offsets
// in a new data instance because from now on they are covered.
int32_t new_lower_offset = offset < data->LowerOffset()
? offset
: data->LowerOffset();

24
test/mjsunit/array-bounds-check-removal.js
View File

@ -178,5 +178,29 @@ short_test(a, 0);
assertTrue(%GetOptimizationStatus(short_test) != 1);
// A test for when we would modify a phi index.
var data_phi = [0, 1, 2, 3, 4, 5, 6, 7, 8];
function test_phi(a, base, check) {
var index;
if (check) {
index = base + 1;
} else {
index = base + 2;
}
var result = a[index];
result += a[index + 1];
result += a[index - 1];
return result;
}
var result_phi = 0;
result_phi = test_phi(data_phi, 3, true);
assertEquals(12, result_phi);
result_phi = test_phi(data_phi, 3, true);
assertEquals(12, result_phi);
%OptimizeFunctionOnNextCall(test_phi);
result_phi = test_phi(data_phi, 3, true);
assertEquals(12, result_phi);
gc();