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Add FLAG_trace_bce

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R=ulan@chromium.org

Review URL: https://codereview.chromium.org/203193006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20088 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
jkummerow@chromium.org 2014-03-19 16:03:56 +00:00
parent d9b6b6439d
commit da6e5ebcdf
2 changed files with 43 additions and 3 deletions
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1
src/flag-definitions.h
View File

@ -302,6 +302,7 @@ DEFINE_bool(polymorphic_inlining, true, "polymorphic inlining")
DEFINE_bool(use_osr, true, "use on-stack replacement")
DEFINE_bool(array_bounds_checks_elimination, true,
"perform array bounds checks elimination")
DEFINE_bool(trace_bce, false, "trace array bounds check elimination")
DEFINE_bool(array_bounds_checks_hoisting, false,
"perform array bounds checks hoisting")
DEFINE_bool(array_index_dehoisting, true,

45
src/hydrogen-bce.cc
View File

@ -30,6 +30,7 @@
namespace v8 {
namespace internal {
// We try to "factor up" HBoundsCheck instructions towards the root of the
// dominator tree.
// For now we handle checks where the index is like "exp + int32value".
@ -173,7 +174,7 @@ class BoundsCheckBbData: public ZoneObject {
keep_new_check = true;
upper_check_ = new_check;
} else {
TightenCheck(upper_check_, new_check);
TightenCheck(upper_check_, new_check, new_offset);
UpdateUpperOffsets(upper_check_, upper_offset_);
}
} else if (new_offset < lower_offset_) {
@ -182,7 +183,7 @@ class BoundsCheckBbData: public ZoneObject {
keep_new_check = true;
lower_check_ = new_check;
} else {
TightenCheck(lower_check_, new_check);
TightenCheck(lower_check_, new_check, new_offset);
UpdateLowerOffsets(lower_check_, lower_offset_);
}
} else {
@ -191,12 +192,20 @@ class BoundsCheckBbData: public ZoneObject {
}
if (!keep_new_check) {
if (FLAG_trace_bce) {
OS::Print("Eliminating check #%d after tightening\n",
new_check->id());
}
new_check->block()->graph()->isolate()->counters()->
bounds_checks_eliminated()->Increment();
new_check->DeleteAndReplaceWith(new_check->ActualValue());
} else {
HBoundsCheck* first_check = new_check == lower_check_ ? upper_check_
: lower_check_;
if (FLAG_trace_bce) {
OS::Print("Moving second check #%d after first check #%d\n",
new_check->id(), first_check->id());
}
// The length is guaranteed to be live at first_check.
ASSERT(new_check->length() == first_check->length());
HInstruction* old_position = new_check->next();
@ -275,11 +284,16 @@ class BoundsCheckBbData: public ZoneObject {
}
void TightenCheck(HBoundsCheck* original_check,
HBoundsCheck* tighter_check) {
HBoundsCheck* tighter_check,
int32_t new_offset) {
ASSERT(original_check->length() == tighter_check->length());
MoveIndexIfNecessary(tighter_check->index(), original_check, tighter_check);
original_check->ReplaceAllUsesWith(original_check->index());
original_check->SetOperandAt(0, tighter_check->index());
if (FLAG_trace_bce) {
OS::Print("Tightened check #%d with offset %d from #%d\n",
original_check->id(), new_offset, tighter_check->id());
}
}
DISALLOW_COPY_AND_ASSIGN(BoundsCheckBbData);
@ -389,11 +403,32 @@ BoundsCheckBbData* HBoundsCheckEliminationPhase::PreProcessBlock(
bb_data_list,
NULL);
*data_p = bb_data_list;
if (FLAG_trace_bce) {
OS::Print("Fresh bounds check data for block #%d: [%d]\n",
bb->block_id(), offset);
}
} else if (data->OffsetIsCovered(offset)) {
bb->graph()->isolate()->counters()->
bounds_checks_eliminated()->Increment();
if (FLAG_trace_bce) {
OS::Print("Eliminating bounds check #%d, offset %d is covered\n",
check->id(), offset);
}
check->DeleteAndReplaceWith(check->ActualValue());
} else if (data->BasicBlock() == bb) {
// TODO(jkummerow): I think the following logic would be preferable:
// if (data->Basicblock() == bb ||
// graph()->use_optimistic_licm() ||
// bb->IsLoopSuccessorDominator()) {
// data->CoverCheck(check, offset)
// } else {
// /* add pristine BCBbData like in (data == NULL) case above */
// }
// Even better would be: distinguish between read-only dominator-imposed
// knowledge and modifiable upper/lower checks.
// What happens currently is that the first bounds check in a dominated
// block will stay around while any further checks are hoisted out,
// which doesn't make sense. Investigate/fix this in a future CL.
data->CoverCheck(check, offset);
} else if (graph()->use_optimistic_licm() ||
bb->IsLoopSuccessorDominator()) {
@ -411,6 +446,10 @@ BoundsCheckBbData* HBoundsCheckEliminationPhase::PreProcessBlock(
data->UpperCheck(),
bb_data_list,
data);
if (FLAG_trace_bce) {
OS::Print("Updated bounds check data for block #%d: [%d - %d]\n",
bb->block_id(), new_lower_offset, new_upper_offset);
}
table_.Insert(key, bb_data_list, zone());
}
}