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Give uses within a loop a greater weight when doing representation inference.

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Uses of a value are weighted by a factor of FLAG_loop_weight (default: 10) for
every loop they are in. This makes uses in inner loops "more important", which
should improve the result of the representation inference.

Review URL: https://chromiumcodereview.appspot.com/8277031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10573 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
svenpanne@chromium.org 2012-02-01 08:49:18 +00:00
parent b2ead52688
commit 82d1f51534
4 changed files with 12 additions and 2 deletions
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1
src/flag-definitions.h
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@ -166,6 +166,7 @@ DEFINE_bool(use_osr, true, "use on-stack replacement")
DEFINE_bool(trace_osr, false, "trace on-stack replacement")
DEFINE_int(stress_runs, 0, "number of stress runs")
DEFINE_bool(optimize_closures, true, "optimize closures")
DEFINE_int(loop_weight, 1, "loop weight for representation inference")
// assembler-ia32.cc / assembler-arm.cc / assembler-x64.cc
DEFINE_bool(debug_code, false,

10
src/hydrogen-instructions.cc
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@ -67,6 +67,14 @@ const char* Representation::Mnemonic() const {
}
int HValue::LoopWeight() const {
const int w = FLAG_loop_weight;
static const int weights[] = { 1, w, w*w, w*w*w, w*w*w*w };
return weights[Min(block()->LoopNestingDepth(),
static_cast<int>(ARRAY_SIZE(weights)-1))];
}
void HValue::AssumeRepresentation(Representation r) {
if (CheckFlag(kFlexibleRepresentation)) {
ChangeRepresentation(r);
@ -1139,7 +1147,7 @@ void HPhi::InitRealUses(int phi_id) {
HValue* value = it.value();
if (!value->IsPhi()) {
Representation rep = value->RequiredInputRepresentation(it.index());
++non_phi_uses_[rep.kind()];
non_phi_uses_[rep.kind()] += value->LoopWeight();
}
}
}

1
src/hydrogen-instructions.h
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@ -569,6 +569,7 @@ class HValue: public ZoneObject {
HBasicBlock* block() const { return block_; }
void SetBlock(HBasicBlock* block);
int LoopWeight() const;
int id() const { return id_; }
void set_id(int id) { id_ = id; }

2
src/hydrogen.cc
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@ -1672,7 +1672,7 @@ Representation HInferRepresentation::TryChange(HValue* value) {
Representation rep = use->RequiredInputRepresentation(it.index());
if (rep.IsNone()) continue;
if (use->IsPhi()) HPhi::cast(use)->AddIndirectUsesTo(&use_count[0]);
++use_count[rep.kind()];
use_count[rep.kind()] += use->LoopWeight();
}
int tagged_count = use_count[Representation::kTagged];
int double_count = use_count[Representation::kDouble];