Reviewers: Jakob,
Message:
PTAL
Description:
Load elimination fix: load should not be replaced with another load if the
former is not dominated by the latter.
Please review this at https://codereview.chromium.org/151333003/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+32, -1 lines):
M src/hydrogen-load-elimination.cc
M src/hydrogen.h
M src/hydrogen.cc
M test/mjsunit/compiler/load-elimination.js
Index: src/hydrogen-load-elimination.cc
diff --git a/src/hydrogen-load-elimination.cc
b/src/hydrogen-load-elimination.cc
index
ea12df865d7b0d91a43eb6f7162374e538509afb..634d75d8620f5ec866048f9794b8e2ff87a5a0a2
100644
--- a/src/hydrogen-load-elimination.cc
+++ b/src/hydrogen-load-elimination.cc
@@ -203,9 +203,12 @@ class HLoadEliminationTable : public ZoneObject {
// Load is not redundant. Fill out a new entry.
approx->last_value_ = instr;
return instr;
- } else {
+ } else if (approx->last_value_->block()->EqualToOrDominates(
+ instr->block())) {
// Eliminate the load. Reuse previously stored value or load
instruction.
return approx->last_value_;
+ } else {
+ return instr;
}
}
Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index
3c7bf5064b1683c2c8609a52ff6057d5eadda29d..9b511992489705367a04cf2372321c40bd8fb6fe
100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -302,6 +302,12 @@ bool HBasicBlock::Dominates(HBasicBlock* other) const {
}
+bool HBasicBlock::EqualToOrDominates(HBasicBlock* other) const {
+ if (this == other) return true;
+ return Dominates(other);
+}
+
+
int HBasicBlock::LoopNestingDepth() const {
const HBasicBlock* current = this;
int result = (current->IsLoopHeader()) ? 1 : 0;
Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index
a9c0d3204aff09ce3005e2006b61337e29366742..d863e3d11643d892874e9dd261f36c6589b44957
100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -112,6 +112,7 @@ class HBasicBlock V8_FINAL : public ZoneObject {
void RemovePhi(HPhi* phi);
void AddInstruction(HInstruction* instr, int position);
bool Dominates(HBasicBlock* other) const;
+ bool EqualToOrDominates(HBasicBlock* other) const;
int LoopNestingDepth() const;
void SetInitialEnvironment(HEnvironment* env);
Index: test/mjsunit/compiler/load-elimination.js
diff --git a/test/mjsunit/compiler/load-elimination.js
b/test/mjsunit/compiler/load-elimination.js
index
e6a82451821288e5a4665764e6e8b88b7387f72f..9bf8564308218e05973accbe1015a00eb46eae5d
100644
--- a/test/mjsunit/compiler/load-elimination.js
+++ b/test/mjsunit/compiler/load-elimination.js
@@ -43,6 +43,26 @@ function test_load() {
return a.x + a.x + a.x + a.x;
}
+
+function test_load_from_different_contexts() {
+ var r = 1;
+ this.f = function() {
+ var fr = r;
+ this.g = function(flag) {
+ var gr;
+ if (flag) {
+ gr = r;
+ } else {
+ gr = r;
+ }
+ return gr + r + fr;
+ };
+ };
+ this.f();
+ return this.g(true);
+}
+
+
function test_store_load() {
var a = new B(1, 2);
a.x = 4;
@@ -128,6 +148,7 @@ function test(x, f) {
}
test(4, test_load);
+test(3, new test_load_from_different_contexts().g);
test(22, test_store_load);
test(8, test_nonaliasing_store1);
test(5, test_transitioning_store1);
--
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