Improved and simplified loop optimizations.
Rationale:
This CL merges some common cases into one, thereby simplifying
the code quite a bit. It also prepares for more general induction
cycles (rather than the simple phi-add currently used). Finally,
it generalizes the closed form elimination with empty loops.
As a result of the latter, elaborate but weird code like:
private static int waterFall() {
int i = 0;
for (; i < 10; i++);
for (; i < 20; i++);
for (; i < 30; i++);
for (; i < 40; i++);
for (; i < 50; i++);
return i;
}
now becomes just this (on x86)!
mov eax, 50
ret
Change-Id: I8d22ce63ce9696918f57bb90f64d9a9303a4791d
Test: m test-art-host
diff --git a/compiler/optimizing/loop_optimization.h b/compiler/optimizing/loop_optimization.h
index 6092955..b2bf1c8 100644
--- a/compiler/optimizing/loop_optimization.h
+++ b/compiler/optimizing/loop_optimization.h
@@ -63,9 +63,13 @@
void SimplifyInduction(LoopNode* node);
void RemoveIfEmptyLoop(LoopNode* node);
- void ReplaceAllUses(HInstruction* instruction,
- HInstruction* replacement,
- HInstruction* exclusion);
+ bool IsOnlyUsedAfterLoop(const HLoopInformation& loop_info,
+ HInstruction* instruction,
+ /*out*/ int32_t* use_count);
+ void ReplaceAllUses(HInstruction* instruction, HInstruction* replacement);
+ bool TryReplaceWithLastValue(HInstruction* instruction,
+ int32_t use_count,
+ HBasicBlock* block);
// Range information based on prior induction variable analysis.
InductionVarRange induction_range_;
@@ -79,6 +83,10 @@
LoopNode* top_loop_;
LoopNode* last_loop_;
+ // Temporary bookkeeping of a set of instructions.
+ // Contents reside in phase-local heap memory.
+ ArenaSet<HInstruction*>* iset_;
+
friend class LoopOptimizationTest;
DISALLOW_COPY_AND_ASSIGN(HLoopOptimization);