Revision: 8997
Author: [email protected]
Date: Tue Aug 23 04:19:08 2011
Log: Perform range analysis after GVN.
This eliminate redundant HChange instructions and allows range information
of
converted values propagated across control-flow splits.
It fixes the performance regression on code like:
if (x > 1) {
y = x - 1;
}
where we should eliminate the overflow check on the sub inside the
if-statement.
Review URL: http://codereview.chromium.org/7709025
http://code.google.com/p/v8/source/detail?r=8997
Modified:
/branches/bleeding_edge/src/hydrogen.cc
=======================================
--- /branches/bleeding_edge/src/hydrogen.cc Tue Aug 23 00:34:45 2011
+++ /branches/bleeding_edge/src/hydrogen.cc Tue Aug 23 04:19:08 2011
@@ -2328,17 +2328,8 @@
graph()->MarkDeoptimizeOnUndefined();
graph()->InsertRepresentationChanges();
- if (FLAG_use_range) {
- HRangeAnalysis rangeAnalysis(graph());
- rangeAnalysis.Analyze();
- }
graph()->InitializeInferredTypes();
graph()->Canonicalize();
- graph()->ComputeMinusZeroChecks();
-
- // Eliminate redundant stack checks on backwards branches.
- HStackCheckEliminator sce(graph());
- sce.Process();
// Perform common subexpression elimination and loop-invariant code
motion.
if (FLAG_use_gvn) {
@@ -2347,6 +2338,16 @@
gvn.Analyze();
}
+ if (FLAG_use_range) {
+ HRangeAnalysis rangeAnalysis(graph());
+ rangeAnalysis.Analyze();
+ }
+ graph()->ComputeMinusZeroChecks();
+
+ // Eliminate redundant stack checks on backwards branches.
+ HStackCheckEliminator sce(graph());
+ sce.Process();
+
// Replace the results of check instructions with the original value, if
the
// result is used. This is safe now, since we don't do code motion after
this
// point. It enables better register allocation since the value produced
by
--
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