From: fschneider@chromium.org <fschneider@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Tue, 23 Aug 2011 11:19:08 +0000 (+0000)
Subject: Perform range analysis after GVN.
X-Git-Tag: upstream/4.7.83~18665
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=701146a3d72589594291f0a5be2bba39d058c0b6;p=platform%2Fupstream%2Fv8.git

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

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8997 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---

diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 3a6849d2b..d321aacb0 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -2328,17 +2328,8 @@ HGraph* HGraphBuilder::CreateGraph() {
   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 @@ HGraph* HGraphBuilder::CreateGraph() {
     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