From: Daniel Berlin <dberlin@dberlin.org>
Date: Wed, 8 Feb 2017 02:48:25 +0000 (+0000)
Subject: Revert "CVP: Make CVP iterate in an order that maximizes reuse of LVI cache"
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=75bd1d7575dc7299dd5714588e2ca2b4d5658878;p=llvm

Revert "CVP: Make CVP iterate in an order that maximizes reuse of LVI cache"

This reverts commit r294398, it seems to be failing on the bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294399 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index f623b81df3a..60786a3373f 100644
--- a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -481,11 +481,12 @@ static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
 static bool runImpl(Function &F, LazyValueInfo *LVI) {
   bool FnChanged = false;
 
-  // Visiting in an inverse depth first traversal maximizes reuse of the LVI
-  // cache, as it currently iterates in depth first order upwards, caching
-  // overdefined info as it goes.
-
-  for (BasicBlock *BB : inverse_depth_first(&F.getEntryBlock())) {
+  // Visiting in a pre-order depth-first traversal causes us to simplify early
+  // blocks before querying later blocks (which require us to analyze early
+  // blocks).  Eagerly simplifying shallow blocks means there is strictly less
+  // work to do for deep blocks.  This also means we don't visit unreachable
+  // blocks. 
+  for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
     bool BBChanged = false;
     for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
       Instruction *II = &*BI++;