[llvm] r317368 - [SimplifyCFG] When merging conditional stores, don't count the store we're merging against the PHINodeFoldingThreshold

[Craig Topper via llvm-commits]

Author: ctopper
Date: Fri Nov  3 14:08:13 2017
New Revision: 317368

URL: http://llvm.org/viewvc/llvm-project?rev=317368&view=rev
Log:
[SimplifyCFG] When merging conditional stores, don't count the store we're merging against the PHINodeFoldingThreshold

Merging conditional stores tries to check to see if the code is if convertible after the store is moved. But the store hasn't been moved yet so its being counted against the threshold.

The patch adds 1 to the threshold comparison to make sure we don't count the store. I've adjusted a test to use a lower threshold to ensure we still do that conversion with the lower threshold.

Differential Revision: https://reviews.llvm.org/D39570

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=317368&r1=317367&r2=317368&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Fri Nov  3 14:08:13 2017
@@ -2901,7 +2901,9 @@ static bool mergeConditionalStoreToAddre
       else
         return false;
     }
-    return N <= PHINodeFoldingThreshold;
+    // The store we want to merge is counted in N, so add 1 to make sure
+    // we're counting the instructions that would be left.
+    return N <= (PHINodeFoldingThreshold + 1);
   };
 
   if (!MergeCondStoresAggressively &&

Modified: llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll?rev=317368&r1=317367&r2=317368&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll Fri Nov  3 14:08:13 2017
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S < %s -simplifycfg -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=2 | FileCheck %s
+; RUN: opt -S < %s -simplifycfg -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=1 | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "armv7--linux-gnueabihf"