[SimplifyCFG] When merging conditional stores, don't count the store we're merging...

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317368 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 3c4dae92ebf3e2371cf82bc8bd3eda1c2feb3429..e0045e9f48a4eab282e2fa87534094e3d50fa732 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2901,7 +2901,9 @@ static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
       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 &&

diff --git a/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll b/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
index a2b94038001689490c3fb6e54e1751140dac6103..a2ca63d0a2df97664f46fae7551c7f04d5405dd5 100644 (file)
--- a/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
+++ b/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
@@ -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"