[PATCH] D39570: [SimplifyCFG] When merging conditional stores, don't count the store we're merging against the PHINodeFoldingThreshold

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

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.


https://reviews.llvm.org/D39570

Files:
  lib/Transforms/Utils/SimplifyCFG.cpp
  test/Transforms/SimplifyCFG/merge-cond-stores-2.ll


Index: test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
===================================================================
--- test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
+++ 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"
Index: lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyCFG.cpp
+++ lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2901,7 +2901,9 @@
       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 &&


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D39570.121383.patch
Type: text/x-patch
Size: 1299 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20171102/3fda0f09/attachment.bin>