[PATCH] D154064: [InstructionSimplify] Limit threadCmpOverPHI recursion depth to 1

[Dhruv Chawla via Phabricator via llvm-commits]

0xdc03 created this revision.
0xdc03 added a reviewer: nikic.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
0xdc03 requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Other places in the compiler (such as ValueTracking) only allow
recursing one level into phi nodes, however in InstructionSimplify the
limit is 3.

By reducing it to 1, there is a slight reduction in compile times (0.1%):
https://llvm-compile-time-tracker.com/compare.php?from=47a4331cd79ff63b13e369e28ccca268773cf9f2&to=20d987ab937caf22929f0c5790f0a8197b53b447&stat=instructions:u


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D154064

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp


Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4011,7 +4011,8 @@
   // If the comparison is with the result of a phi instruction, check whether
   // doing the compare with each incoming phi value yields a common result.
   if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
-    if (Value *V = threadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse))
+    if (Value *V = threadCmpOverPHI(Pred, LHS, RHS, Q,
+                                    MaxRecurse > 1 ? 1 : MaxRecurse))
       return V;
 
   return nullptr;
@@ -4232,7 +4233,8 @@
   // If the comparison is with the result of a phi instruction, check whether
   // doing the compare with each incoming phi value yields a common result.
   if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
-    if (Value *V = threadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse))
+    if (Value *V = threadCmpOverPHI(Pred, LHS, RHS, Q,
+                                    MaxRecurse > 1 ? 1 : MaxRecurse))
       return V;
 
   return nullptr;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D154064.535720.patch
Type: text/x-patch
Size: 1127 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230629/623fd865/attachment.bin>