[PATCH] D31753: [LoopPeeling] Fix condition for phi-eliminating

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 94362.
mkazantsev retitled this revision from "[LoopPeeling] Fix loop size check for non-forced invariant-based peeling" to "[LoopPeeling] Fix condition for phi-eliminating ".
mkazantsev edited the summary of this revision.

https://reviews.llvm.org/D31753

Files:
  lib/Transforms/Utils/LoopUnrollPeel.cpp
  test/Transforms/LoopUnroll/peel-loop-not-forced.ll


Index: test/Transforms/LoopUnroll/peel-loop-not-forced.ll
===================================================================
--- test/Transforms/LoopUnroll/peel-loop-not-forced.ll
+++ test/Transforms/LoopUnroll/peel-loop-not-forced.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -S -loop-unroll -unroll-threshold=4 | FileCheck %s
+; RUN: opt < %s -S -loop-unroll -unroll-threshold=8 | FileCheck %s
 
 define i32 @invariant_backedge_1(i32 %a, i32 %b) {
 ; CHECK-LABEL: @invariant_backedge_1
Index: lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -82,7 +82,8 @@
   // its only back edge. If there is such Phi, peeling 1 iteration from the
   // loop is profitable, because starting from 2nd iteration we will have an
   // invariant instead of this Phi.
-  if (LoopSize <= UP.Threshold) {
+  // First, check that we can peel at least one iteration.
+  if (2 * LoopSize <= UP.Threshold && UnrollPeelMaxCount > 0) {
     BasicBlock *BackEdge = L->getLoopLatch();
     assert(BackEdge && "Loop is not in simplified form?");
     BasicBlock *Header = L->getHeader();


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