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[LoopSimplifyCFG] Fix inconsistency in blocks in loop markup

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2nd part of D57095 with the same reason, just in another place. We never
fold branches that are not immediately in the current loop, but this check
is missing in `IsEdgeLive` As result, it may think that the edge in subloop is
dead while it's live. It's a pessimization in the current stance.

Differential Revision: https://reviews.llvm.org/D57147
Reviewed By: rupprecht	

llvm-svn: 352170
This commit is contained in:
Max Kazantsev 2019-01-25 05:05:02 +00:00
parent b821e9787f
commit fe1793aa58
2 changed files with 6 additions and 4 deletions
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2
lib/Transforms/Scalar/LoopSimplifyCFG.cpp
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@ -239,7 +239,7 @@ private:
if (!LiveLoopBlocks.count(From))
return false;
BasicBlock *TheOnlySucc = getOnlyLiveSuccessor(From);
return !TheOnlySucc || TheOnlySucc == To;
return !TheOnlySucc || TheOnlySucc == To || LI.getLoopFor(From) != &L;
};
// The loop will not be destroyed if its latch is live.

8
test/Transforms/LoopSimplifyCFG/live_block_marking.ll
View File

@ -4,11 +4,13 @@
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(indvars,simplify-cfg)' -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -indvars -loop-simplifycfg -enable-mssa-loop-dependency=true -verify-memoryssa -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
; This test demonstrates a bug in live blocks markup that is only catchable in
; inter-pass interaction.
define void @test(i1 %c) {
; CHECK-LABEL: @test(
; CHECK-NEXT: entry:
; CHECK-NEXT: switch i32 0, label [[ENTRY_SPLIT:%.*]] [
; CHECK-NEXT: i32 1, label [[DEAD_EXIT:%.*]]
; CHECK-NEXT: ]
; CHECK: entry-split:
; CHECK-NEXT: br label [[OUTER:%.*]]
; CHECK: outer:
; CHECK-NEXT: br i1 [[C:%.*]], label [[TO_FOLD:%.*]], label [[LATCH:%.*]]
@ -25,7 +27,7 @@ define void @test(i1 %c) {
; CHECK: latch.loopexit:
; CHECK-NEXT: br label [[LATCH]]
; CHECK: latch:
; CHECK-NEXT: br i1 true, label [[OUTER]], label [[DEAD_EXIT:%.*]]
; CHECK-NEXT: br label [[OUTER]]
; CHECK: dead_exit:
; CHECK-NEXT: ret void
;