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[LoopSimplifyCFG] Fix inconsistency in blocks in loop markup 

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 299d690a50
commit 38cd9acbb9
2 changed files with 6 additions and 4 deletions
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2
llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
View File

@ -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
llvm/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
;