[llvm] r352170 - [LoopSimplifyCFG] Fix inconsistency in blocks in loop markup

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Thu Jan 24 21:05:02 2019
New Revision: 352170

URL: http://llvm.org/viewvc/llvm-project?rev=352170&view=rev
Log:
[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	

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
    llvm/trunk/test/Transforms/LoopSimplifyCFG/live_block_marking.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=352170&r1=352169&r2=352170&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Thu Jan 24 21:05:02 2019
@@ -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.

Modified: llvm/trunk/test/Transforms/LoopSimplifyCFG/live_block_marking.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopSimplifyCFG/live_block_marking.ll?rev=352170&r1=352169&r2=352170&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopSimplifyCFG/live_block_marking.ll (original)
+++ llvm/trunk/test/Transforms/LoopSimplifyCFG/live_block_marking.ll Thu Jan 24 21:05:02 2019
@@ -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
 ;