[llvm] r351433 - [LoopSimplifyCFG] Fix order of deletion of complex dead subloops

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Thu Jan 17 04:25:40 2019
New Revision: 351433

URL: http://llvm.org/viewvc/llvm-project?rev=351433&view=rev
Log:
[LoopSimplifyCFG] Fix order of deletion of complex dead subloops

Function `DeleteDeadBlock` requires that all predecessors of a block
being deleted have already been deleted, with the exception of a
single-block loop. When we use it for removal of dead subloops that
contain more than one block, we may not fulfull this requirement and
fail an assertion.

This patch replaces invocation of `DeleteDeadBlock` with a generalized
version `DeleteDeadBlocks` that is able to deal with multiple dead blocks,
even if they contain some cycles.

Differential Revision: https://reviews.llvm.org/D56121
Reviewed By: fedor.sergeev

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
    llvm/trunk/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=351433&r1=351432&r2=351433&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Thu Jan 17 04:25:40 2019
@@ -402,9 +402,10 @@ private:
         LI.erase(LI.getLoopFor(BB));
       }
       LI.removeBlock(BB);
-      DeleteDeadBlock(BB, &DTU);
-      ++NumLoopBlocksDeleted;
     }
+
+    DeleteDeadBlocks(DeadLoopBlocks, &DTU);
+    NumLoopBlocksDeleted += DeadLoopBlocks.size();
   }
 
   /// Constant-fold terminators of blocks acculumated in FoldCandidates into the

Modified: llvm/trunk/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll?rev=351433&r1=351432&r2=351433&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll (original)
+++ llvm/trunk/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll Thu Jan 17 04:25:40 2019
@@ -1,7 +1,4 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; XFAIL: *
-; Tests complex_dead_subloop_branch and complex_dead_subloop_switch fail an
-; assertion, therefore the CFG simplification is temporarily disabled.
 ; REQUIRES: asserts
 ; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -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 -passes='require<domtree>,loop(simplify-cfg)' -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
@@ -2512,6 +2509,15 @@ exit:
 }
 
 define i32 @complex_dead_subloop_branch(i1 %cond1, i1 %cond2, i1 %cond3) {
+; CHECK-LABEL: @complex_dead_subloop_branch(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    br i1 [[COND3:%.*]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT_LCSSA:%.*]] = phi i32 [ 0, [[LOOP]] ]
+; CHECK-NEXT:    ret i32 [[RESULT_LCSSA]]
+;
 entry:
   br label %loop
 
@@ -2540,6 +2546,15 @@ exit:
 }
 
 define i32 @complex_dead_subloop_switch(i1 %cond1, i1 %cond2, i1 %cond3) {
+; CHECK-LABEL: @complex_dead_subloop_switch(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    br i1 [[COND3:%.*]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT_LCSSA:%.*]] = phi i32 [ 0, [[LOOP]] ]
+; CHECK-NEXT:    ret i32 [[RESULT_LCSSA]]
+;
 entry:
   br label %loop