[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351433 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index 2e5927f9a068939576167085aa1794f6edf817f7..d51e6005d684a67b58563e93704bccbde7b2646f 100644 (file)
--- a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -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

diff --git a/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll b/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
index db5f0f1f3f2ef77a9d8dd0cce74ca4e0ef857380..25d6f2bbdb24ba3f40c3717a03bbe19230647b67 100644 (file)
--- a/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
+++ b/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
@@ -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