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[SimpleLoopUnswitch] After unswitch delete dead blocks in parent loops 

Summary:
Assert from PR38737 happens on the dead block inside the parent loop
after unswitching nontrivial switch in the inner loop.

deleteDeadBlocksFromLoop now takes extra care to detect/remove dead
blocks in all the parent loops in addition to the blocks from original
loop being unswitched.

Reviewers: asbirlea, chandlerc

Reviewed By: asbirlea

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D51415

llvm-svn: 340955
This commit is contained in:
Fedor Sergeev 2018-08-29 19:10:44 +00:00
parent cf311cfc20
commit 7b49aa03af
2 changed files with 55 additions and 2 deletions
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12
llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
View File

@ -1380,13 +1380,21 @@ deleteDeadBlocksFromLoop(Loop &L,
DominatorTree &DT, LoopInfo &LI) {
// Find all the dead blocks, and remove them from their successors.
SmallVector<BasicBlock *, 16> DeadBlocks;
for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks))
for (BasicBlock *BB : ExitBlocks)
if (!DT.isReachableFromEntry(BB)) {
for (BasicBlock *SuccBB : successors(BB))
SuccBB->removePredecessor(BB);
DeadBlocks.push_back(BB);
}
for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop())
for (BasicBlock *BB : ParentL->blocks())
if (!DT.isReachableFromEntry(BB)) {
for (BasicBlock *SuccBB : successors(BB))
SuccBB->removePredecessor(BB);
DeadBlocks.push_back(BB);
}
SmallPtrSet<BasicBlock *, 16> DeadBlockSet(DeadBlocks.begin(),
DeadBlocks.end());
@ -1431,7 +1439,7 @@ deleteDeadBlocksFromLoop(Loop &L,
// Actually delete the blocks now that they've been fully unhooked from the
// IR.
for (auto *BB : DeadBlocks)
for (auto *BB : DeadBlockSet)
BB->eraseFromParent();
}

45
llvm/test/Transforms/SimpleLoopUnswitch/delete-dead-blocks.ll Normal file
View File

@ -0,0 +1,45 @@
; RUN: opt < %s -simple-loop-unswitch -enable-nontrivial-unswitch -S 2>&1 | FileCheck %s
; RUN: opt < %s -passes=unswitch -enable-nontrivial-unswitch -S 2>&1 | FileCheck %s
;
; Checking that (dead) blocks from inner loop are deleted after unswitch.
;
declare void @foo()
; CHECK-LABEL: @Test
define void @Test(i32) {
entry:
br label %outer
outer:
%oi = phi i32 [ 0, %entry ], [ %oinc, %outer_continue]
br label %inner
inner:
%ii = phi i32 [ 0, %outer ], [ %iinc, %continue]
call void @foo()
switch i32 %0, label %get_out2 [
i32 0, label %continue
i32 1, label %case1
i32 2, label %get_out
]
;
; since we unswitch on the above switch, %case1 and %continue blocks
; become dead in the original loop
;
; CHECK-NOT: case1:
case1:
br label %continue
; CHECK-NOT: {{^}}continue:
continue:
%iinc = add i32 %ii, 1
%icmp = icmp eq i32 %ii, 100
br i1 %icmp, label %inner, label %outer_continue
outer_continue:
%oinc = add i32 %oi, 1
%ocmp = icmp eq i32 %oi, 100
br i1 %ocmp, label %outer, label %get_out
get_out:
ret void
get_out2:
unreachable
}