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[LoopSimplifyCFG] Delete landing pads in dead exit blocks

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In addition to removing phi nodes this patch removes any
landing pad that the dead exit block might have. Without
this fix Verifier complains about a new switch instruction
jumps to a block with a landing pad.

Differential Revision: https://reviews.llvm.org/D84320
This commit is contained in:
Yevgeny Rouban 2020-07-29 17:47:36 +07:00
parent 62153b67c4
commit a2a9ffd73d
2 changed files with 99 additions and 6 deletions
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17
lib/Transforms/Scalar/LoopSimplifyCFG.cpp
View File

@ -366,15 +366,20 @@ private:
unsigned DummyIdx = 1;
for (BasicBlock *BB : DeadExitBlocks) {
SmallVector<Instruction *, 4> DeadPhis;
// Eliminate all Phis and LandingPads from dead exits.
// TODO: Consider removing all instructions in this dead block.
SmallVector<Instruction *, 4> DeadInstructions;
for (auto &PN : BB->phis())
DeadPhis.push_back(&PN);
DeadInstructions.push_back(&PN);
// Eliminate all Phis from dead exits.
for (Instruction *PN : DeadPhis) {
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
if (auto *LandingPad = dyn_cast<LandingPadInst>(BB->getFirstNonPHI()))
DeadInstructions.emplace_back(LandingPad);
for (Instruction *I : DeadInstructions) {
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
assert(DummyIdx != 0 && "Too many dead exits!");
DummySwitch->addCase(Builder.getInt32(DummyIdx++), BB);
DTUpdates.push_back({DominatorTree::Insert, Preheader, BB});

88
test/Transforms/LoopSimplifyCFG/handle_dead_exits.ll Normal file
View File

@ -0,0 +1,88 @@
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(simplify-cfg)' %s | FileCheck %s
declare i32* @fake_personality_function()
declare void @foo()
define i32 @test_remove_lpad(i1 %exitcond) personality i32* ()* @fake_personality_function {
; CHECK-LABEL: @test_remove_lpad(
entry:
br label %for.body
for.body:
br i1 0, label %never, label %next
next:
br label %latch
latch:
br i1 %exitcond, label %exit, label %for.body
exit:
ret i32 0
never:
invoke void @foo() to label %next unwind label %never-unwind
never-unwind:
; CHECK: never-unwind:
; CHECK-NEXT: unreachable
%res = landingpad token cleanup
unreachable
}
define i32 @test_remove_phi_lpad(i1 %exitcond) personality i32* ()* @fake_personality_function {
; CHECK-LABEL: @test_remove_phi_lpad(
entry:
br label %for.body
for.body:
br i1 0, label %never, label %next
next:
br label %latch
latch:
br i1 %exitcond, label %exit, label %for.body
exit:
ret i32 0
never:
invoke void @foo() to label %next unwind label %never-unwind
never-unwind:
; CHECK: never-unwind:
; CHECK-NEXT: ret i32 undef
%p = phi i32 [1, %never]
%res = landingpad token cleanup
ret i32 %p
}
define i32 @test_split_remove_phi_lpad_(i1 %exitcond) personality i32* ()* @fake_personality_function {
; CHECK-LABEL: @test_split_remove_phi_lpad_(
entry:
invoke void @foo() to label %for.body unwind label %unwind-bb
for.body:
br i1 0, label %never, label %next
next:
br label %latch
latch:
br i1 %exitcond, label %exit, label %for.body
exit:
ret i32 0
never:
invoke void @foo() to label %next unwind label %unwind-bb
unwind-bb:
; CHECK: unwind-bb.loopexit:
; CHECK-NEXT: br label %unwind-bb
%p = phi i32 [1, %never], [2, %entry]
%res = landingpad token cleanup
ret i32 %p
}