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LowerSwitch: Fix producing invalid IR on unreachable code 

If a switch was in an unreachable block that branched
to a block with a phi, it would leave phis with missing
predecessors.

llvm-svn: 301064
This commit is contained in:
Matt Arsenault 2017-04-21 23:54:12 +00:00
parent 8150355498
commit 01d17e7c5f
2 changed files with 48 additions and 0 deletions
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8
llvm/lib/Transforms/Utils/LowerSwitch.cpp
View File

@ -403,6 +403,14 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI,
Value *Val = SI->getCondition(); // The value we are switching on...
BasicBlock* Default = SI->getDefaultDest();
// Don't handle unreachable blocks. If there are successors with phis, this
// would leave them behind with missing predecessors.
if ((CurBlock != &F->getEntryBlock() && pred_empty(CurBlock)) ||
CurBlock->getSinglePredecessor() == CurBlock) {
DeleteList.insert(CurBlock);
return;
}
// If there is only the default destination, just branch.
if (!SI->getNumCases()) {
BranchInst::Create(Default, CurBlock);

40
llvm/test/Transforms/LowerSwitch/phi-in-dead-block.ll Normal file
View File

@ -0,0 +1,40 @@
; RUN: opt -S -lowerswitch %s | FileCheck %s
; CHECK-LABEL: @phi_in_dead_block(
; CHECK-NOT: switch
define void @phi_in_dead_block() {
bb:
br i1 undef, label %bb2, label %bb3
bb1: ; No predecessors!
switch i32 undef, label %bb2 [
i32 9, label %bb3
]
bb2: ; preds = %bb1, %bb
%tmp = phi i64 [ undef, %bb1 ], [ undef, %bb ]
unreachable
bb3: ; preds = %bb1, %bb
unreachable
}
; CHECK-LABEL: @phi_in_dead_block_br_to_self(
; CHECK-NOT: switch
define void @phi_in_dead_block_br_to_self() {
bb:
br i1 undef, label %bb2, label %bb3
bb1: ; No predecessors!
switch i32 undef, label %bb2 [
i32 9, label %bb3
i32 10, label %bb1
]
bb2: ; preds = %bb1, %bb
%tmp = phi i64 [ undef, %bb1 ], [ undef, %bb ]
unreachable
bb3: ; preds = %bb1, %bb
unreachable
}