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[Attributor][NFC] Do not delete dead blocks but "clear" them 

Deleting blocks will require us to deal with dead edges, e.g.,
  `br i1 false, label %live, label %dead`
explicitly. For now we just clear the blocks and move on.
This will be revisited once we actually fold branches.
This commit is contained in:
Johannes Doerfert 2019-10-30 17:34:59 -05:00
parent fe799c97fa
commit 5e442a51bc
2 changed files with 6 additions and 6 deletions
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9
llvm/lib/Transforms/IPO/Attributor.cpp
View File

@ -4644,9 +4644,12 @@ ChangeStatus Attributor::run(Module &M) {
SmallVector<BasicBlock *, 8> ToBeDeletedBBs;
ToBeDeletedBBs.reserve(NumDeadBlocks);
ToBeDeletedBBs.append(ToBeDeletedBlocks.begin(), ToBeDeletedBlocks.end());
DeleteDeadBlocks(ToBeDeletedBBs);
STATS_DECLTRACK(AAIsDead, BasicBlock,
"Number of dead basic blocks deleted.");
// Actually we do not delete the blocks but squash them into a single
// unreachable but untangling branches that jump here is something we need
// to do in a more generic way.
DetatchDeadBlocks(ToBeDeletedBBs, nullptr);
STATS_DECL(AAIsDead, BasicBlock, "Number of dead basic blocks deleted.");
BUILD_STAT_NAME(AAIsDead, BasicBlock) += ToBeDeletedBlocks.size();
}
STATS_DECL(AAIsDead, Function, "Number of dead functions deleted.");

3
llvm/test/Transforms/FunctionAttrs/liveness.ll
View File

@ -56,7 +56,6 @@ entry:
call void @no_return_call()
; CHECK: call void @no_return_call()
; CHECK-NEXT: unreachable
; CHECK-NEXT: }
call i32 @dead_internal_func(i32 10)
%cmp = icmp eq i32 %a, 0
br i1 %cmp, label %cond.true, label %cond.false
@ -130,7 +129,6 @@ cond.false: ; preds = %entry
; CHECK: call void @no_return_call()
; CHECK-NEXT: unreachable
call i32 @dead_internal_func(i32 10)
; CHECK-NEXT: }
%call1 = call i32 @bar()
br label %cond.end
@ -526,7 +524,6 @@ define linkonce_odr void @non_exact3() {
; CHECK-NEXT: call void @non_dead_d15()
; CHECK-NEXT: %nr = call i32 @foo_noreturn()
; CHECK-NEXT: unreachable
; CHECK-NEXT: }
define internal void @non_dead_a0() { ret void }
define internal void @non_dead_a1() { ret void }