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Revert r300657 due to crashes in stage2 of bootstraps: 

http://lab.llvm.org:8011/builders/clang-with-lto-ubuntu/builds/2476/steps/build-stage2-LLVMgold.so/logs/stdio
http://bb.pgr.jp/builders/clang-3stage-x86_64-linux/builds/15036/steps/build_llvmclang/logs/stdio

I've updated the commit thread, reverting to get the bots back to green.

Original commit summary:
[JumpThread] We want to fold (not thread) when all predecessor go to single BB's successor.

llvm-svn: 300662
This commit is contained in:
Chandler Carruth 2017-04-19 06:23:20 +00:00
parent 47d58ea681
commit ae3386aa74
2 changed files with 0 additions and 116 deletions
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27
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -1289,33 +1289,6 @@ bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
if (PredToDestList.empty())
return false;
// If all the predecessors go to a single known successor, we want to fold,
// not thread. By doing so, we do not need to duplicate the current block and
// also miss potential opportunities in case we don't/can't duplicate.
if (OnlyDest && OnlyDest != MultipleDestSentinel) {
if (PredToDestList.size() ==
(size_t)std::distance(pred_begin(BB), pred_end(BB))) {
for (BasicBlock *SuccBB : successors(BB)) {
if (SuccBB != OnlyDest)
SuccBB->removePredecessor(BB, true); // This is unreachable successor.
}
// Finally update the terminator.
TerminatorInst *Term = BB->getTerminator();
BranchInst::Create(OnlyDest, Term);
Term->eraseFromParent();
// If the condition is now dead due to the removal of the old terminator,
// erase it.
auto *CondInst = dyn_cast<Instruction>(Cond);
if (CondInst && CondInst->use_empty())
CondInst->eraseFromParent();
// FIXME: in case this instruction is defined in the current BB and it
// resolves to a single value from all predecessors, we can do RAUW.
return true;
}
}
// Determine which is the most common successor. If we have many inputs and
// this block is a switch, we want to start by threading the batch that goes
// to the most popular destination first. If we only know about one

89
llvm/test/Transforms/JumpThreading/basic.ll
View File

@ -4,95 +4,6 @@ declare i32 @f1()
declare i32 @f2()
declare void @f3()
; Make sure we can fold this branch ... We will not be able to thread it as
; L0 is too big to duplicate. L2 is the unreachable block here.
;
; CHECK-LABEL: @test_br_folding_not_threading(
; CHECK: L1:
; CHECK: call i32 @f2()
; CHECK: call void @f3()
; CHECK-NEXT: ret void
; CHECK-NOT: br
; CHECK: L3:
define void @test_br_folding_not_threading(i1 %cond) nounwind {
entry:
br i1 %cond, label %L0, label %L3
L0:
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
br i1 %cond, label %L1, label %L2
L1:
call void @f3()
ret void
L2:
call void @f3()
ret void
L3:
call void @f3()
ret void
}
; Make sure we can fold this branch ... We will not be able to thread it as
; L0 is too big to duplicate. L2 is the unreachable block here.
; With more than 1 predecessors.
;
; CHECK-LABEL: @test_br_folding_not_threading_multiple_preds(
; CHECK: L1:
; CHECK: call i32 @f2()
; CHECK: call void @f3()
; CHECK-NEXT: ret void
; CHECK-NOT: br
; CHECK: L3:
define void @test_br_folding_not_threading_multiple_preds(i1 %condx, i1 %cond) nounwind {
entry:
br i1 %condx, label %X0, label %X1
X0:
br i1 %cond, label %L0, label %L3
X1:
br i1 %cond, label %L0, label %L3
L0:
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
call i32 @f2()
br i1 %cond, label %L1, label %L2
L1:
call void @f3()
ret void
L2:
call void @f3()
ret void
L3:
call void @f3()
ret void
}
define i32 @test1(i1 %cond) {
; CHECK-LABEL: @test1(