RPCSX/llvm
1
0
Fork 0
mirror of https://github.com/RPCSX/llvm.git synced 2024-12-01 07:30:31 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

[LoopUnroll] Fix the way we update DT after complete unrolling.

Browse Source 
Updating dominators for exit-blocks of the unrolled loops is not enough,
as shown in PR27157. The proper way is to update dominators for all
dominance-children of original loop blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265605 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Zolotukhin 2016-04-06 21:47:12 +00:00
parent d50171b8c7
commit 243a05e2ed
2 changed files with 68 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
lib/Transforms/Utils/LoopUnroll.cpp
View File

@ -262,6 +262,7 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
bool CompletelyUnroll = Count == TripCount;
SmallVector<BasicBlock *, 4> ExitBlocks;
L->getExitBlocks(ExitBlocks);
std::vector<BasicBlock*> OriginalLoopBlocks = L->getBlocks();
// Go through all exits of L and see if there are any phi-nodes there. We just
// conservatively assume that they're inserted to preserve LCSSA form, which
@ -551,20 +552,24 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
Term->eraseFromParent();
}
}
// Update dominators of loop exit blocks.
// Immediate dominator of an exit block might change, because we add more
// Update dominators of blocks we might reach through exits.
// Immediate dominator of such block might change, because we add more
// routes which can lead to the exit: we can now reach it from the copied
// iterations too. Thus, the new idom of the exit block will be the nearest
// iterations too. Thus, the new idom of the block will be the nearest
// common dominator of the previous idom and common dominator of all copies of
// the exiting block. This is equivalent to the nearest common dominator of
// the previous idom. This is equivalent to the nearest common dominator of
// the previous idom and the first latch, which dominates all copies of the
// exiting block.
// previous idom.
if (DT && Count > 1) {
for (auto Exit : ExitBlocks) {
BasicBlock *PrevIDom = DT->getNode(Exit)->getIDom()->getBlock();
BasicBlock *NewIDom =
DT->findNearestCommonDominator(PrevIDom, Latches[0]);
DT->changeImmediateDominator(Exit, NewIDom);
for (auto *BB : OriginalLoopBlocks) {
auto *BBDomNode = DT->getNode(BB);
for (auto *ChildDomNode : BBDomNode->getChildren()) {
auto *ChildBB = ChildDomNode->getBlock();
if (L->contains(ChildBB))
continue;
BasicBlock *NewIDom = DT->findNearestCommonDominator(BB, Latches[0]);
DT->changeImmediateDominator(ChildBB, NewIDom);
}
}
}

53
test/Transforms/LoopUnroll/pr27157.ll Normal file
View File

@ -0,0 +1,53 @@
; RUN: opt -loop-unroll -debug-only=loop-unroll -disable-output < %s
; REQUIRES: asserts
; Compile this test with debug flag on to verify domtree right after loop unrolling.
target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
; PR27157
define void @foo() {
entry:
br label %loop_header
loop_header:
%iv = phi i64 [ 0, %entry ], [ %iv_next, %loop_latch ]
br i1 undef, label %loop_latch, label %loop_exiting_bb1
loop_exiting_bb1:
br i1 false, label %loop_exiting_bb2, label %exit1.loopexit
loop_exiting_bb2:
br i1 false, label %loop_latch, label %bb
bb:
br label %exit1
loop_latch:
%iv_next = add nuw nsw i64 %iv, 1
%cmp = icmp ne i64 %iv_next, 2
br i1 %cmp, label %loop_header, label %exit2
exit1.loopexit:
br label %exit1
exit1:
ret void
exit2:
ret void
}
define void @foo2() {
entry:
br label %loop.header
loop.header:
%iv = phi i32 [ 0, %entry ], [ %iv.inc, %latch ]
%iv.inc = add i32 %iv, 1
br i1 undef, label %diamond, label %latch
diamond:
br i1 undef, label %left, label %right
left:
br i1 undef, label %exit, label %merge
right:
br i1 undef, label %exit, label %merge
merge:
br label %latch
latch:
%end.cond = icmp eq i32 %iv, 1
br i1 %end.cond, label %exit1, label %loop.header
exit:
ret void
exit1:
ret void
}