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LoopUnroll: Create sub-loops in LoopInfo

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`LoopUnrollPass` says that it preserves `LoopInfo` -- make it so.  In
particular, tell `LoopInfo` about copies of inner loops when unrolling
the outer loop.

Conservatively, also tell `ScalarEvolution` to forget about the original
versions of these loops, since their inputs may have changed.

Fixes PR20987.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219241 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2014-10-07 21:19:00 +00:00
parent 25cfb5cff5
commit de7465af34
2 changed files with 64 additions and 1 deletions
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30
lib/Transforms/Utils/LoopUnroll.cpp
View File

@ -301,13 +301,41 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
for (unsigned It = 1; It != Count; ++It) {
std::vector<BasicBlock*> NewBlocks;
SmallDenseMap<const Loop *, Loop *, 4> NewLoops;
NewLoops[L] = L;
for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
ValueToValueMapTy VMap;
BasicBlock *New = CloneBasicBlock(*BB, VMap, "." + Twine(It));
Header->getParent()->getBasicBlockList().push_back(New);
L->addBasicBlockToLoop(New, LI->getBase());
// Tell LI about New.
if (*BB == Header) {
assert(LI->getLoopFor(*BB) == L && "Header should not be in a sub-loop");
L->addBasicBlockToLoop(New, LI->getBase());
} else {
// Figure out which loop New is in.
const Loop *OldLoop = LI->getLoopFor(*BB);
assert(OldLoop && "Should (at least) be in the loop being unrolled!");
Loop *&NewLoop = NewLoops[OldLoop];
if (!NewLoop) {
// Found a new sub-loop.
assert(*BB == OldLoop->getHeader() &&
"Header should be first in RPO");
Loop *NewLoopParent = NewLoops.lookup(OldLoop->getParentLoop());
assert(NewLoopParent &&
"Expected parent loop before sub-loop in RPO");
NewLoop = new Loop;
NewLoopParent->addChildLoop(NewLoop);
// Forget the old loop, since its inputs may have changed.
if (SE)
SE->forgetLoop(OldLoop);
}
NewLoop->addBasicBlockToLoop(New, LI->getBase());
}
if (*BB == Header)
// Loop over all of the PHI nodes in the block, changing them to use

35
test/Transforms/LoopUnroll/update-loop-info-in-subloops.ll Normal file
View File

@ -0,0 +1,35 @@
; RUN: opt -S < %s -loop-unroll -block-freq | FileCheck %s
; Crasher from PR20987.
; CHECK: define void @update_loop_info_in_subloops
; CHECK: entry:
; CHECK: L:
; CHECK: L.inner:
; CHECK: L.inner.latch:
; CHECK: L.latch:
; CHECK: L.inner.1:
; CHECK: L.inner.latch.1:
; CHECK: L.latch.1:
define void @update_loop_info_in_subloops() {
entry:
br label %L
L:
%0 = phi i64 [ 1, %entry ], [ %1, %L.latch ]
br label %L.inner
L.inner:
br label %L.inner.latch
L.inner.latch:
br i1 false, label %L.latch, label %L.inner
L.latch:
%1 = add i64 %0, 1
%2 = icmp eq i64 %1, 3
br i1 %2, label %exit, label %L
exit:
ret void
}