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[RuntimeLoopUnrolling] Rename exit block and move assert earlier. NFC

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The single exit block allowed in runtime unrolling is guaranteed to be
the Latch's successor, so rename it as LatchExitBlock.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306105 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anna Thomas 2017-06-23 14:28:01 +00:00
parent 6ae9f209aa
commit 5b66dfbd50
1 changed files with 23 additions and 23 deletions
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46
lib/Transforms/Utils/LoopUnrollRuntime.cpp
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@ -472,10 +472,22 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// exit block only.
if (!L->isLoopSimplifyForm())
return false;
BasicBlock *Exit = L->getUniqueExitBlock(); // successor out of loop
if (!Exit)
return false;
// Guaranteed by LoopSimplifyForm.
BasicBlock *Latch = L->getLoopLatch();
BasicBlock *LatchExit = L->getUniqueExitBlock(); // successor out of loop
if (!LatchExit)
return false;
// Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
// targets of the Latch be the single exit block out of the loop. This needs
// to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
assert((LatchBR->getSuccessor(0) == LatchExit ||
LatchBR->getSuccessor(1) == LatchExit) &&
"one of the loop latch successors should be "
"the exit block!");
(void)LatchBR;
// Use Scalar Evolution to compute the trip count. This allows more loops to
// be unrolled than relying on induction var simplification.
if (!SE)
@ -510,25 +522,13 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
if (Log2_32(Count) > BEWidth)
return false;
BasicBlock *Latch = L->getLoopLatch();
// Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
// targets of the Latch be the single exit block out of the loop. This needs
// to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
assert(
(LatchBR->getSuccessor(0) == Exit || LatchBR->getSuccessor(1) == Exit) &&
"one of the loop latch successors should be "
"the exit block!");
// Avoid warning of unused `LatchBR` variable in release builds.
(void)LatchBR;
// Loop structure is the following:
//
// PreHeader
// Header
// ...
// Latch
// Exit
// LatchExit
BasicBlock *NewPreHeader;
BasicBlock *NewExit = nullptr;
@ -541,9 +541,9 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// Split PreHeader to insert a branch around loop for unrolling.
NewPreHeader = SplitBlock(PreHeader, PreHeader->getTerminator(), DT, LI);
NewPreHeader->setName(PreHeader->getName() + ".new");
// Split Exit to create phi nodes from branch above.
SmallVector<BasicBlock*, 4> Preds(predecessors(Exit));
NewExit = SplitBlockPredecessors(Exit, Preds, ".unr-lcssa",
// Split LatchExit to create phi nodes from branch above.
SmallVector<BasicBlock*, 4> Preds(predecessors(LatchExit));
NewExit = SplitBlockPredecessors(LatchExit, Preds, ".unr-lcssa",
DT, LI, PreserveLCSSA);
// Split NewExit to insert epilog remainder loop.
EpilogPreHeader = SplitBlock(NewExit, NewExit->getTerminator(), DT, LI);
@ -570,7 +570,7 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// Latch Header
// *NewExit ...
// *EpilogPreHeader Latch
// Exit Exit
// LatchExit LatchExit
// Calculate conditions for branch around loop for unrolling
// in epilog case and around prolog remainder loop in prolog case.
@ -648,7 +648,7 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// Clone all the basic blocks in the loop. If Count is 2, we don't clone
// the loop, otherwise we create a cloned loop to execute the extra
// iterations. This function adds the appropriate CFG connections.
BasicBlock *InsertBot = UseEpilogRemainder ? Exit : PrologExit;
BasicBlock *InsertBot = UseEpilogRemainder ? LatchExit : PrologExit;
BasicBlock *InsertTop = UseEpilogRemainder ? EpilogPreHeader : PrologPreHeader;
CloneLoopBlocks(L, ModVal, CreateRemainderLoop, UseEpilogRemainder, InsertTop,
InsertBot, NewPreHeader, NewBlocks, LoopBlocks, VMap, DT, LI);
@ -672,7 +672,7 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// EpilogHeader Header
// ... ...
// EpilogLatch Latch
// Exit Exit
// LatchExit LatchExit
// Rewrite the cloned instruction operands to use the values created when the
// clone is created.
@ -686,7 +686,7 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
if (UseEpilogRemainder) {
// Connect the epilog code to the original loop and update the
// PHI functions.
ConnectEpilog(L, ModVal, NewExit, Exit, PreHeader,
ConnectEpilog(L, ModVal, NewExit, LatchExit, PreHeader,
EpilogPreHeader, NewPreHeader, VMap, DT, LI,
PreserveLCSSA);