RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2025-02-06 02:29:51 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Bail on unswitching a switch statement for a case with a critical edge. We name

Browse Source 
which edge to split by pred/succ pair, which means that we can end up splitting
the wrong edge (by case value) in the switch statement entirely. Fixes PR10031!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132535 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-06-03 06:27:15 +00:00
parent 3d26f2333b
commit 444f297a78
2 changed files with 33 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -258,6 +258,7 @@ bool LoopUnswitch::processCurrentLoop() {
if (LoopCond && SI->getNumCases() > 1) {
// Find a value to unswitch on:
// FIXME: this should chose the most expensive case!
// FIXME: scan for a case with a non-critical edge?
Constant *UnswitchVal = SI->getCaseValue(1);
// Do not process same value again and again.
if (!UnswitchedVals.insert(UnswitchVal))
@ -560,6 +561,8 @@ void LoopUnswitch::SplitExitEdges(Loop *L,
BasicBlock *ExitBlock = ExitBlocks[i];
SmallVector<BasicBlock *, 4> Preds(pred_begin(ExitBlock),
pred_end(ExitBlock));
// Although SplitBlockPredecessors doesn't preserve loop-simplify in
// general, if we call it on all predecessors of all exits then it does.
SplitBlockPredecessors(ExitBlock, Preds.data(), Preds.size(),
".us-lcssa", this);
}
@ -915,10 +918,11 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
// Found a dead case value. Don't remove PHI nodes in the
// successor if they become single-entry, those PHI nodes may
// be in the Users list.
BasicBlock *Switch = SI->getParent();
BasicBlock *SISucc = SI->getSuccessor(DeadCase);
BasicBlock *Latch = L->getLoopLatch();
if (!SI->findCaseDest(SISucc)) continue; // Edge is critical.
// If the DeadCase successor dominates the loop latch, then the
// transformation isn't safe since it will delete the sole predecessor edge
// to the latch.

28
test/Transforms/LoopUnswitch/2011-06-02-CritSwitch.ll Normal file
View File

@ -0,0 +1,28 @@
; RUN: opt -loop-unswitch -disable-output
; PR10031
define i32 @test(i32 %command) {
entry:
br label %tailrecurse
tailrecurse: ; preds = %if.then14, %tailrecurse, %entry
br i1 undef, label %if.then, label %tailrecurse
if.then: ; preds = %tailrecurse
switch i32 %command, label %sw.bb [
i32 2, label %land.lhs.true
i32 0, label %land.lhs.true
]
land.lhs.true: ; preds = %if.then, %if.then
br i1 undef, label %sw.bb, label %if.then14
if.then14: ; preds = %land.lhs.true
switch i32 %command, label %tailrecurse [
i32 0, label %sw.bb
i32 1, label %sw.bb
]
sw.bb: ; preds = %if.then14
unreachable
}