RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2025-01-22 18:35:45 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Fix mishandling of the infinite loop case when merging two blocks. This

Browse Source 
fixes PR2540.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53533 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-07-13 22:23:11 +00:00
parent b824512b8d
commit 093a438502
2 changed files with 62 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -68,11 +68,10 @@ static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
succ_end(ExistPred) && "ExistPred is not a predecessor of Succ!");
if (!isa<PHINode>(Succ->begin())) return; // Quick exit if nothing to do
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
Value *V = PN->getIncomingValueForBlock(ExistPred);
PN->addIncoming(V, NewPred);
}
PHINode *PN;
for (BasicBlock::iterator I = Succ->begin();
(PN = dyn_cast<PHINode>(I)); ++I)
PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
@ -860,7 +859,7 @@ static bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i)
if (NewSI->getSuccessor(i) == BB) {
if (InfLoopBlock == 0) {
// Insert it at the end of the loop, because it's either code,
// Insert it at the end of the function, because it's either code,
// or it won't matter if it's hot. :)
InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
@ -1430,11 +1429,11 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
/// setcc into the predecessor and use logical operations to pick the right
/// destination.
static bool FoldBranchToCommonDest(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
BasicBlock *BB = BI->getParent();
// Only allow this if the condition is a simple instruction that can be
// executed unconditionally. It must be in the same block as the branch, and
// must be at the front of the block.
@ -1456,6 +1455,9 @@ static bool FoldBranchToCommonDest(BranchInst *BI) {
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *PredBlock = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
// Check that we have two conditional branches. If there is a PHI node in
// the common successor, verify that the same value flows in from both
// blocks.
if (PBI == 0 || PBI->isUnconditional() ||
!SafeToMergeTerminators(BI, PBI))
continue;
@ -1596,18 +1598,25 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
// Finally, if everything is ok, fold the branches to logical ops.
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
// If OtherDest *is* BB, then this is a basic block with just
// a conditional branch in it, where one edge (OtherDesg) goes
// back to the block. We know that the program doesn't get
// stuck in the infinite loop, so the condition must be such
// that OtherDest isn't branched through. Forward to CommonDest,
// and avoid an infinite loop at optimizer time.
if (OtherDest == BB)
OtherDest = CommonDest;
DOUT << "FOLDING BRs:" << *PBI->getParent()
<< "AND: " << *BI->getParent();
// If OtherDest *is* BB, then BB is a basic block with a single conditional
// branch in it, where one edge (OtherDest) goes back to itself but the other
// exits. We don't *know* that the program avoids the infinite loop
// (even though that seems likely). If we do this xform naively, we'll end up
// recursively unpeeling the loop. Since we know that (after the xform is
// done) that the block *is* infinite if reached, we just make it an obviously
// infinite loop with no cond branch.
if (OtherDest == BB) {
// Insert it at the end of the function, because it's either code,
// or it won't matter if it's hot. :)
BasicBlock *InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
OtherDest = InfLoopBlock;
}
DOUT << *PBI->getParent()->getParent();
// BI may have other predecessors. Because of this, we leave

36
test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll Normal file
View File

@ -0,0 +1,36 @@
; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep {%outval = phi i32 .*mux}
; PR2540
; Outval should end up with a select from 0/2, not all constants.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
target triple = "i386-pc-linux-gnu"
@g_37 = common global i32 0 ; <i32*> [#uses=1]
@.str = internal constant [4 x i8] c"%d\0A\00" ; <[4 x i8]*> [#uses=1]
define i32 @main() nounwind {
entry:
%l = load i32* @g_37, align 4 ; <i32> [#uses=1]
%cmpa = icmp ne i32 %l, 0 ; <i1> [#uses=3]
br i1 %cmpa, label %func_1.exit, label %mooseblock
mooseblock: ; preds = %entry
%cmpb = icmp eq i1 %cmpa, false ; <i1> [#uses=2]
br i1 %cmpb, label %monkeyblock, label %beeblock
monkeyblock: ; preds = %monkeyblock, %mooseblock
br i1 %cmpb, label %cowblock, label %monkeyblock
beeblock: ; preds = %beeblock, %mooseblock
br i1 %cmpa, label %cowblock, label %beeblock
cowblock: ; preds = %beeblock, %monkeyblock
%cowval = phi i32 [ 2, %beeblock ], [ 0, %monkeyblock ] ; <i32> [#uses=1]
br label %func_1.exit
func_1.exit: ; preds = %cowblock, %entry
%outval = phi i32 [ %cowval, %cowblock ], [ 1, %entry ] ; <i32> [#uses=1]
%pout = tail call i32 (i8*, ...)* @printf( i8* noalias getelementptr ([4 x i8]* @.str, i32 0, i32 0), i32 %outval ) nounwind ; <i32> [#uses=0]
ret i32 0
}
declare i32 @printf(i8*, ...) nounwind