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fix two problems with machine sinking:

Browse Source 
1. Sinking would crash when the first instruction of a block was
   sunk due to iterator problems.
2. Instructions could be sunk to their current block, causing an
   infinite loop.

This fixes PR3968

llvm-svn: 68787
This commit is contained in:
Chris Lattner 2009-04-10 16:38:36 +00:00
parent b85fd685f8
commit 0577b8e2ef
2 changed files with 42 additions and 12 deletions
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38
lib/CodeGen/MachineSink.cpp
View File

@ -111,20 +111,29 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
}
bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
bool MadeChange = false;
// Can't sink anything out of a block that has less than two successors.
if (MBB.succ_size() <= 1) return false;
if (MBB.succ_size() <= 1 || MBB.empty()) return false;
bool MadeChange = false;
// Walk the basic block bottom-up. Remember if we saw a store.
bool SawStore = false;
for (MachineBasicBlock::iterator I = MBB.end(); I != MBB.begin(); ){
MachineBasicBlock::iterator LastIt = I;
if (SinkInstruction(--I, SawStore)) {
I = LastIt;
++NumSunk;
}
}
MachineBasicBlock::iterator I = MBB.end();
--I;
bool ProcessedBegin, SawStore = false;
do {
MachineInstr *MI = I; // The instruction to sink.
// Predecrement I (if it's not begin) so that it isn't invalidated by
// sinking.
ProcessedBegin = I == MBB.begin();
if (!ProcessedBegin)
--I;
if (SinkInstruction(MI, SawStore))
++NumSunk, MadeChange = true;
// If we just processed the first instruction in the block, we're done.
} while (!ProcessedBegin);
return MadeChange;
}
@ -218,6 +227,11 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
if (SuccToSinkTo->isLandingPad())
return false;
// If is not possible to sink an instruction into its own block. This can
// happen with loops.
if (MI->getParent() == SuccToSinkTo)
return false;
DEBUG(cerr << "Sink instr " << *MI);
DEBUG(cerr << "to block " << *SuccToSinkTo);

16
test/CodeGen/Generic/2009-04-10-SinkCrash.ll Normal file
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@ -0,0 +1,16 @@
; RUN: llvm-as < %s | llc
define void @QRiterate(i32 %p.1, double %tmp.212) nounwind {
entry:
br i1 false, label %shortcirc_next.1, label %exit.1.critedge
shortcirc_next.1: ; preds = %shortcirc_next.1, %entry
%tmp.213 = fcmp une double %tmp.212, 0.000000e+00 ; <i1> [#uses=1]
br i1 %tmp.213, label %shortcirc_next.1, label %exit.1
exit.1.critedge: ; preds = %entry
ret void
exit.1: ; preds = %shortcirc_next.1
ret void
}