use of uninitialized variables in SimpleRegisterCoalescing.cpp

[sunfishcode]

Bugzilla Link	2226
Resolution	FIXED
Resolved on	Apr 16, 2008 15:12
Version	trunk
OS	All
Attachments	this patch makes the problem more visible

Extended Description

SimpleRegisterCoalescing.cpp at line 1937 calls TargetInstrInfo::isMoveInstr
to get the source and destination registers of a move without checking
the result value to see if the instruction was actually a move. It looks like
it should be, but currently there are cases where this assumption doesn't
hold. When it doesn't the following code ends up referencing the
variables uninitialized.

For example, when compiling
test/CodeGen/Generic/2003-07-08-BadCastToBool.ll
on x86 the code at line 1073 inserts a non-move instruction into
JoinedCopies.

The attached patch demonstrates the problem by using an assert.

[llvmbot]

Valgrind spotted the following in the testcase CodeGen/PowerPC/2008-04-10-LiveIntervalCrash.ll, maybe it is the same problem:

Conditional jump or move depends on uninitialised value(s)
at 0x88FAC28: llvm::SimpleRegisterCoalescing::RemoveCopiesFromValNo(llvm::LiveInterval&, llvm::VNInfo*) (SimpleRegisterCoalescing.cpp:736)
by 0x88FDFAD: llvm::SimpleRegisterCoalescing::JoinCopy(llvm::CopyRec&, bool&) (SimpleRegisterCoalescing.cpp:1102)
by 0x88FE54F: llvm::SimpleRegisterCoalescing::CopyCoalesceInMBB(llvm::MachineBasicBlock*, std::vector<llvm::CopyRec, std::allocatorllvm::CopyRec >& (SimpleRegisterCoalescing.cpp:1669)
by 0x88FE830: llvm::SimpleRegisterCoalescing::joinIntervals() (SimpleRegisterCoalescing.cpp:1700)
by 0x88FEFB7: llvm::SimpleRegisterCoalescing::runOnMachineFunction(llvm::MachineFunction&) (SimpleRegisterCoalescing.cpp:1925)
by 0x842728B: llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (MachineFunctionPass.h:41)
by 0x8A3AAD6: llvm::FPPassManager::runOnFunction(llvm::Function&) (PassManager.cpp:1178)
by 0x8A3AD33: llvm::FunctionPassManagerImpl::run(llvm::Function&) (PassManager.cpp:1133)
by 0x8A3AE8A: llvm::FunctionPassManager::run(llvm::Function&) (PassManager.cpp:1078)
by 0x83D50CA: main (llc.cpp:296)

[llvmbot]

Fixed.
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080414/061177.html

[llvmbot]

I can confirm that this is fixed.