[llvm-commits] [PATCH] Machine code verifier pass

Jakob Stoklund Olesen stoklund at 2pi.dk
Tue May 12 13:32:34 PDT 2009

On 12/05/2009, at 21.32, Evan Cheng wrote:

> The double def is also a bug.

There are lots of physical register double defs when using sub- 
registers, I think they are introduced by the coalescer, but I am not  
sure. I have disabled the phys-double-def check for now.

Attached is take two of the machine code verifier pass. These are the  

- Change transient class ivars to method arguments as requested. This  
is much better.

- Calculate MBB reachability and exclude unreachable MBBs from some  
checks. There are sometimes dead MBBs with bad live register  

- Don't verify physical live-in lists for EH landing pads. Unwind  
creates live registers from thin air.

- Don't require PHI operands to be live-in from all predecessors. (Duh)

- Add dedicated check for PHI operands. Check needed predecessor live- 
outs individually, and require a PHI operand pair for each  
predecessor. There are many PHI instructions referring to MBBs that  
are not predecessors. That looks suspicious, but I am allowing it.

- Check for the environment variable LLVM_VERIFY_MACHINEINSTRS. When  
it is defined, enable the verifier globally, append output to a file  
instead of cerr, and don't abort on errors. This means you can say:

$ LLVM_VERIFY_MACHINEINSTRS=verify.out make check
$ find . -name verify.out -not -empty | xargs fgrep -c '*** Bad  
machine code'

I am using MachineInstr::isRegTiedToDefOperand(), and that is causing  
asserts on some PowerPC tests because  
InlineAsm::isUseOperandTiedToDef() is returning an invalid operand  

tied-badval.patch is a workaround. It is not a fix.

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