[LLVMdev] r98938 broke argument passing on MSP430?

[Chris Lattner]

On Jun 21, 2010, at 1:32 PM, Ben Ransford wrote:

> On Fri, Jun 11, 2010 at 2:55 PM, Ben Ransford <ransford at cs.umass.edu> wrote:
>> Yesterday I noticed that MSP430 argument passing is broken in trunk;
>> see http://llvm.org/PR6573 for details and testcases.  The problem is
>> that calls aren't being preceded by instructions that put the
>> arguments into registers.  I backtracked my working copy and then
>> stepped forward until it broke between r98937 and r98938.  Refining
>> further, I found that rolling back the single-statement change to
>> utils/TableGen/DAGISelMatcherGen.cpp -- something about variadic
>> instructions that was probably OK for x86, but MSP430 doesn't have
>> variadic instructions -- restored the correct behavior.  Seems like
>> r98938 either introduced a bug in DAGISelMatcherGen.cpp or exposed a
>> bug in MSP430InstrInfo.td (or similar).  That's Chris's commit; could
>> he or someone else who's comfortable with LLVM internals (I'm not)
>> help me root out the problem?
> 
> Anton graciously helped me out of band.  I'm attaching his patch
> (recomputed against ToT), which fixes a bug in MSP430InstrInfo.td.
> I'm afraid I don't know how to write a testcase for this bug.
> 
> (Key insight from Anton: attaching "SDNPVariadic" to "MSP430call"
> indicates that the *instruction selector pattern*, not the call
> instruction, is variadic.)

Applied in r106722, thanks!

-Chris