r98938 broke argument passing on MSP430?


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?

I'm asking here because I don't know if this change broke other
non-x86 architectures.


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.)


msp430-call-variadic.patch (677 Bytes)

Applied in r106722, thanks!