There were two issues here:
1. Tail calls where the tail-callee receives modified parameters are
hazardous and only work if the parameter is return or discardable.
Otherwise, the caller of the function that executes the tail-call may
not expect some of the parameters to be clobbered.
2. There was also an indexing confusion with the call instruction vs.
call signature parameters. The call instruction has not been adapted
to the new lowered signatures, where the system args are prepended. To
make things clearer, split the loop into two, one iterating over
parameters in the call signature and one for parameters of the call
instruction.
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39579>
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