| Issue |
87459
|
| Summary |
[GISel] Add variable operand MIR patterns
|
| Labels |
llvm:globalisel
|
| Assignees |
Pierre-vh
|
| Reporter |
Pierre-vh
|
## Description
Allow "parameter packs" or similar for MIR patterns to support matching any number of operands.
e.g. `G_BUILD_VECTOR` has a variable number of operands, and currently we can only write patterns for a fixed number of operands.
## Optional goals:
- Accessing the front or back of the variadic operands list
- Accessing the nth item of the variadic operands list
- Additional constraints such as min/max number of arguments.
- Rewriting the variadic operands
- This isn't as important I think, I can't think of many patterns that'd need a variadic instruction in and out. Do it if it's trivial?
## Syntax suggestion
- `G_BUILD_VECTOR $x, $y, varargs:$others`
- `G_BUILD_VECTOR $x, $y, varargs<2,4>:$others // 2 to 4 operands`
## Potential issues
- Should the variadic operand(s) act as "one or more" or "zero or more"? e.g. in the first example above, should a 2-operand BUILD_VECTOR be allowed, or does `varargs:$others` implies at least 3 operands in total?
## Related
#87194
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