Thorsten Schütt 45162635bf
[GlobalISel] Combine [s,z]ext of undef into 0 (#117439)
Alternative for https://github.com/llvm/llvm-project/pull/113764

It builds on a minimalistic approach with the legality check in match
and a blind apply. The precise patterns are used for better compile-time
and modularity. It also moves the pattern check into combiner. While
unary_undef_to_zero and propagate_undef_any_op rely on custom C++ code
for pattern matching.

Is there a limit on the number of patterns?

G_ANYEXT of undef -> undef
G_SEXT of undef -> 0
G_ZEXT of undef -> 0

The combine is not a member of the post legalizer combiner for AArch64.

Test:
llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir
2024-12-03 07:14:49 +01:00
..

++ SVE CodeGen Warnings ++

When the WARN check lines fail in the SVE codegen tests it most likely means you
have introduced a warning due to:
1. Adding an invalid call to VectorType::getNumElements() or EVT::getVectorNumElements()
   when the type is a scalable vector.
2. Relying upon an implicit cast conversion from TypeSize to uint64_t.

For generic code, please modify your code to work with ElementCount and TypeSize directly.
For target-specific code that only deals with fixed-width vectors, use the fixed-size interfaces.
Please refer to the code where those functions live for more details.