[clang][ARM] Refactor argument handling in `EmitAArch64BuiltinExpr` (1/2) (NFC) (#181794)
Refactor `EmitAArch64BuiltinExpr` so that all AArch64/NEON builtins
handled by this hook _and marked as non-overloaded_ share a common path
for generating LLVM IR arguments (collected into the `Ops`
`SmallVector<Value*>`) (*)
Previously, the argument emission loop unconditionally skipped the
trailing argument:
```cpp
for (unsigned i = 0, e = E->getNumArgs() - 1; i != e; ++i)
```
This was originally intended to ignore the extra Sema-only argument
used by overloaded NEON builtins (e.g. the type discriminator passed
by `__builtin_neon_*` intrinsics). However, this logic was applied
unconditionally.
This patch updates the loop to skip the trailing argument only when
`HasExtraNeonArgument` returns true for non-SISD builtins:
```cpp
bool HasExtraArg = !IsSISD && HasExtraNeonArgument(BuiltinID);
unsigned NumArgs =
E->getNumArgs() - (HasExtraArg ? 1 : 0);
for (unsigned i = 0, e = NumArgs; i != e; ++i)
```
This preserves existing IR generation behaviour while making the
handling of Sema-only NEON discriminator arguments explicit.
For context, type discriminators can be found in definitions of various
builtins in `arm_neon.h`. For example, `vsriq_n_p64(<args>)` expands
into the following call:
```cpp
__builtin_neon_vsriq_n_v(<args>, 38)
```
The trailing `38` encodes the concrete NEON vector type
(e.g. `poly64x2_t`) for overload resolution in Sema; it is not
semantically part of the operation and is ignored during IR generation.
As part of this change, `HasExtraNeonArgument` was completed so
that these discriminator arguments are correctly identified.
No functional change intended.
(*) This refers to two large `switch` stmts inside
`EmitAArch64BuiltinExpr` that are meant to switch the processing into
non-overloaded and overloaded builtins. The intended split between
non-overloaded and overloaded builtins is not consistently enforced: the
second switch (nominally handling overloaded builtins) also processes
some non-overloaded cases. This patch refactors only the first switch
and prepares for a follow-up cleanup in 2/2.
llvm-project
2d69ab26 - [clang][ARM] Refactor argument handling in `EmitAArch64BuiltinExpr` (1/2) (NFC) (#181794)
