gnu /
gcc /
028059b46ec9aef7dd447792c579f35396751068 aarch64: Tweak MLA vector costs
The issue-based vector costs currently assume that a multiply-add
sequence can be implemented using a single instruction. This is
generally true for scalars (which have a 4-operand instruction)
and SVE (which allows the output to be tied to any input).
However, for Advanced SIMD, multiplying two values and adding
an invariant will end up being a move and an MLA.
The only target to use the issue-based vector costs is Neoverse V1,
which would generally prefer SVE in this case anyway. I therefore
don't have a self-contained testcase. However, the distinction
becomes more important with a later patch.
gcc/
* config/aarch64/aarch64.c (aarch64_multiply_add_p): Add a vec_flags
parameter. Detect cases in which an Advanced SIMD MLA would almost
certainly require a MOV.
(aarch64_count_ops): Update accordingly.
1 file changed
