On Sat, Jan 6, 2024 at 2:30 PM Roger Sayle <ro...@nextmovesoftware.com> wrote:
>
>
> This patch improves the cost/gain calculation used during the i386 backend's
> SImode/DImode scalar-to-vector (STV) conversion pass. The current code
> handles loads and stores, but doesn't consider that converting other
> scalar operations with a memory destination, requires an explicit load
> before and an explicit store after the vector equivalent.
>
> To ease the review, the significant change looks like:
>
> /* For operations on memory operands, include the overhead
> of explicit load and store instructions. */
> if (MEM_P (dst))
> igain += !optimize_insn_for_size_p ()
> ? (m * (ix86_cost->int_load[2]
> + ix86_cost->int_store[2])
> - (ix86_cost->sse_load[sse_cost_idx] +
> ix86_cost->sse_store[sse_cost_idx]))
> : -COSTS_N_BYTES (8);
Please just swap true and false statements to avoid negative test.
> however the patch itself is complicated by a change in indentation
> which leads to a number of lines with only whitespace changes.
'git diff -w' to the rescue ;)
> For architectures where integer load/store costs are the same as
> vector load/store costs, there should be no change without -Os/-Oz.
>
> This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> and make -k check, both with and without --target_board=unix{-m32}
> with no new failures. Ok for mainline?
>
>
> 2024-01-06 Roger Sayle <ro...@nextmovesoftware.com>
>
> gcc/ChangeLog
> PR target/113231
> * config/i386/i386-features.cc (compute_convert_gain): Include
> the overhead of explicit load and store (movd) instructions when
> converting non-store scalar operations with memory destinations.
>
> gcc/testsuite/ChangeLog
> PR target/113231
> * gcc.target/i386/pr113231.c: New test case.
OK with the above proposed change.
Thanks,
Uros.
