This patch addresses a missed optimization opportunity in the RTL
optimization passes.  The function simplify_const_binary_operation
will constant fold binary operators with two CONST_INT operands,
and those with two CONST_VECTOR operands, but is missing compile-time
evaluation of binary operators with a CONST_VECTOR and a CONST_INT,
such as vector shifts and rotates.

My first version of this patch didn't contain a switch statement to
explicitly check for valid binary opcodes, which bootstrapped and
regression tested fine, but by paranoia has got the better of me,
so this version now checks that VEC_SELECT or some funky (future)
rtx_code doesn't cause problems.

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 (in stage 1)?


2024-01-26  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
        * simplify-rtx.cc (simplify_const_binary_operation): Constant
        fold binary operations where the LHS is CONST_VECTOR and the
        RHS is CONST_INT (or CONST_DOUBLE) such as vector shifts.


Thanks in advance,
Roger
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