Hi Claudiu,
> The patch looks sane. Have you run dejagnu test suite?
I've not yet managed to set up an emulator or compile the entire toolchain,
so my dejagnu results are only useful for catching (serious) problems in the
compile only tests:
=== gcc Summary ===
# of expected passes 91875
# of unexpected failures 23768
# of unexpected successes 23
# of expected failures 1038
# of unresolved testcases 19490
# of unsupported tests 3819
/home/roger/GCC/arc-linux/gcc/xgcc version 14.0.0 20230828 (experimental)
(GCC)
If someone could double check there are no issues on real hardware that
would be great. I'm not sure if ARC is one of the targets covered by Jeff
Law's
compile farm?
> -----Original Message-----
> From: Roger Sayle <ro...@nextmovesoftware.com>
> Sent: Friday, September 29, 2023 6:54 PM
> To: gcc-patches@gcc.gnu.org
> Cc: Claudiu Zissulescu <claz...@synopsys.com>
> Subject: [ARC PATCH] Use rlc r0,0 to implement scc_ltu (i.e. carry_flag ?
1 : 0)
>
>
> This patch teaches the ARC backend that the contents of the carry flag can
be
> placed in an integer register conveniently using the "rlc rX,0"
> instruction, which is a rotate-left-through-carry using zero as a source.
> This is a convenient special case for the LTU form of the scc pattern.
>
> unsigned int foo(unsigned int x, unsigned int y) {
> return (x+y) < x;
> }
>
> With -O2 -mcpu=em this is currently compiled to:
>
> foo: add.f 0,r0,r1
> mov_s r0,1 ;3
> j_s.d [blink]
> mov.hs r0,0
>
> [which after an addition to set the carry flag, sets r0 to 1, followed by
a
> conditional assignment of r0 to zero if the carry flag is clear]. With
the new
> define_insn/optimization in this patch, this becomes:
>
> foo: add.f 0,r0,r1
> j_s.d [blink]
> rlc r0,0
>
> This define_insn is also a useful building block for implementing shifts
and rotates.
>
> Tested on a cross-compiler to arc-linux (hosted on x86_64-pc-linux-gnu),
and a
> partial tool chain, where the new case passes and there are no new
regressions.
> Ok for mainline?
>
>
> 2023-09-29 Roger Sayle <ro...@nextmovesoftware.com>
>
> gcc/ChangeLog
> * config/arc/arc.md (CC_ltu): New mode iterator for CC and CC_C.
> (scc_ltu_<mode>): New define_insn to handle LTU form of scc_insn.
> (*scc_insn): Don't split to a conditional move sequence for LTU.
>
> gcc/testsuite/ChangeLog
> * gcc.target/arc/scc-ltu.c: New test case.
>
>
> Thanks in advance,
> Roger
> --
