On Thu, Nov 7, 2024 at 1:41 PM Indu Bhagat <indu.bha...@oracle.com> wrote: > > subg (Subtract with Tag) is an Armv8.5-A memory tagging (MTE) > instruction. It can be used to subtract an immediate value scaled by > the tag granule from the address in the source register. > > gcc/ChangeLog: > > * config/aarch64/aarch64.md (subg): New definition. > --- > gcc/config/aarch64/aarch64.md | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md > index 8d10197c9e8d..1ec872afef71 100644 > --- a/gcc/config/aarch64/aarch64.md > +++ b/gcc/config/aarch64/aarch64.md > @@ -8193,6 +8193,23 @@ > [(set_attr "type" "memtag")] > ) > > +(define_insn "subg" > + [(set (match_operand:DI 0 "register_operand" "=rk") > + (ior:DI > + (and:DI (minus:DI (match_operand:DI 1 "register_operand" "rk") > + (match_operand:DI 2 "aarch64_granule16_uimm6" "i")) > + (const_int -1080863910568919041)) ;; 0xf0ff...
Seems like this special constant should be done defined in a define_constants. It is not obvious where this constant comes from either. Maybe with it in a define_constant with an extra comment it might be easier to understand what this constant means. Thanks, Andrew > + (ashift:DI > + (unspec:QI > + [(and:QI (lshiftrt:DI (match_dup 1) (const_int 56)) (const_int 15)) > + (match_operand:QI 3 "aarch64_memtag_tag_offset" "i")] > + UNSPEC_GEN_TAG) > + (const_int 56))))] > + "TARGET_MEMTAG" > + "subg\\t%0, %1, #%2, #%3" > + [(set_attr "type" "memtag")] > +) > + > (define_insn "subp" > [(set (match_operand:DI 0 "register_operand" "=r") > (minus:DI > -- > 2.43.0 >
