[PATCH] More use MEM_EXPR only if MEM_P is true

[H.J. Lu]

On Wed, Jun 4, 2025 at 4:13 PM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> Richard Biener <richard.guent...@gmail.com> writes:
> > On Wed, Jun 4, 2025 at 7:28 AM H.J. Lu <hjl.to...@gmail.com> wrote:
> >>
> >> On s390x, for input:
> >>
> >> (call_insn/u 7 6 11 2 (parallel [
> >>             (set (reg:SI 2 %r2)
> >>                 (call (subreg:QI (symbol_ref:SI ("__tls_get_offset")
> >> [flags 0x1]) 3)
> >>                     (const_int 0 [0])))
> >>             (clobber (reg:SI 14 %r14))
> >>             (use (unspec:SI [
> >>                         (const_int 0 [0])
> >>                     ] UNSPEC_TLSLDM))
> >>         ]) "/tmp/foo.c":12:26 2602 {*brasl_tls}
> >>      (expr_list:REG_EH_REGION (const_int -2147483648 [0xffffffff80000000])
> >>         (nil))
> >>     (expr_list (use (reg:SI 2 %r2))
> >>         (expr_list (use (reg:SI 12 %r12))
> >>             (nil))))
> >>
> >> after r16-1041-g2da641d0170090, get_call_rtx_from returns:
> >>
> >> (call (subreg:QI (symbol_ref:SI ("__tls_get_offset") [flags 0x1]) 3)
> >>     (const_int 0 [0]))
> >
> > That's a strange call!
>
> Yeah.  Are we sure it's really correct?  Taken literally, it says that
> we're interpreting the symbol __tls_get_offset as a sequence of instructions.
>
> Also, the docs say:
>
>   @item (call @var{function} @var{nargs})
>   Represents a function call.  @var{function} is a @code{mem} expression
>   whose address is the address of the function to be called.
>
> So I don't object to the patch, but it seems like it might be papering
> over a target bug.  cc:ing s390 maintainers.
>
> Richard

After r16-1041-g2da641d0170090, get_call_rtx_from returns

(call (unspec:SI [
            (mem:SI (reg/f:SI 98) [0 MEM[(void (*<T2f6>) (struct test_st))209715
2B] S4 A32])
        ] UNSPEC_NONSECURE_MEM)
    (const_int 0 [0]))

on

(call_insn 14 13 0 (parallel [
            (call (unspec:SI [
                        (mem:SI (reg/f:SI 98) [0 MEM[(void (*<T2f6>) (struct tes
t_st))2097152B] S4 A32])
                    ] UNSPEC_NONSECURE_MEM)
                (const_int 0 [0]))
            (use (const_int 0 [0]))
            (clobber (reg:SI 14 lr))
        ]) "/export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/arm/cmse
/mainline/8_1m/../../bitfield-4.x":38:3 -1
     (nil)
    (nil))

Update to check MEM_P before using MEM_EXPR in emit_call_1 and
rest_of_insert_endbr_and_patchable_area.

PR other/120493
* calls.cc (emit_call_1): Use MEM_EXPR only if MEM_P is true.
* config/i386/i386-features.cc
(rest_of_insert_endbr_and_patchable_area): Likewise.


-- 
H.J.