[Bug rtl-optimization/63620] RELOAD lost SET_GOT dependency on Darwin

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63620

UroÅ Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra
             Target|Darwin                      |x86
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-10-26
   Target Milestone|---                         |5.0
     Ever confirmed|0                           |1

--- Comment #3 from UroÅ Bizjak <ubizjak at gmail dot com> ---
Confirmed. This will affect all SSE targets.

This is an RA issue. When RA kicks the constant to a memory, PIC register
should be marked as live for the insn that accesses memory.

We start with:

(insn 21 17 22 3 (set (mem:TF (pre_dec:SI (reg/f:SI 7 sp)) [1  S16 A128])
        (const_double:TF 1.0e+29 [0x0.a18f07d736b90be55p+97])) pr63620.c:21 121
{*pushtf}
     (expr_list:REG_ARGS_SIZE (const_int 16 [0x10])
        (nil)))

and RA does:

     Choosing alt 0 in insn 21:  (0) =<  (1) x {*pushtf}
      Creating newreg=93, assigning class GENERAL_REGS to addr r93
       Change to class INDEX_REGS for r93
      Creating newreg=94, assigning class SSE_REGS to r94
   21: [--sp:SI]=r94:TF
      REG_ARGS_SIZE 0x10
    Inserting insn reload before:
   46: r93:SI=r87:SI+const(unspec[`*LC0'] 10)
      REG_EQUAL `*LC0'
   47: r94:TF=[r93:SI]

which results in:

(insn 46 17 47 3 (set (reg:SI 0 ax [93])
        (plus:SI (reg:SI 0 ax [87])
            (const:SI (unspec:SI [
                        (symbol_ref/u:SI ("*LC0") [flags 0x2])
                    ] UNSPEC_MACHOPIC_OFFSET)))) pr63620.c:21 213 {*leasi}
     (expr_list:REG_EQUAL (symbol_ref/u:SI ("*LC0") [flags 0x2])
        (nil)))
(insn 47 46 21 3 (set (reg:TF 23 xmm2 [94])
        (mem/u/c:TF (reg:SI 0 ax [93]) [1  S16 A128])) pr63620.c:21 126
{*movtf_internal}
     (nil))
(insn 21 47 22 3 (set (mem:TF (pre_dec:SI (reg/f:SI 7 sp)) [1  S16 A128])
        (reg:TF 23 xmm2 [94])) pr63620.c:21 121 {*pushtf}
     (expr_list:REG_ARGS_SIZE (const_int 16 [0x10])
        (nil)))

When the constant is pushed to a memory to satisfy operand constraints, the PIC
register should be marked as live (== used by the insn that reads memory). RA
even sets the REG_EQUAL to a symbol_ref in the reloading insn.

The patch at Comment #2 will just paper over the issue.