df1f0eef67
On targets that use reload, call_fixed_reg_set is structurally:
fixed_reg_set -- reginfo.c
| (call_used_reg_set & ~have_save_mode) -- first loop in init_caller_save
| ~have_save_insn -- final loop in init_caller_save
(where "have_save_mode" and "have_save_insn" are just my names).
But the final loop in init_caller_save does:
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
for (j = 1; j <= MOVE_MAX_WORDS; j++)
if (reg_save_code (i,regno_save_mode[i][j]) == -1)
This last condition ought to be true whenever:
regno_save_mode[i][j] == VOIDmode
since either targetm.hard_regno_mode_ok (i, VOIDmode) should be
false or the VOIDmode save & restore shouldn't match any move insn.
And after the first loop, regno_save_mode[i][j] == VOIDmode whenever
!call_used_regs[i]. So the above is actually:
fixed_reg_set
| (call_used_reg_set & ~have_save_mode)
| (~call_used_reg_set | ~have_save_insn)
which simplifies to:
fixed_reg_set -- reginfo.c
| ~have_save_mode -- first loop in init_caller_save
| ~have_save_insn -- final loop in init_caller_save
| ~call_used_reg_set -- final loop in init_caller_save
So:
~call_fixed_reg_set == (~fixed_reg_set
& have_save_mode
& have_save_insn
& call_used_reg_set) [A]
All users have the form:
(call_used_reg_set or some subset) & ~(call_fixed_reg_set | ...)
i.e.:
(call_used_reg_set or some subset) & ~call_fixed_reg_set & ~(...)
We can therefore drop the "& call_used_reg_set" from [A], leaving:
~fixed_reg_set & have_save_mode & have_save_insn
This patch combines have_save_mode & have_save_insn into a single
condition "a save is possible", represented as savable_regs.
We can then substitute:
~call_fixed_reg_set --> ~fixed_reg_set & savable_regs
(registers we can actually save around calls)
The patch also sets regno_save_mode[i][j] for all registers,
in case non-default ABIs require a save when the default ABI
doesn't. This ensures that savable_regs (like fixed_reg_set but
unlike call_fixed_reg_set) isn't affected by the ABI. This only
becomes significant with later patches and at this point is just
a simplification.
Since init_caller_save is only called for reload targets,
the default assumption for LRA is that all registers are savable,
just like the default assumption before the patch was that
(~)call_fixed_reg_set == (~)fixed_reg_set.
2019-09-10 Richard Sandiford <richard.sandiford@arm.com>
gcc/
* hard-reg-set.h (target_hard_regs::x_call_fixed_reg_set): Delete.
(target_hard_regs::x_savable_regs): New field.
(call_fixed_reg_set): Delete.
(savable_regs): New macro,
* reginfo.c (globalize_reg): Don't set call_fixed_reg_set.
(init_reg_sets_1): Likewise. Initialize savable_regs.
* caller-save.c (init_caller_save): Invoke HARD_REGNO_CALLER_SAVE_MODE
for all registers. Set savable_regs instead of call_fixed_reg_set.
(setup_save_areas, save_call_clobbered_regs): Replace uses of
~call_fixed_reg_set with ~fixed_reg_set & savable_regs.
* config/sh/sh.c (output_stack_adjust): Likewise.
From-SVN: r275598
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