Repost with requested changes. I've extracted the logic that omits
frame saves from rs6000_frame_related to a new function, because it's
easier to document that way. The logic has been simplified a little
too: fixed_reg_p doesn't need to be called there.
PR target/80938
* config/rs6000/rs6000.c (rs6000_savres_strategy): Revert 2017-08-09.
Don't use store multiple if only one reg needs saving.
(interesting_frame_related_regno): New function.
(rs6000_frame_related): Don't emit eh_frame for regs that
don't need saving.
(rs6000_emit_epilogue): Likewise.
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f9aa13b..178632e 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -24445,20 +24445,36 @@ rs6000_savres_strategy (rs6000_stack_t *info,
&& flag_shrink_wrap_separate
&& optimize_function_for_speed_p (cfun)))
{
- /* Prefer store multiple for saves over out-of-line routines,
- since the store-multiple instruction will always be smaller. */
- strategy |= SAVE_INLINE_GPRS | SAVE_MULTIPLE;
-
- /* The situation is more complicated with load multiple. We'd
- prefer to use the out-of-line routines for restores, since the
- "exit" out-of-line routines can handle the restore of LR and the
- frame teardown. However if doesn't make sense to use the
- out-of-line routine if that is the only reason we'd need to save
- LR, and we can't use the "exit" out-of-line gpr restore if we
- have saved some fprs; In those cases it is advantageous to use
- load multiple when available. */
- if (info->first_fp_reg_save != 64 || !lr_save_p)
- strategy |= REST_INLINE_GPRS | REST_MULTIPLE;
+ int count = 0;
+ for (int i = info->first_gp_reg_save; i < 32; i++)
+ if (save_reg_p (i))
+ count++;
+
+ if (count <= 1)
+ /* Don't use store multiple if only one reg needs to be
+ saved. This can occur for example when the ABI_V4 pic reg
+ (r30) needs to be saved to make calls, but r31 is not
+ used. */
+ strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
+ else
+ {
+ /* Prefer store multiple for saves over out-of-line
+ routines, since the store-multiple instruction will
+ always be smaller. */
+ strategy |= SAVE_INLINE_GPRS | SAVE_MULTIPLE;
+
+ /* The situation is more complicated with load multiple.
+ We'd prefer to use the out-of-line routines for restores,
+ since the "exit" out-of-line routines can handle the
+ restore of LR and the frame teardown. However if doesn't
+ make sense to use the out-of-line routine if that is the
+ only reason we'd need to save LR, and we can't use the
+ "exit" out-of-line gpr restore if we have saved some
+ fprs; In those cases it is advantageous to use load
+ multiple when available. */
+ if (info->first_fp_reg_save != 64 || !lr_save_p)
+ strategy |= REST_INLINE_GPRS | REST_MULTIPLE;
+ }
}
/* Using the "exit" out-of-line routine does not improve code size
@@ -24467,21 +24483,6 @@ rs6000_savres_strategy (rs6000_stack_t *info,
else if (!lr_save_p && info->first_gp_reg_save > 29)
strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
- /* We can only use save multiple if we need to save all the registers from
- first_gp_reg_save. Otherwise, the CFI gets messed up (we save some
- register we do not restore). */
- if (strategy & SAVE_MULTIPLE)
- {
- int i;
-
- for (i = info->first_gp_reg_save; i < 32; i++)
- if (fixed_reg_p (i) || !save_reg_p (i))
- {
- strategy &= ~SAVE_MULTIPLE;
- break;
- }
- }
-
/* Don't ever restore fixed regs. */
if ((strategy & (REST_INLINE_GPRS | REST_MULTIPLE)) != REST_INLINE_GPRS)
for (int i = info->first_gp_reg_save; i < 32; i++)
@@ -25654,6 +25655,32 @@ output_probe_stack_range (rtx reg1, rtx reg2)
return "";
}
+/* This function is called when rs6000_frame_related is processing
+ SETs within a PARALLEL, and returns whether the REGNO save ought to
+ be marked RTX_FRAME_RELATED_P. The PARALLELs involved are those
+ for out-of-line register save functions, store multiple, and the
+ Darwin world_save. They may contain registers that don't really
+ need saving. */
+
+static bool
+interesting_frame_related_regno (unsigned int regno)
+{
+ /* Saves apparently of r0 are actually saving LR. */
+ if (regno == 0)
+ return true;
+ /* If we see CR2 then we are here on a Darwin world save. Saves of
+ CR2 signify the whole CR is being saved. */
+ if (regno == CR2_REGNO)
+ return true;
+ /* Omit frame info for any user-defined global regs. If frame info
+ is supplied for them, frame unwinding will restore a user reg.
+ Also omit frame info for any reg we don't need to save, as that
+ bloats eh_frame and can cause problems with shrink wrapping.
+ Since global regs won't be seen as needing to be saved, both of
+ these conditions are covered by save_reg_p. */
+ return save_reg_p (regno);
+}
+
/* Add to 'insn' a note which is PATTERN (INSN) but with REG replaced
with (plus:P (reg 1) VAL), and with REG2 replaced with REPL2 if REG2
is not NULL. It would be nice if dwarf2out_frame_debug_expr could
@@ -25688,13 +25715,8 @@ rs6000_frame_related (rtx_insn *insn, rtx reg,
HOST_WIDE_INT val,
{
rtx set = XVECEXP (pat, 0, i);
- /* If this PARALLEL has been emitted for out-of-line
- register save functions, or store multiple, then omit
- eh_frame info for any user-defined global regs. If
- eh_frame info is supplied, frame unwinding will
- restore a user reg. */
if (!REG_P (SET_SRC (set))
- || !fixed_reg_p (REGNO (SET_SRC (set))))
+ || interesting_frame_related_regno (REGNO (SET_SRC (set))))
RTX_FRAME_RELATED_P (set) = 1;
}
RTX_FRAME_RELATED_P (insn) = 1;
@@ -25731,9 +25753,8 @@ rs6000_frame_related (rtx_insn *insn, rtx reg,
HOST_WIDE_INT val,
set = simplify_replace_rtx (set, reg2, repl2);
XVECEXP (pat, 0, i) = set;
- /* Omit eh_frame info for any user-defined global regs. */
if (!REG_P (SET_SRC (set))
- || !fixed_reg_p (REGNO (SET_SRC (set))))
+ || interesting_frame_related_regno (REGNO (SET_SRC (set))))
RTX_FRAME_RELATED_P (set) = 1;
}
}
@@ -27956,7 +27977,8 @@ rs6000_emit_epilogue (int sibcall)
RTVEC_ELT (p, j++)
= gen_frame_load (reg,
frame_reg_rtx, info->gp_save_offset + reg_size *
i);
- if (flag_shrink_wrap)
+ if (flag_shrink_wrap
+ && save_reg_p (info->first_gp_reg_save + i))
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
}
for (i = 0; info->first_altivec_reg_save + i <= LAST_ALTIVEC_REGNO; i++)
@@ -27965,7 +27987,8 @@ rs6000_emit_epilogue (int sibcall)
RTVEC_ELT (p, j++)
= gen_frame_load (reg,
frame_reg_rtx, info->altivec_save_offset + 16 *
i);
- if (flag_shrink_wrap)
+ if (flag_shrink_wrap
+ && save_reg_p (info->first_altivec_reg_save + i))
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
}
for (i = 0; info->first_fp_reg_save + i <= 63; i++)
@@ -27975,7 +27998,8 @@ rs6000_emit_epilogue (int sibcall)
info->first_fp_reg_save + i);
RTVEC_ELT (p, j++)
= gen_frame_load (reg, frame_reg_rtx, info->fp_save_offset + 8 * i);
- if (flag_shrink_wrap)
+ if (flag_shrink_wrap
+ && save_reg_p (info->first_fp_reg_save + i))
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
}
RTVEC_ELT (p, j++)
@@ -28096,7 +28120,8 @@ rs6000_emit_epilogue (int sibcall)
&& (flag_shrink_wrap
|| (offset_below_red_zone_p
(info->altivec_save_offset
- + 16 * (i - info->first_altivec_reg_save)))))
+ + 16 * (i - info->first_altivec_reg_save))))
+ && save_reg_p (i))
{
rtx reg = gen_rtx_REG (V4SImode, i);
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
@@ -28308,7 +28333,8 @@ rs6000_emit_epilogue (int sibcall)
for (i = info->first_altivec_reg_save; i <= LAST_ALTIVEC_REGNO; ++i)
if (((strategy & REST_INLINE_VRS) == 0
|| (info->vrsave_mask & ALTIVEC_REG_BIT (i)) != 0)
- && (DEFAULT_ABI == ABI_V4 || flag_shrink_wrap))
+ && (DEFAULT_ABI == ABI_V4 || flag_shrink_wrap)
+ && save_reg_p (i))
{
rtx reg = gen_rtx_REG (V4SImode, i);
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
@@ -28654,7 +28680,8 @@ rs6000_emit_epilogue (int sibcall)
RTVEC_ELT (p, elt++)
= gen_frame_load (reg, sp_reg_rtx, info->fp_save_offset + 8 * i);
- if (flag_shrink_wrap)
+ if (flag_shrink_wrap
+ && save_reg_p (info->first_fp_reg_save + i))
cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
}
--
Alan Modra
Australia Development Lab, IBM
