https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64479
--- Comment #2 from Oleg Endo <olegendo at gcc dot gnu.org> ---
The *cbranch_t splitter is done like 4 times, because there are 4 split passes.
The last split pass is split5, which is done right after the delayed-branch
pass. Before delayed-branch handling the call insn looks like:
(call_insn 13 79 14 2 (parallel [
(call (mem:SI (reg/f:SI 1 r1 [167]) [0 bar S4 A32])
(const_int 0 [0]))
(use (reg:PSI 151 ))
(clobber (reg:SI 146 pr))
]) sh_tmp.cpp:453 304 {calli}
(expr_list:REG_DEAD (reg:PSI 151 )
(expr_list:REG_DEAD (reg:SI 4 r4)
(expr_list:REG_DEAD (reg/f:SI 1 r1 [167])
(nil))))
(expr_list:REG_UNUSED (use (reg:SI 4 r4))
(nil)))
And modified_between_p returns true.
After delayed-branch pass the call insn looks like:
(insn 122 60 14 (sequence [
(call_insn 13 60 12 (parallel [
(call (mem:SI (reg/f:SI 1 r1 [167]) [0 bar S4 A32])
(const_int 0 [0]))
(use (reg:PSI 151 ))
(clobber (reg:SI 146 pr))
]) sh_tmp.cpp:453 304 {calli}
(expr_list:REG_DEAD (reg:PSI 151 )
(expr_list:REG_DEAD (reg:SI 4 r4)
(expr_list:REG_DEAD (reg/f:SI 1 r1 [167])
(nil))))
(expr_list:REG_UNUSED (use (reg:SI 4 r4))
(nil)))
(insn 12 13 14 (set (reg:SI 4 r4)
(reg/f:SI 15 r15)) 247 {movsi_ie}
(nil))
]) sh_tmp.cpp:453 -1
(nil))
And modified_between_p returns false, because the function reg_set_p doesn't
handle sequence rtx codes.
This could be a fix:
Index: gcc/rtlanal.c
===================================================================
--- gcc/rtlanal.c (revision 218544)
+++ gcc/rtlanal.c (working copy)
@@ -875,17 +875,24 @@
{
/* We can be passed an insn or part of one. If we are passed an insn,
check if a side-effect of the insn clobbers REG. */
- if (INSN_P (insn)
- && (FIND_REG_INC_NOTE (insn, reg)
- || (CALL_P (insn)
- && ((REG_P (reg)
- && REGNO (reg) < FIRST_PSEUDO_REGISTER
- && overlaps_hard_reg_set_p (regs_invalidated_by_call,
- GET_MODE (reg), REGNO (reg)))
- || MEM_P (reg)
- || find_reg_fusage (insn, CLOBBER, reg)))))
- return 1;
+ if (INSN_P (insn) && FIND_REG_INC_NOTE (insn, reg))
+ return true;
+ /* After delay slot handling, call and branch insns might be in a
+ sequence. Check all the elements there. */
+ if (INSN_P (insn) && GET_CODE (PATTERN (insn)) == SEQUENCE)
+ for (int i = 0; i < XVECLEN (PATTERN (insn), 0); ++i)
+ if (reg_set_p (reg, XVECEXP (PATTERN (insn), 0, i)))
+ return true;
+
+ if (CALL_P (insn)
+ && ((REG_P (reg) && REGNO (reg) < FIRST_PSEUDO_REGISTER
+ && overlaps_hard_reg_set_p (regs_invalidated_by_call,
+ GET_MODE (reg), REGNO (reg)))
+ || MEM_P (reg)
+ || find_reg_fusage (insn, CLOBBER, reg)))
+ return true;
+
return set_of (reg, insn) != NULL_RTX;
}
I haven't checked it, but maybe this also helps PR 56451 in some way.
Alternatively, we can just disable the *cbranch_t splitter after the
delay-branch pass:
Index: gcc/config/sh/sh.md
===================================================================
--- gcc/config/sh/sh.md (revision 218544)
+++ gcc/config/sh/sh.md (working copy)
@@ -8361,7 +8361,7 @@
{
return output_branch (sh_eval_treg_value (operands[1]), insn, operands);
}
- "&& 1"
+ "&& !crtl->dbr_scheduled_p"
[(set (pc) (if_then_else (eq (reg:SI T_REG) (match_dup 2))
(label_ref (match_dup 0))
(pc)))]
Both patches fix the problem here, but I haven't tested them further. My
feeling is that the function reg_set_p should be fixed.
