@@ -348,6 +348,18 @@ private:
extern sh_treg_insns sh_split_treg_set_expr (rtx x, rtx_insn* curr_insn);
+enum
+{
+ /* An effective conditional branch distance of zero bytes is impossible.
+ Hence we can use it to designate an unknown value. */
+ unknown_cbranch_distance = 0u,
+ infinite_cbranch_distance = ~0u
+};
+
+unsigned int
+sh_cbranch_distance (rtx_insn* cbranch_insn,
+ unsigned int max_dist = infinite_cbranch_distance);
+
#endif /* RTX_CODE */
extern void sh_cpu_cpp_builtins (cpp_reader* pfile);
@@ -1928,6 +1928,52 @@ sh_fixed_condition_code_regs (unsigned int* p1, unsigned int* p2)
return true;
}
+/* Try to calculate the branch distance of a conditional branch in bytes.
+
+ FIXME: Because of PR 59189 we can't use the CFG here. Instead just
+ walk from this insn into the next (fall-through) basic block and see if
+ we hit the label. */
+unsigned int
+sh_cbranch_distance (rtx_insn* _cbranch_insn, unsigned int max_dist)
+{
+ rtx_jump_insn* cbranch_insn = safe_as_a<rtx_jump_insn*> (_cbranch_insn);
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "sh_cbranch_distance insn = \n");
+ print_rtl_single (dump_file, cbranch_insn);
+ }
+
+ unsigned int dist = 0;
+
+ for (rtx_insn* i = next_nonnote_insn (cbranch_insn);
+ i != NULL && dist < max_dist; i = next_nonnote_insn (i))
+ {
+ const unsigned int i_len = get_attr_length (i);
+ dist += i_len;
+
+ if (dump_file)
+ fprintf (dump_file, " insn %d length = %u dist = %u\n",
+ INSN_UID (i), i_len, dist);
+
+ if (rtx_code_label* l = dyn_cast<rtx_code_label*> (i))
+ {
+ if (l == cbranch_insn->jump_target ())
+ {
+ if (dump_file)
+ fprintf (dump_file, " cbranch dist = %u\n", dist);
+ return dist;
+ }
+ break;
+ }
+ }
+
+ if (dump_file)
+ fprintf (dump_file, " cbranch dist = unknown\n");
+
+ return unknown_cbranch_distance;
+}
+
enum rtx_code
prepare_cbranch_operands (rtx *operands, machine_mode mode,
enum rtx_code comparison)
@@ -477,16 +477,6 @@
(define_attr "is_sfunc" ""
(if_then_else (eq_attr "type" "sfunc") (const_int 1) (const_int 0)))
-(define_attr "branch_zero" "yes,no"
- (cond [(eq_attr "type" "!cbranch") (const_string "no")
- (ne (symbol_ref "(next_active_insn (insn)\
- == (prev_active_insn\
- (XEXP (SET_SRC (PATTERN (insn)), 1))))\
- && get_attr_length (next_active_insn (insn)) == 2")
- (const_int 0))
- (const_string "yes")]
- (const_string "no")))
-
;; SH4 Double-precision computation with double-precision result -
;; the two halves are ready at different times.
(define_attr "dfp_comp" "yes,no"
@@ -539,8 +529,13 @@
(eq_attr "type" "!pstore,prget")) (nil) (nil)])
;; Conditional branches with delay slots are available starting with SH2.
+;; If zero displacement conditional branches are fast, disable the delay
+;; slot if the branch jumps over only one 2-byte insn.
(define_delay
- (and (eq_attr "type" "cbranch") (match_test "TARGET_SH2"))
+ (and (eq_attr "type" "cbranch")
+ (match_test "TARGET_SH2")
+ (not (and (match_test "TARGET_ZDCBRANCH")
+ (match_test "sh_cbranch_distance (insn, 4) == 2"))))
[(eq_attr "cond_delay_slot" "yes") (nil) (nil)])
;; -------------------------------------------------------------------------
Hi, On SH a conditional branch with a (physical) zero displacement jumps over the next instruction. On some SH hardware implementations these branches are handled in a special way which allows using it for conditional execution. A while ago I've added some hardcoded asm patterns to utilize this. It seems there has been an attempt to do something about it a long time ago with the "branch_zero" attribute. However I could not find any uses thereof and wasn't sure how to utilize it. The attached patch disables the delay slot (for the DBR pass) of conditional branches which branch over only one 2-byte instruction. This results in more zero-displacement branches to be emitted. Having this in place, it would also be possible to simplify those hardcoded asm patterns (e.g. SH abs patterns). However, while that works, doing so exposes the actual CFG to other passes and in quite some cases basic blocks get reordered in a very counterproductive way resulting in worse code. Tested on sh-elf with make -k check RUNTESTFLAGS="--target_board=sh-sim\{-m2/-ml,-m2/-mb, -m2a/-mb,-m4/-ml,-m4/-mb,-m4a/-ml,-m4a/-mb}" Committed as r235993. Cheers, Oleg gcc/ChangeLog: * config/sh/sh-protos.h (sh_cbranch_distance): Declare new function. * config/sh/sh.c (sh_cbranch_distance): Implement it. * config/sh/sh.md (branch_zero): Remove define_attr. (define_delay): Disable delay slot if branch distance is one insn.