[Bug target/52898] SH Target: Inefficient DImode comparisons

[olegendo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52898

--- Comment #7 from Oleg Endo <olegendo at gcc dot gnu.org> ---
Kaz, I'd like to deprecate the mcbranchdi and mcmpeqdi options in 4.9 and make
the current default values fixed as follows:

mcbranchdi is usually enabled (it gets disabled in some SH5 case in
sh_option_override).
mcmpeqdi is always disabled.

As a side effect, it would also "fix" PR 51697 (mcbranchdi will not be disabled
for -Os).

Are you OK with the following patch for 4.9?

Index: gcc/common/config/sh/sh-common.c
===================================================================
--- gcc/common/config/sh/sh-common.c    (revision 205756)
+++ gcc/common/config/sh/sh-common.c    (working copy)
@@ -34,7 +34,6 @@
     { OPT_LEVELS_1_PLUS_SPEED_ONLY, OPT_mdiv_, "inv:minlat", 1 },
     { OPT_LEVELS_SIZE, OPT_mdiv_, SH_DIV_STR_FOR_SIZE, 1 },
     { OPT_LEVELS_0_ONLY, OPT_mdiv_, "", 1 },
-    { OPT_LEVELS_SIZE, OPT_mcbranchdi, NULL, 0 },
     /* We can't meaningfully test TARGET_SHMEDIA here, because -m
        options haven't been parsed yet, hence we'd read only the
        default.  sh_target_reg_class will return NO_REGS if this is
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi    (revision 205756)
+++ gcc/doc/invoke.texi    (working copy)
@@ -959,7 +959,7 @@
 -mindexed-addressing -mgettrcost=@var{number} -mpt-fixed @gol
 -maccumulate-outgoing-args -minvalid-symbols @gol
 -matomic-model=@var{atomic-model} @gol
--mbranch-cost=@var{num} -mzdcbranch -mno-zdcbranch -mcbranchdi -mcmpeqdi @gol
+-mbranch-cost=@var{num} -mzdcbranch -mno-zdcbranch @gol
 -mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra @gol
 -mpretend-cmove -mtas}

@@ -20252,15 +20252,6 @@
 enabled by default when generating code for SH4 and SH4A.  It can be
explicitly
 disabled by specifying @option{-mno-zdcbranch}.

-@item -mcbranchdi
-@opindex mcbranchdi
-Enable the @code{cbranchdi4} instruction pattern.
-
-@item -mcmpeqdi
-@opindex mcmpeqdi
-Emit the @code{cmpeqdi_t} instruction pattern even when @option{-mcbranchdi}
-is in effect.
-
 @item -mfused-madd
 @itemx -mno-fused-madd
 @opindex mfused-madd
Index: gcc/config/sh/sh.opt
===================================================================
--- gcc/config/sh/sh.opt    (revision 205756)
+++ gcc/config/sh/sh.opt    (working copy)
@@ -233,11 +233,11 @@
 Assume that zero displacement conditional branches are fast

 mcbranchdi
-Target Var(TARGET_CBRANCHDI4)
+Target Undocumented Var(TARGET_CBRANCHDI4) Warn(%qs is deprecated and has no
effect)
 Enable cbranchdi4 pattern

 mcmpeqdi
-Target Var(TARGET_CMPEQDI_T)
+Target Undocumented Var(TARGET_CMPEQDI_T) Warn(%qs is deprecated and has no
effect)
 Emit cmpeqdi_t pattern even when -mcbranchdi is in effect.

 mcut2-workaround
Index: gcc/config/sh/sh.c
===================================================================
--- gcc/config/sh/sh.c    (revision 205756)
+++ gcc/config/sh/sh.c    (working copy)
@@ -771,6 +771,11 @@
   SUBTARGET_OVERRIDE_OPTIONS;
   if (optimize > 1 && !optimize_size)
     target_flags |= MASK_SAVE_ALL_TARGET_REGS;
+
+  /* Set default values of TARGET_CBRANCHDI4 and TARGET_CMPEQDI_T.  */
+  TARGET_CBRANCHDI4 = 1;
+  TARGET_CMPEQDI_T = 0;
+
   sh_cpu = PROCESSOR_SH1;
   assembler_dialect = 0;
   if (TARGET_SH2)