diff mbox series

[1/3] MIPS: add -mcompact-branches=prefer option

Message ID 20210205095338.28231-1-yunqiang.su@cipunited.com
State New
Headers show
Series [1/3] MIPS: add -mcompact-branches=prefer option | expand

Commit Message

YunQiang Su Feb. 5, 2021, 9:53 a.m. UTC 
For MIPSr6, we may wish to use compact-branches only.
Currently, we have to use `always' option, while it is mark as conflict
with pre-R6.
  cc1: error: unsupported combination: ‘mips32r2’ -mcompact-branches=always

It make some trouble for distributions to make -mcompact-branches=always
default for R6 only.

The new added `prefer' option:
   just ignored by pre-R6 target.
   do the same as `always' for R6+.
---
 gcc/config/mips/mips-opts.h                        |  3 ++-
 gcc/config/mips/mips.h                             |  6 ++++--
 gcc/config/mips/mips.opt                           |  3 +++
 gcc/doc/invoke.texi                                |  6 ++++++
 gcc/testsuite/gcc.target/mips/compact-branches-8.c | 10 ++++++++++
 gcc/testsuite/gcc.target/mips/compact-branches-9.c | 10 ++++++++++
 6 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/mips/compact-branches-8.c
 create mode 100644 gcc/testsuite/gcc.target/mips/compact-branches-9.c

Comments

Jeff Law Feb. 16, 2021, 7:18 p.m. UTC | #1 
On 2/5/21 2:53 AM, YunQiang Su wrote:
> For MIPSr6, we may wish to use compact-branches only.
> Currently, we have to use `always' option, while it is mark as conflict
> with pre-R6.
>   cc1: error: unsupported combination: ‘mips32r2’ -mcompact-branches=always
>
> It make some trouble for distributions to make -mcompact-branches=always
> default for R6 only.
>
> The new added `prefer' option:
>    just ignored by pre-R6 target.
>    do the same as `always' for R6+.
> ---
>  gcc/config/mips/mips-opts.h                        |  3 ++-
>  gcc/config/mips/mips.h                             |  6 ++++--
>  gcc/config/mips/mips.opt                           |  3 +++
>  gcc/doc/invoke.texi                                |  6 ++++++
>  gcc/testsuite/gcc.target/mips/compact-branches-8.c | 10 ++++++++++
>  gcc/testsuite/gcc.target/mips/compact-branches-9.c | 10 ++++++++++
>  6 files changed, 35 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/mips/compact-branches-8.c
>  create mode 100644 gcc/testsuite/gcc.target/mips/compact-branches-9.c
I think this will be OK once the wording in patch 2/3 of this series is
fixed.

It would be helpful if you could also include a ChangeLog entry.

Jeff
Maciej W. Rozycki Feb. 16, 2021, 7:41 p.m. UTC | #2 
On Tue, 16 Feb 2021, Jeff Law via Gcc-patches wrote:

> I think this will be OK once the wording in patch 2/3 of this series is
> fixed.

 As I noted with 2/3 I would like to know what this extra complication is 
exactly needed for, and then whether we can't reuse the existing options.  
Once settled I think it would best be placed in the change description for 
posterity, so that discussions do not have to be chased like I had to with 
the original change (when we had a different policy on commit messages).

  Maciej
diff mbox series

Patch

diff --git a/gcc/config/mips/mips-opts.h b/gcc/config/mips/mips-opts.h
index 6214849f3e1..f3804b9722b 100644
--- a/gcc/config/mips/mips-opts.h
+++ b/gcc/config/mips/mips-opts.h
@@ -51,6 +51,7 @@  enum mips_r10k_cache_barrier_setting {
 enum mips_cb_setting {
   MIPS_CB_NEVER,
   MIPS_CB_OPTIMAL,
-  MIPS_CB_ALWAYS
+  MIPS_CB_ALWAYS,
+  MIPS_CB_PREFER
 };
 #endif
diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h
index b4a60a55d80..f8762fe6638 100644
--- a/gcc/config/mips/mips.h
+++ b/gcc/config/mips/mips.h
@@ -106,20 +106,22 @@  struct mips_cpu_info {
    'never' policy or the 'optimal' policy on a core that lacks
    compact branch instructions.  */
 #define TARGET_CB_NEVER (mips_cb == MIPS_CB_NEVER	\
-			 || (mips_cb == MIPS_CB_OPTIMAL \
+			 || ((mips_cb == MIPS_CB_OPTIMAL || mips_cb == MIPS_CB_PREFER) \
 			     && !ISA_HAS_COMPACT_BRANCHES))
 
 /* Compact branches may be used if the user either selects the
    'always' policy or the 'optimal' policy on a core that supports
    compact branch instructions.  */
 #define TARGET_CB_MAYBE (TARGET_CB_ALWAYS		\
-			 || (mips_cb == MIPS_CB_OPTIMAL \
+			 || ((mips_cb == MIPS_CB_OPTIMAL || mips_cb == MIPS_CB_PREFER) \
 			     && ISA_HAS_COMPACT_BRANCHES))
 
 /* Compact branches must always be generated if the user selects
    the 'always' policy or the 'optimal' policy om a core that
    lacks delay slot branch instructions.  */
 #define TARGET_CB_ALWAYS (mips_cb == MIPS_CB_ALWAYS	\
+			 || (mips_cb == MIPS_CB_PREFER \
+			     && ISA_HAS_COMPACT_BRANCHES)   \
 			 || (mips_cb == MIPS_CB_OPTIMAL \
 			     && !ISA_HAS_DELAY_SLOTS))
 
diff --git a/gcc/config/mips/mips.opt b/gcc/config/mips/mips.opt
index 6af8037e9bd..f2d7550e36c 100644
--- a/gcc/config/mips/mips.opt
+++ b/gcc/config/mips/mips.opt
@@ -464,6 +464,9 @@  Enum(mips_cb_setting) String(optimal) Value(MIPS_CB_OPTIMAL)
 EnumValue
 Enum(mips_cb_setting) String(always) Value(MIPS_CB_ALWAYS)
 
+EnumValue
+Enum(mips_cb_setting) String(prefer) Value(MIPS_CB_PREFER)
+
 mloongson-mmi
 Target Mask(LOONGSON_MMI)
 Use Loongson MultiMedia extensions Instructions (MMI) instructions.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3751bc3ac7c..9493c508d5b 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -25199,9 +25199,11 @@  and MIPS64 architectures specifically deprecate their use.
 @item -mcompact-branches=never
 @itemx -mcompact-branches=optimal
 @itemx -mcompact-branches=always
+@itemx -mcompact-branches=prefer
 @opindex mcompact-branches=never
 @opindex mcompact-branches=optimal
 @opindex mcompact-branches=always
+@opindex mcompact-branches=prefer
 These options control which form of branches will be generated.  The
 default is @option{-mcompact-branches=optimal}.
 
@@ -25215,6 +25217,10 @@  used instead.
 
 This option is supported from MIPS Release 6 onwards.
 
+The @option{-mcompact-branches=prefer} option is same with
+@option{-mcompact-branches=always} for MIPS Release 6 onwards, and
+is same with @option{-mcompact-branches=never} for pre-R6.
+
 The @option{-mcompact-branches=optimal} option will cause a delay slot
 branch to be used if one is available in the current ISA and the delay
 slot is successfully filled.  If the delay slot is not filled, a compact
diff --git a/gcc/testsuite/gcc.target/mips/compact-branches-8.c b/gcc/testsuite/gcc.target/mips/compact-branches-8.c
new file mode 100644
index 00000000000..72ffcb49cfc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/compact-branches-8.c
@@ -0,0 +1,10 @@ 
+/* { dg-options "-mno-abicalls -mcompact-branches=prefer isa_rev<=5" } */
+void bar (int);
+
+void
+foo ()
+{
+  bar (1);
+}
+
+/* { dg-final { scan-assembler "\t(j|jal)\t" } } */
diff --git a/gcc/testsuite/gcc.target/mips/compact-branches-9.c b/gcc/testsuite/gcc.target/mips/compact-branches-9.c
new file mode 100644
index 00000000000..7a46b53d3e4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/compact-branches-9.c
@@ -0,0 +1,10 @@ 
+/* { dg-options "-mno-abicalls -fno-PIC -mcompact-branches=prefer isa_rev>=6" } */
+void bar (int);
+
+void
+foo ()
+{
+  bar (1);
+}
+
+/* { dg-final { scan-assembler "\t(bc|balc)\t" } } */