Re: [GCC][PATCH v2] arm: Add cde feature support for Cortex-M55 CPU.

[Richard Earnshaw via Gcc-patches]

On 31/10/2022 12:38, Srinath Parvathaneni via Gcc-patches wrote:
Hi,

-----Original Message-----
From: Christophe Lyon <christophe.l...@arm.com>
Sent: Monday, October 17, 2022 2:30 PM
To: Srinath Parvathaneni <srinath.parvathan...@arm.com>; gcc-
patc...@gcc.gnu.org
Cc: Richard Earnshaw <richard.earns...@arm.com>
Subject: Re: [GCC][PATCH] arm: Add cde feature support for Cortex-M55
CPU.

Hi Srinath,


On 10/10/22 10:20, Srinath Parvathaneni via Gcc-patches wrote:
Hi,

This patch adds cde feature (optional) support for Cortex-M55 CPU,
please refer [1] for more details. To use this feature we need to
specify +cdecpN (e.g. -mcpu=cortex-m55+cdecp<N>), where N is the
coprocessor number 0 to 7.

Bootstrapped for arm-none-linux-gnueabihf target, regression tested on
arm-none-eabi target and found no regressions.

[1] https://developer.arm.com/documentation/101051/0101/?lang=en
(version: r1p1).

Ok for master?

Regards,
Srinath.

gcc/ChangeLog:

2022-10-07  Srinath Parvathaneni  <srinath.parvathan...@arm.com>

          * common/config/arm/arm-common.cc (arm_canon_arch_option_1):
Ignore cde
          options for mlibarch.
          * config/arm/arm-cpus.in (begin cpu cortex-m55): Add cde options.
          * doc/invoke.texi (CDE): Document options for Cortex-M55 CPU.

gcc/testsuite/ChangeLog:

2022-10-07  Srinath Parvathaneni  <srinath.parvathan...@arm.com>

          * gcc.target/arm/multilib.exp: Add multilib tests for Cortex-M55 CPU.


###############     Attachment also inlined for ease of reply
###############


diff --git a/gcc/common/config/arm/arm-common.cc
b/gcc/common/config/arm/arm-common.cc
index

c38812f1ea6a690cd19b0dc74d963c4f5ae155ca..b6f955b3c012475f398382e72
c9a
3966412991ec 100644
--- a/gcc/common/config/arm/arm-common.cc
+++ b/gcc/common/config/arm/arm-common.cc
@@ -753,6 +753,15 @@ arm_canon_arch_option_1 (int argc, const char
**argv, bool arch_for_multilib)
         arm_initialize_isa (target_isa, selected_cpu->common.isa_bits);
         arm_parse_option_features (target_isa, &selected_cpu->common,
                                 strchr (cpu, '+'));
+      if (arch_for_multilib)
+       {
+         const enum isa_feature removable_bits[] =
{ISA_IGNORE_FOR_MULTILIB,
+                                                    isa_nobit};
+         sbitmap isa_bits = sbitmap_alloc (isa_num_bits);
+         arm_initialize_isa (isa_bits, removable_bits);
+         bitmap_and_compl (target_isa, target_isa, isa_bits);
+       }
+

I can see the piece of code you add here is exactly the same as the one a few
lines above when handling "if (arch)". Can this be moved below and thus be
common to the two cases, or does it have to be performed before
bitmap_ior of fpu_isa?

Thanks for pointing out this, I have moved the common code below the arch and 
cpu
if blocks in the attached patch.
  
Also, IIUC, CDE was already optional for other CPUs (M33, M35P, star-mc1),
so the hunk above fixes a latent bug when handling multilibs for these CPUs
too? If so, maybe worth splitting the patch into two parts since the above is
not strictly related to M55?

Even though CDE is optional for the mentioned CPUs as per the specs, the code to
enable CDE as optional feature is missing in current compiler.
Current GCC compiler supports CDE as optional feature only with -march options 
and
this pass adds CDE as optional for M55 and so this is not a fix bug.

But I'm not a maintainer ;-)

Thanks,

Christophe

         if (fpu && strcmp (fpu, "auto") != 0)
        {
          /* The easiest and safest way to remove the default fpu diff
--git a/gcc/config/arm/arm-cpus.in b/gcc/config/arm/arm-cpus.in index

5a63bc548e54dbfdce5d1df425bd615d81895d80..aa02c04c4924662f3ddd58e
69673
92ba3f4b4a87 100644
--- a/gcc/config/arm/arm-cpus.in
+++ b/gcc/config/arm/arm-cpus.in
@@ -1633,6 +1633,14 @@ begin cpu cortex-m55
    option nomve remove mve mve_float
    option nofp remove ALL_FP mve_float
    option nodsp remove MVE mve_float
+ option cdecp0 add cdecp0
+ option cdecp1 add cdecp1
+ option cdecp2 add cdecp2
+ option cdecp3 add cdecp3
+ option cdecp4 add cdecp4
+ option cdecp5 add cdecp5
+ option cdecp6 add cdecp6
+ option cdecp7 add cdecp7
    isa quirk_no_asmcpu quirk_vlldm
    costs v7m
    vendor 41
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index

aa5655764a0360959f9c1061749d2cc9ebd23489..26857f7a90e42d925bc69086
86ac
78138a53c4ad 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -21698,6 +21698,10 @@ floating-point instructions on @samp{cortex-
m55}.
   Disable the M-Profile Vector Extension (MVE) single precision floating-
point
   instructions on @samp{cortex-m55}.

+@item +cdecp0, +cdecp1, ... , +cdecp7 Enable the Custom Datapath
+Extension (CDE) on selected coprocessors according to the numbers
+given in the options in the range 0 to 7 on @samp{cortex-m55}.
+
   @item  +nofp
   Disables the floating-point instructions on @samp{arm9e},
   @samp{arm946e-s}, @samp{arm966e-s}, @samp{arm968e-s},
@samp{arm10e},
diff --git a/gcc/testsuite/gcc.target/arm/multilib.exp
b/gcc/testsuite/gcc.target/arm/multilib.exp
index

2fa648c61dafebb663969198bf7849400a7547f6..7a977bff58b7b68bfe9e49d7
6029
89a39caa6534 100644
--- a/gcc/testsuite/gcc.target/arm/multilib.exp
+++ b/gcc/testsuite/gcc.target/arm/multilib.exp
@@ -851,6 +851,18 @@ if {[multilib_config "rmprofile"] } {
        {-mcpu=cortex-m55+nomve+nofp -mfpu=auto -mfloat-abi=softfp}
"thumb/v8-m.main/nofp"
        {-mcpu=cortex-m55+nodsp+nofp -mfpu=auto -mfloat-abi=soft}
"thumb/v8-m.main/nofp"
        {-mcpu=cortex-m55+nodsp+nofp -mfpu=auto -mfloat-abi=softfp}
"thumb/v8-m.main/nofp"
+       {-mcpu=cortex-m55 -mfloat-abi=hard -mfpu=auto} "thumb/v8-
m.main+dp/hard"
+       {-mcpu=cortex-m55+cdecp0 -mfloat-abi=hard -mfpu=auto}
"thumb/v8-m.main+dp/hard"
+       {-mcpu=cortex-m55+nomve+cdecp0 -mfloat-abi=hard -mfpu=auto}
"thumb/v8-m.main+dp/hard"
+       {-mcpu=cortex-
m55+cdecp0+cdecp1+cdecp2+cdecp3+cdecp4+cdecp5+cdecp6+cdecp7 -
mfloat-abi=hard -mfpu=auto} "thumb/v8-m.main+dp/hard"
+       {-mcpu=cortex-m55 -mfloat-abi=softfp -mfpu=auto} "thumb/v8-
m.main+dp/softfp"
+       {-mcpu=cortex-m55+cdecp0 -mfloat-abi=softfp -mfpu=auto}
"thumb/v8-m.main+dp/softfp"
+       {-mcpu=cortex-m55+nomve+cdecp0 -mfloat-abi=softfp -mfpu=auto}
"thumb/v8-m.main+dp/softfp"
+       {-mcpu=cortex-
m55+cdecp0+cdecp1+cdecp2+cdecp3+cdecp4+cdecp5+cdecp6+cdecp7 -
mfloat-abi=softfp -mfpu=auto} "thumb/v8-m.main+dp/softfp"
+       {-mcpu=cortex-m55 -mfloat-abi=soft -mfpu=auto} "thumb/v8-
m.main/nofp"
+       {-mcpu=cortex-m55+cdecp0 -mfloat-abi=soft -mfpu=auto}
"thumb/v8-m.main/nofp"
+       {-mcpu=cortex-m55+nomve+cdecp0 -mfloat-abi=soft -mfpu=auto}
"thumb/v8-m.main/nofp"
+       {-mcpu=cortex-
m55+cdecp0+cdecp1+cdecp2+cdecp3+cdecp4+cdecp5+cdecp6+cdecp7 -
mfloat-abi=soft -mfpu=auto} "thumb/v8-m.main/nofp"
        {-march=armv8-m.main+cdecp0 -mfpu=auto -mfloat-abi=soft}
"thumb/v8-m.main/nofp"
        {-march=armv8-m.main+fp+cdecp0 -mfpu=auto -mfloat-abi=soft}
"thumb/v8-m.main/nofp"
        {-march=armv8-m.main+fp.dp+cdecp0 -mfpu=auto -mfloat-abi=soft}
"thumb/v8-m.main/nofp"




+  auto_sbitmap removable_isa (isa_num_bits);

Removable isn't a good description of this variable.  I think it would 
be better to use something closer to the ISA_IGNORE_FOR_MULTILIB macro 
that gets defined from arm-cpus.in:  perhaps 'ignore_multilib_isa'.

OK with that change.

R.