Re: [PATCH], V7, #7 of 7, Turn on -mpcrel for Linux 64-bit, but not for other targets

2019-11-26 Thread Segher Boessenkool 
On Thu, Nov 14, 2019 at 06:14:47PM -0500, Michael Meissner wrote:
>   * config/rs6000/linux64.h (TARGET_PREFIXED_ADDR_DEFAULT): Enable
>   prefixed addressing by default.
>   (TARGET_PCREL_DEFAULT): Enable pc-relative addressing by default.
>   * config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Only
>   enable -mprefixed-addr and -mpcrel if the OS tm.h says to enable
>   it.
>   (ADDRESSING_FUTURE_MASKS): New mask macro.
>   (OTHER_FUTURE_MASKS): Use ADDRESSING_FUTURE_MASKS.
>   * config/rs6000/rs6000.c (TARGET_PREFIXED_ADDR_DEFAULT): Do not
>   enable -mprefixed-addr unless the OS tm.h says to.
>   (TARGET_PCREL_DEFAULT): Do not enable -mpcrel unless the OS tm.h
>   says to.
>   (rs6000_option_override_internal): Do not enable -mprefixed-addr
>   or -mpcrel unless the OS tm.h says to enable it.  Add more checks
>   for -mcpu=future.

> +/* Support for a future processor's features.  The prefixed and pc-relative
> +   addressing bits are not added here.  Instead, rs6000.c adds them if the OS
> +   tm.h says that it supports the addressing modes.  */

This comment could be a lot clearer.  It should just say it is about
ADRESSING_FUTURE_MASKS, and not mention rs6000.c at all.

>  #define ISA_FUTURE_MASKS_SERVER  (ISA_3_0_MASKS_SERVER   
> \
> -  | OPTION_MASK_FUTURE   \
> +  | OPTION_MASK_FUTURE)
> +
> +/* Addressing related flags on a future processor.  These flags are broken 
> out
> +   because not all targets will support either pc-relative addressing, or 
> even
> +   prefixed addressing, and we want to clear all of the addressing bits
> +   on targets that cannot support prefixed/pcrel addressing.  */
> +#define ADDRESSING_FUTURE_MASKS  (OPTION_MASK_PCREL  
> \
>| OPTION_MASK_PREFIXED_ADDR)

> --- gcc/config/rs6000/rs6000.c(revision 278181)
> +++ gcc/config/rs6000/rs6000.c(working copy)
> @@ -98,6 +98,16 @@
>  #endif
>  #endif
>  
> +/* Set up the defaults for whether prefixed addressing is used, and if it is
> +   used, whether we want to turn on pc-relative support by default.  */
> +#ifndef TARGET_PREFIXED_ADDR_DEFAULT
> +#define TARGET_PREFIXED_ADDR_DEFAULT 0
> +#endif
> +
> +#ifndef TARGET_PCREL_DEFAULT
> +#define TARGET_PCREL_DEFAULT 0
> +#endif

"DEFAULT" is a bad name for this?  "SUPPORTED"?

We do *not* turn on prefixed or pcrel by default on most linux64 targets
-- most of those are p9 or p8 or p7 or older!  So "SUPPORTED" isn't good
either.  SUPPORTED_BY_OS?

A name like "XXX_DEFAULT" inevitably means we will later get an
"XXX_REALLY_DEFAULT" macro as well.  Not good.

> +  /* Enable prefixed addressing and pc-relative addressing on 64-bit ELF v2
> + systems if the OS tm.h file says that it is supported and the user did 
> not
> + explicitly use -mprefixed-addr or -mpcrel.  At the present time, only
> + 64-bit Linux enables this.


> +  /* Enable defaults if desired.  */

This comment does not say anything.  Please say something like "Enable
PCREL and PREFIXED if [...]"

> +  else
> + {
> +   if (!explicit_prefixed
> +   && (TARGET_PREFIXED_ADDR_DEFAULT
> +   || TARGET_PCREL
> +   || TARGET_PCREL_DEFAULT))
> + rs6000_isa_flags |= OPTION_MASK_PREFIXED_ADDR;
> +
> +   if (!explicit_pcrel && TARGET_PCREL_DEFAULT
> +   && TARGET_CMODEL == CMODEL_MEDIUM)
> + rs6000_isa_flags |= OPTION_MASK_PCREL;
> + }
> +}

... and I don't understand this code.  If you use -mpcrel but you do not
have the medium model, you _do_ get prefixed but you do _not_ get pcrel?
And this all quietly?


Segher

[PATCH], V7, #7 of 7, Turn on -mpcrel for Linux 64-bit, but not for other targets

2019-11-14 Thread Michael Meissner 
This patch will enable prefixed addressing and PC-relative addressing if the OS
target support indicates that the OS supports either prefixed addressing and
whether it supports PC-relative addressing when the user uses -mcpu=future.  At
the moment, 64-bit Linux is the only system that enables both prefixed
addressing and PC-relative addressing.

I have built bootstrap compilers with this patch and there were no regressions
in the testsuite.  In addition, during development, I set each of the two
options, and built a copiler with it, and I observed that the expected behavior
for the default of whether prefixed addressing an PC-relative support is
enabled.  Can I check this into the FSF trunk?

2019-11-14  Michael Meissner  

* config/rs6000/linux64.h (TARGET_PREFIXED_ADDR_DEFAULT): Enable
prefixed addressing by default.
(TARGET_PCREL_DEFAULT): Enable pc-relative addressing by default.
* config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Only
enable -mprefixed-addr and -mpcrel if the OS tm.h says to enable
it.
(ADDRESSING_FUTURE_MASKS): New mask macro.
(OTHER_FUTURE_MASKS): Use ADDRESSING_FUTURE_MASKS.
* config/rs6000/rs6000.c (TARGET_PREFIXED_ADDR_DEFAULT): Do not
enable -mprefixed-addr unless the OS tm.h says to.
(TARGET_PCREL_DEFAULT): Do not enable -mpcrel unless the OS tm.h
says to.
(rs6000_option_override_internal): Do not enable -mprefixed-addr
or -mpcrel unless the OS tm.h says to enable it.  Add more checks
for -mcpu=future.

Index: gcc/config/rs6000/linux64.h
===
--- gcc/config/rs6000/linux64.h (revision 278173)
+++ gcc/config/rs6000/linux64.h (working copy)
@@ -640,3 +640,11 @@ extern int dot_symbols;
enabling the __float128 keyword.  */
 #undef TARGET_FLOAT128_ENABLE_TYPE
 #define TARGET_FLOAT128_ENABLE_TYPE 1
+
+/* Enable support for pc-relative and numeric prefixed addressing on the
+   'future' system.  */
+#undef  TARGET_PREFIXED_ADDR_DEFAULT
+#define TARGET_PREFIXED_ADDR_DEFAULT   1
+
+#undef  TARGET_PCREL_DEFAULT
+#define TARGET_PCREL_DEFAULT   1
Index: gcc/config/rs6000/rs6000-cpus.def
===
--- gcc/config/rs6000/rs6000-cpus.def   (revision 278173)
+++ gcc/config/rs6000/rs6000-cpus.def   (working copy)
@@ -75,15 +75,21 @@
 | OPTION_MASK_P8_VECTOR\
 | OPTION_MASK_P9_VECTOR)
 
-/* Support for a future processor's features.  Do not enable -mpcrel until it
-   is fully functional.  */
+/* Support for a future processor's features.  The prefixed and pc-relative
+   addressing bits are not added here.  Instead, rs6000.c adds them if the OS
+   tm.h says that it supports the addressing modes.  */
 #define ISA_FUTURE_MASKS_SERVER(ISA_3_0_MASKS_SERVER   
\
-| OPTION_MASK_FUTURE   \
+| OPTION_MASK_FUTURE)
+
+/* Addressing related flags on a future processor.  These flags are broken out
+   because not all targets will support either pc-relative addressing, or even
+   prefixed addressing, and we want to clear all of the addressing bits
+   on targets that cannot support prefixed/pcrel addressing.  */
+#define ADDRESSING_FUTURE_MASKS(OPTION_MASK_PCREL  
\
 | OPTION_MASK_PREFIXED_ADDR)
 
 /* Flags that need to be turned off if -mno-future.  */
-#define OTHER_FUTURE_MASKS (OPTION_MASK_PCREL  \
-| OPTION_MASK_PREFIXED_ADDR)
+#define OTHER_FUTURE_MASKS ADDRESSING_FUTURE_MASKS
 
 /* Flags that need to be turned off if -mno-power9-vector.  */
 #define OTHER_P9_VECTOR_MASKS  (OPTION_MASK_FLOAT128_HW\
Index: gcc/config/rs6000/rs6000.c
===
--- gcc/config/rs6000/rs6000.c  (revision 278181)
+++ gcc/config/rs6000/rs6000.c  (working copy)
@@ -98,6 +98,16 @@
 #endif
 #endif
 
+/* Set up the defaults for whether prefixed addressing is used, and if it is
+   used, whether we want to turn on pc-relative support by default.  */
+#ifndef TARGET_PREFIXED_ADDR_DEFAULT
+#define TARGET_PREFIXED_ADDR_DEFAULT   0
+#endif
+
+#ifndef TARGET_PCREL_DEFAULT
+#define TARGET_PCREL_DEFAULT   0
+#endif
+
 /* Support targetm.vectorize.builtin_mask_for_load.  */
 GTY(()) tree altivec_builtin_mask_for_load;
 
@@ -2535,6 +2545,14 @@ rs6000_debug_reg_global (void)
   if (TARGET_DIRECT_MOVE_128)
 fprintf (stderr, DEBUG_FMT_D, "VSX easy 64-bit mfvsrld element",
 (int)VECTOR_ELEMENT_MFVSRLD_64BIT);
+
+  if (TARGET_FUTURE)
+{
+  fprintf (stderr, DEBUG_FMT_D, "TARGET_PREFIXED_ADDR_DEFAULT",
+  TARGET_PREFIXED_ADDR_DEFAULT);
+  fprintf (stderr, DEBUG_FMT_D, "TAR