| Message ID | 20171021130958.GA29672@ibm-tiger.the-meissners.org |
|---|---|
| State | New |
| Headers | show |
| Series | , Enable IBM/IEEE long double format to overriden more easily | expand |
Hi Mike, On Sat, Oct 21, 2017 at 09:09:58AM -0400, Michael Meissner wrote: > As Segher and I were discussing off-line, I have some problems with the current > -mabi={ieee,ibm}longdouble switches as we start to planning to modify GCC 9 and > GLIBC 2.27/2.28 to support __float128 as the default long double format for > power server systems. > > My gripes are: > > 1) Using Warn() in rs6000.opt means that you get two warning messages when > you use the switches (one from the driver, and one from cc1). > > 2) I feel you should not get a warning if you select the option that > reflects the current default behavior (i.e. -mabi=ibmlongdouble > currently for power server systems). > > 3) There is no way to silenece the warning (i.e. -w doesn't work on > warnings in the .opt file). Both GLIBC and LIBGCC will need the > ability to build support modules with an explicit long double format. > > 4) In the future we will need a little more flexibility in how the default > is set. > > 5) There is a mis-match between the documentation and rs6000.opt, as these > switches are documented, but use Undocumented in the rs6000.opt. Agreed on all. > These patches fix these issues. If you use -Wno-psabi, it will silence the > warning. I have built these patches on a little endian power8 system, and > there were no regressions. Can I check these patches into the trunk? > > 2017-10-21 Michael Meissner <meissner@linux.vnet.ibm.com> > > * config/rs6000/aix.h (TARGET_IEEEQUAD_DEFAULT): Set long double > default to IBM. > * config/rs6000/darwin.h (TARGET_IEEEQUAD_DEFAULT): Likewise. > * config/rs6000/rs6000.opt (-mabi=ieeelongdouble): Move the > warning to rs6000.c. Remove the Undocumented flag, since it has > been documented. > (-mabi=ibmlongdouble): Likewise. And more importantly, we _want_ it to be documented (right)? > --- gcc/config/rs6000/rs6000.opt (revision 253961) > +++ gcc/config/rs6000/rs6000.opt (working copy) > @@ -381,10 +381,10 @@ mabi=d32 > Target RejectNegative Undocumented Warn(using old darwin ABI) Var(rs6000_darwin64_abi, 0) > > mabi=ieeelongdouble > -Target RejectNegative Undocumented Warn(using IEEE extended precision long double) Var(rs6000_ieeequad) Save > +Target RejectNegative Var(rs6000_ieeequad) Save > > mabi=ibmlongdouble > -Target RejectNegative Undocumented Warn(using IBM extended precision long double) Var(rs6000_ieeequad, 0) > +Target RejectNegative Var(rs6000_ieeequad, 0) Does this need "Save" as well? > + if (!warned_change_long_double && warn_psabi) > + { > + warned_change_long_double = true; > + if (TARGET_IEEEQUAD) > + warning (0, "Using IEEE extended precision long double"); > + else > + warning (0, "Using IBM extended precision long double"); > + } You can put OPT_Wpsabi in place of that 0, it's what that arg is for :-) Okay with that changed. Thanks! Segher
On Wed, Oct 25, 2017 at 07:11:07PM -0500, Segher Boessenkool wrote: > Hi Mike, > > On Sat, Oct 21, 2017 at 09:09:58AM -0400, Michael Meissner wrote: > > As Segher and I were discussing off-line, I have some problems with the current > > -mabi={ieee,ibm}longdouble switches as we start to planning to modify GCC 9 and > > GLIBC 2.27/2.28 to support __float128 as the default long double format for > > power server systems. > > > > My gripes are: > > > > 1) Using Warn() in rs6000.opt means that you get two warning messages when > > you use the switches (one from the driver, and one from cc1). > > > > 2) I feel you should not get a warning if you select the option that > > reflects the current default behavior (i.e. -mabi=ibmlongdouble > > currently for power server systems). > > > > 3) There is no way to silenece the warning (i.e. -w doesn't work on > > warnings in the .opt file). Both GLIBC and LIBGCC will need the > > ability to build support modules with an explicit long double format. > > > > 4) In the future we will need a little more flexibility in how the default > > is set. > > > > 5) There is a mis-match between the documentation and rs6000.opt, as these > > switches are documented, but use Undocumented in the rs6000.opt. > > Agreed on all. > > > These patches fix these issues. If you use -Wno-psabi, it will silence the > > warning. I have built these patches on a little endian power8 system, and > > there were no regressions. Can I check these patches into the trunk? > > > > 2017-10-21 Michael Meissner <meissner@linux.vnet.ibm.com> > > > > * config/rs6000/aix.h (TARGET_IEEEQUAD_DEFAULT): Set long double > > default to IBM. > > * config/rs6000/darwin.h (TARGET_IEEEQUAD_DEFAULT): Likewise. > > * config/rs6000/rs6000.opt (-mabi=ieeelongdouble): Move the > > warning to rs6000.c. Remove the Undocumented flag, since it has > > been documented. > > (-mabi=ibmlongdouble): Likewise. > > And more importantly, we _want_ it to be documented (right)? I would have preferred to not document it until GCC 9 when we start the switch to long double == _Float128, but since it was already documented (albeit only for 32 bit), I kept it documented. If you want me to change it to undocumented, I can do that. > > --- gcc/config/rs6000/rs6000.opt (revision 253961) > > +++ gcc/config/rs6000/rs6000.opt (working copy) > > @@ -381,10 +381,10 @@ mabi=d32 > > Target RejectNegative Undocumented Warn(using old darwin ABI) Var(rs6000_darwin64_abi, 0) > > > > mabi=ieeelongdouble > > -Target RejectNegative Undocumented Warn(using IEEE extended precision long double) Var(rs6000_ieeequad) Save > > +Target RejectNegative Var(rs6000_ieeequad) Save > > > > mabi=ibmlongdouble > > -Target RejectNegative Undocumented Warn(using IBM extended precision long double) Var(rs6000_ieeequad, 0) > > +Target RejectNegative Var(rs6000_ieeequad, 0) > > Does this need "Save" as well? No for variables, you want Save on the first instance only. > > + if (!warned_change_long_double && warn_psabi) > > + { > > + warned_change_long_double = true; > > + if (TARGET_IEEEQUAD) > > + warning (0, "Using IEEE extended precision long double"); > > + else > > + warning (0, "Using IBM extended precision long double"); > > + } > > You can put OPT_Wpsabi in place of that 0, it's what that arg is for :-) Ah, ok. Thanks. > Okay with that changed. Thanks! > > > Segher >
Index: gcc/config/rs6000/aix.h =================================================================== --- gcc/config/rs6000/aix.h (revision 253961) +++ gcc/config/rs6000/aix.h (working copy) @@ -78,6 +78,9 @@ #undef TARGET_IEEEQUAD #define TARGET_IEEEQUAD 0 +#undef TARGET_IEEEQUAD_DEFAULT +#define TARGET_IEEEQUAD_DEFAULT 0 + /* The AIX linker will discard static constructors in object files before collect has a chance to see them, so scan the object files directly. */ #define COLLECT_EXPORT_LIST Index: gcc/config/rs6000/rs6000.opt =================================================================== --- gcc/config/rs6000/rs6000.opt (revision 253961) +++ gcc/config/rs6000/rs6000.opt (working copy) @@ -381,10 +381,10 @@ mabi=d32 Target RejectNegative Undocumented Warn(using old darwin ABI) Var(rs6000_darwin64_abi, 0) mabi=ieeelongdouble -Target RejectNegative Undocumented Warn(using IEEE extended precision long double) Var(rs6000_ieeequad) Save +Target RejectNegative Var(rs6000_ieeequad) Save mabi=ibmlongdouble -Target RejectNegative Undocumented Warn(using IBM extended precision long double) Var(rs6000_ieeequad, 0) +Target RejectNegative Var(rs6000_ieeequad, 0) mcpu= Target RejectNegative Joined Var(rs6000_cpu_index) Init(-1) Enum(rs6000_cpu_opt_value) Save Index: gcc/config/rs6000/darwin.h =================================================================== --- gcc/config/rs6000/darwin.h (revision 253961) +++ gcc/config/rs6000/darwin.h (working copy) @@ -274,6 +274,9 @@ extern int darwin_emit_branch_islands; #undef TARGET_IEEEQUAD #define TARGET_IEEEQUAD 0 +#undef TARGET_IEEEQUAD_DEFAULT +#define TARGET_IEEEQUAD_DEFAULT 0 + /* Since Darwin doesn't do TOCs, stub this out. */ #define ASM_OUTPUT_SPECIAL_POOL_ENTRY_P(X, MODE) ((void)X, (void)MODE, 0) Index: gcc/config/rs6000/rs6000.c =================================================================== --- gcc/config/rs6000/rs6000.c (revision 253961) +++ gcc/config/rs6000/rs6000.c (working copy) @@ -86,6 +86,20 @@ #define TARGET_NO_PROTOTYPE 0 #endif + /* Set -mabi=ieeelongdouble on some old targets. In the future, power server + systems will also set long double to be IEEE 128-bit. AIX and Darwin + explicitly redefine TARGET_IEEEQUAD and TARGET_IEEEQUAD_DEFAULT to 0, so + those systems will not pick up this default. This needs to be after all + of the include files, so that POWERPC_LINUX and POWERPC_FREEBSD are + properly defined. */ +#ifndef TARGET_IEEEQUAD_DEFAULT +#if !defined (POWERPC_LINUX) && !defined (POWERPC_FREEBSD) +#define TARGET_IEEEQUAD_DEFAULT 1 +#else +#define TARGET_IEEEQUAD_DEFAULT 0 +#endif +#endif + #define min(A,B) ((A) < (B) ? (A) : (B)) #define max(A,B) ((A) > (B) ? (A) : (B)) @@ -2875,6 +2889,13 @@ rs6000_debug_reg_global (void) fprintf (stderr, DEBUG_FMT_D, "tls_size", rs6000_tls_size); fprintf (stderr, DEBUG_FMT_D, "long_double_size", rs6000_long_double_type_size); + if (rs6000_long_double_type_size == 128) + { + fprintf (stderr, DEBUG_FMT_S, "long double type", + TARGET_IEEEQUAD ? "IEEE" : "IBM"); + fprintf (stderr, DEBUG_FMT_S, "default long double type", + TARGET_IEEEQUAD_DEFAULT ? "IEEE" : "IBM"); + } fprintf (stderr, DEBUG_FMT_D, "sched_restricted_insns_priority", (int)rs6000_sched_restricted_insns_priority); fprintf (stderr, DEBUG_FMT_D, "Number of standard builtins", @@ -4557,13 +4578,26 @@ rs6000_option_override_internal (bool gl rs6000_long_double_type_size = RS6000_DEFAULT_LONG_DOUBLE_SIZE; } - /* Set -mabi=ieeelongdouble on some old targets. Note, AIX and Darwin - explicitly redefine TARGET_IEEEQUAD to 0, so those systems will not - pick up this default. */ -#if !defined (POWERPC_LINUX) && !defined (POWERPC_FREEBSD) + /* Set -mabi=ieeelongdouble on some old targets. In the future, power server + systems will also set long double to be IEEE 128-bit. AIX and Darwin + explicitly redefine TARGET_IEEEQUAD and TARGET_IEEEQUAD_DEFAULT to 0, so + those systems will not pick up this default. Warn if the user changes the + default unless -Wno-psabi. */ if (!global_options_set.x_rs6000_ieeequad) - rs6000_ieeequad = 1; -#endif + rs6000_ieeequad = TARGET_IEEEQUAD_DEFAULT; + + else if (rs6000_ieeequad != TARGET_IEEEQUAD_DEFAULT && TARGET_LONG_DOUBLE_128) + { + static bool warned_change_long_double; + if (!warned_change_long_double && warn_psabi) + { + warned_change_long_double = true; + if (TARGET_IEEEQUAD) + warning (0, "Using IEEE extended precision long double"); + else + warning (0, "Using IBM extended precision long double"); + } + } /* Enable the default support for IEEE 128-bit floating point on Linux VSX sytems. In GCC 7, we would enable the the IEEE 128-bit floating point Index: gcc/doc/invoke.texi =================================================================== --- gcc/doc/invoke.texi (revision 253961) +++ gcc/doc/invoke.texi (working copy) @@ -22607,12 +22607,14 @@ Disable Book-E SPE ABI extensions for th @item -mabi=ibmlongdouble @opindex mabi=ibmlongdouble Change the current ABI to use IBM extended-precision long double. -This is a PowerPC 32-bit SYSV ABI option. +This is not likely to work if your system defaults to using IEEE +extended-precision long double. @item -mabi=ieeelongdouble @opindex mabi=ieeelongdouble Change the current ABI to use IEEE extended-precision long double. -This is a PowerPC 32-bit Linux ABI option. +This is not likely to work if your system defaults to using IBM +extended-precision long double. @item -mabi=elfv1 @opindex mabi=elfv1
As Segher and I were discussing off-line, I have some problems with the current -mabi={ieee,ibm}longdouble switches as we start to planning to modify GCC 9 and GLIBC 2.27/2.28 to support __float128 as the default long double format for power server systems. My gripes are: 1) Using Warn() in rs6000.opt means that you get two warning messages when you use the switches (one from the driver, and one from cc1). 2) I feel you should not get a warning if you select the option that reflects the current default behavior (i.e. -mabi=ibmlongdouble currently for power server systems). 3) There is no way to silenece the warning (i.e. -w doesn't work on warnings in the .opt file). Both GLIBC and LIBGCC will need the ability to build support modules with an explicit long double format. 4) In the future we will need a little more flexibility in how the default is set. 5) There is a mis-match between the documentation and rs6000.opt, as these switches are documented, but use Undocumented in the rs6000.opt. These patches fix these issues. If you use -Wno-psabi, it will silence the warning. I have built these patches on a little endian power8 system, and there were no regressions. Can I check these patches into the trunk? 2017-10-21 Michael Meissner <meissner@linux.vnet.ibm.com> * config/rs6000/aix.h (TARGET_IEEEQUAD_DEFAULT): Set long double default to IBM. * config/rs6000/darwin.h (TARGET_IEEEQUAD_DEFAULT): Likewise. * config/rs6000/rs6000.opt (-mabi=ieeelongdouble): Move the warning to rs6000.c. Remove the Undocumented flag, since it has been documented. (-mabi=ibmlongdouble): Likewise. * config/rs6000/rs6000.c (TARGET_IEEEQUAD_DEFAULT): If it is not already set, set the default format for long double. (rs6000_debug_reg_global): Print whether long double is IBM or IEEE. (rs6000_option_override_internal): Rework setting long double format. Only warn if the user is changing the long double default and they did not use -Wno-psabi. * doc/invoke.texi (PowerPC options): Update the documentation for -mabi=ieeelongdouble and -mabi=ibmlongdouble.