Add the -mdense-math/-mno-dense-math compiler option to control emission of Dense Math Facility (DMF) instructions which may be supported on a future Power processor. The option is backed by OPTION_MASK_DMF and exposes a TARGET_DMF macro for use throughout the backend.
When -mcpu=future is specified and -mdense-math is not mentioned explicitly, DMF is enabled automatically. Explicitly requesting -mdense-math on a non-future target is a hard error. 2026-07-09 Surya Kumari Jangala <[email protected]> gcc: * config/rs6000/rs6000-cpus.def (FUTURE_MASKS_SERVER): Add OPTION_MASK_DMF. (POWERPC_MASKS): Likewise. * config/rs6000/rs6000.cc (rs6000_option_override_internal): Enable OPTION_MASK_DMF by default when TARGET_FUTURE is set and the flag was not explicitly given; emit an error and clear the flag when -mdense-math is requested on a non-future target. (rs6000_opt_masks): Add "dense-math" entry for OPTION_MASK_DMF. * config/rs6000/rs6000.opt (mdense-math): New option backed by Mask(DMF). * doc/invoke.texi: Add -mdense-math. --- gcc/config/rs6000/rs6000-cpus.def | 4 +++- gcc/config/rs6000/rs6000.cc | 14 ++++++++++++++ gcc/config/rs6000/rs6000.opt | 4 ++++ gcc/doc/invoke.texi | 12 ++++++++++-- 4 files changed, 31 insertions(+), 3 deletions(-) diff --git a/gcc/config/rs6000/rs6000-cpus.def b/gcc/config/rs6000/rs6000-cpus.def index a110860acce..365e0c6899c 100644 --- a/gcc/config/rs6000/rs6000-cpus.def +++ b/gcc/config/rs6000/rs6000-cpus.def @@ -85,7 +85,8 @@ /* -mcpu=future flags. */ #define FUTURE_MASKS_SERVER (POWER11_MASKS_SERVER \ - | OPTION_MASK_FUTURE) + | OPTION_MASK_FUTURE \ + | OPTION_MASK_DMF) /* Flags that need to be turned off if -mno-vsx. */ #define OTHER_VSX_VECTOR_MASKS (OPTION_MASK_EFFICIENT_UNALIGNED_VSX \ @@ -126,6 +127,7 @@ | OPTION_MASK_POWER10 \ | OPTION_MASK_POWER11 \ | OPTION_MASK_FUTURE \ + | OPTION_MASK_DMF \ | OPTION_MASK_P10_FUSION \ | OPTION_MASK_HTM \ | OPTION_MASK_ISEL \ diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc index d8669d9ffce..7743c9cdc4a 100644 --- a/gcc/config/rs6000/rs6000.cc +++ b/gcc/config/rs6000/rs6000.cc @@ -4381,6 +4381,19 @@ rs6000_option_override_internal (bool global_init_p) rs6000_isa_flags &= ~OPTION_MASK_MMA; } + /* Enable -mdense_math by default on future systems. */ + if (TARGET_FUTURE && (rs6000_isa_flags_explicit & OPTION_MASK_DMF) == 0) + rs6000_isa_flags |= OPTION_MASK_DMF; + + /* Turn off DMF options on non-future systems. */ + else if (!TARGET_FUTURE && TARGET_DMF) + { + if ((rs6000_isa_flags_explicit & OPTION_MASK_DMF) != 0) + error ("%qs requires %qs", "-mdense_math", "-mcpu=future"); + + rs6000_isa_flags &= ~OPTION_MASK_DMF; + } + /* Enable power10 fusion if we are tuning for power10, even if we aren't generating power10 instructions. */ if (!(rs6000_isa_flags_explicit & OPTION_MASK_P10_FUSION)) @@ -24470,6 +24483,7 @@ static struct rs6000_opt_mask const rs6000_opt_masks[] = { "power10", OPTION_MASK_POWER10, false, true }, { "power11", OPTION_MASK_POWER11, false, false }, { "future", OPTION_MASK_FUTURE, false, false }, + { "dense-math", OPTION_MASK_DMF, false, true }, { "hard-dfp", OPTION_MASK_DFP, false, true }, { "htm", OPTION_MASK_HTM, false, true }, { "isel", OPTION_MASK_ISEL, false, true }, diff --git a/gcc/config/rs6000/rs6000.opt b/gcc/config/rs6000/rs6000.opt index 2b6ec5222fc..d9e9de92b21 100644 --- a/gcc/config/rs6000/rs6000.opt +++ b/gcc/config/rs6000/rs6000.opt @@ -599,6 +599,10 @@ Target Undocumented Mask(POWER11) Var(rs6000_isa_flags) WarnRemoved mfuture Target Undocumented Mask(FUTURE) Var(rs6000_isa_flags) Warn(Do not use %<-mfuture>, use %<-mcpu=future>) +mdense-math +Target Mask(DMF) Var(rs6000_isa_flags) +Generate (do not generate) DMF (Dense Math Facility) instructions. + mprefixed Target Mask(PREFIXED) Var(rs6000_isa_flags) Generate (do not generate) prefixed memory instructions. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 606d666cd51..3e43761652e 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -1406,7 +1406,7 @@ See RS/6000 and PowerPC Options. -mgnu-attribute -mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} -mstack-protector-guard-offset=@var{offset} -mprefixed --mpcrel -mmma -mrop-protect -mprivileged +-mpcrel -mmma -mdense-math -mrop-protect -mprivileged -mno-splat-word-constant -mno-splat-float-constant -mno-ieee128-constant -mno-warn-altivec-long} @@ -31773,7 +31773,7 @@ following options: -mcrypto -mhtm -mpower8-fusion -mquad-memory -mquad-memory-atomic -mfloat128 -mfloat128-hardware -mprefixed -mpcrel -mmma --mrop-protect} +-mdense-math -mrop-protect} The particular options set for any particular CPU varies between compiler versions, depending on what setting seems to produce optimal @@ -32870,6 +32870,14 @@ Generate (do not generate) the MMA instructions. The @option{-mma} option requires that the option @option{-mcpu=power10} (or later) is enabled. +@opindex mdense-math +@opindex mno-dense-math +@item -mdense-math +@itemx -mno-dense-math +Generate (do not generate) Dense Math Facility (DMF) instructions. +The @option{-mdense-math} option requires that the option +@option{-mcpu=future} (or later) is enabled. + @opindex mrop-protect @opindex mno-rop-protect @item -mrop-protect -- 2.52.0
