This patch restructures the code so that -mvsx for example will not silently
convert the processor to power7. The user must now use -mcpu=power7 or higher.
This means if the user does -mvsx and the default processor does not have VSX
support, it will be an error.
I have built both big endian and little endian bootstrap compilers and there
were no regressions.
In addition, I constructed a test case that used every archiecture define (like
_ARCH_PWR4, etc.) and I also looked at the .machine directive generated. I ran
this test for all supported combinations of -mcpu, big/little endian, and 32/64
bit support. Every single instance generated exactly the same code with the
patches installed compared to the compiler before installing the patches.
Can I install this patch on the GCC 15 trunk?
2024-10-22 Michael Meissner <meiss...@linux.ibm.com>
gcc/
* config/rs6000/rs6000.cc (report_architecture_mismatch): New function.
Report an error if the user used an option such as -mvsx when the
default processor would not allow the option.
(rs6000_option_override_internal): Move some ISA checking code into
report_architecture_mismatch.
---
gcc/config/rs6000/rs6000.cc | 129 ++++++++++++++++++++++--------------
1 file changed, 79 insertions(+), 50 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 8388542b721..a944ffde28a 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -1173,6 +1173,7 @@ const int INSN_NOT_AVAILABLE = -1;
static void rs6000_print_isa_options (FILE *, int, const char *,
HOST_WIDE_INT, HOST_WIDE_INT);
static HOST_WIDE_INT rs6000_disable_incompatible_switches (void);
+static void report_architecture_mismatch (void);
static enum rs6000_reg_type register_to_reg_type (rtx, bool *);
static bool rs6000_secondary_reload_move (enum rs6000_reg_type,
@@ -3695,7 +3696,6 @@ rs6000_option_override_internal (bool global_init_p)
bool ret = true;
HOST_WIDE_INT set_masks;
- HOST_WIDE_INT ignore_masks;
int cpu_index = -1;
int tune_index;
struct cl_target_option *main_target_opt
@@ -3964,59 +3964,13 @@ rs6000_option_override_internal (bool global_init_p)
dwarf_offset_size = POINTER_SIZE_UNITS;
#endif
- /* Handle explicit -mno-{altivec,vsx} and turn off all of
- the options that depend on those flags. */
- ignore_masks = rs6000_disable_incompatible_switches ();
-
- /* For the newer switches (vsx, dfp, etc.) set some of the older options,
- unless the user explicitly used the -mno-<option> to disable the code. */
- if (TARGET_P9_VECTOR || TARGET_MODULO || TARGET_P9_MISC)
- rs6000_isa_flags |= (ISA_3_0_MASKS_SERVER & ~ignore_masks);
- else if (TARGET_P9_MINMAX)
- {
- if (cpu_index >= 0)
- {
- if (cpu_index == PROCESSOR_POWER9)
- {
- /* legacy behavior: allow -mcpu=power9 with certain
- capabilities explicitly disabled. */
- rs6000_isa_flags |= (ISA_3_0_MASKS_SERVER & ~ignore_masks);
- }
- else
- error ("power9 target option is incompatible with %<%s=<xxx>%> "
- "for <xxx> less than power9", "-mcpu");
- }
- else if ((ISA_3_0_MASKS_SERVER & rs6000_isa_flags_explicit)
- != (ISA_3_0_MASKS_SERVER & rs6000_isa_flags
- & rs6000_isa_flags_explicit))
- /* Enforce that none of the ISA_3_0_MASKS_SERVER flags
- were explicitly cleared. */
- error ("%qs incompatible with explicitly disabled options",
- "-mpower9-minmax");
- else
- rs6000_isa_flags |= ISA_3_0_MASKS_SERVER;
- }
- else if (TARGET_P8_VECTOR || TARGET_POWER8 || TARGET_CRYPTO)
- rs6000_isa_flags |= (ISA_2_7_MASKS_SERVER & ~ignore_masks);
- else if (TARGET_VSX)
- rs6000_isa_flags |= (ISA_2_6_MASKS_SERVER & ~ignore_masks);
- else if (TARGET_POPCNTD)
- rs6000_isa_flags |= (ISA_2_6_MASKS_EMBEDDED & ~ignore_masks);
- else if (TARGET_DFP)
- rs6000_isa_flags |= (ISA_2_5_MASKS_SERVER & ~ignore_masks);
- else if (TARGET_CMPB)
- rs6000_isa_flags |= (ISA_2_5_MASKS_EMBEDDED & ~ignore_masks);
- else if (TARGET_FPRND)
- rs6000_isa_flags |= (ISA_2_4_MASKS & ~ignore_masks);
- else if (TARGET_POPCNTB)
- rs6000_isa_flags |= (ISA_2_2_MASKS & ~ignore_masks);
- else if (TARGET_ALTIVEC)
- rs6000_isa_flags |= (OPTION_MASK_PPC_GFXOPT & ~ignore_masks);
+ /* Report trying to use things like -mmodulo to imply -mcpu=power9. */
+ report_architecture_mismatch ();
/* Disable VSX and Altivec silently if the user switched cpus to power7 in a
target attribute or pragma which automatically enables both options,
unless the altivec ABI was set. This is set by default for 64-bit, but
- not for 32-bit. Don't move this before the above code using ignore_masks,
+ not for 32-bit. Don't move this before report_architecture_mismatch
since it can reset the cleared VSX/ALTIVEC flag again. */
if (main_target_opt && !main_target_opt->x_rs6000_altivec_abi)
{
@@ -25407,6 +25361,81 @@ rs6000_disable_incompatible_switches (void)
return ignore_masks;
}
+/* In the past, we would boost up the ISA if you selected an -m<foo> option but
+ did not specify the correct -mcpu=<bar> option. I.e. if you added -mvsx,
+ GCC implictly would assume that you were building for at least power7. Now,
+ don't allow the -m<foo> option to boost up the ISA level. But you can still
+ do -mcpu=power7 -mno-vsx or -mcpu=power5 -mno-vsx. */
+
+static void
+report_architecture_mismatch (void)
+{
+ HOST_WIDE_INT ignore_masks = rs6000_disable_incompatible_switches ();
+
+ static const struct {
+ const HOST_WIDE_INT isa_flags; /* -m<foo> optiona. */
+ const HOST_WIDE_INT arch_flags; /* -mcpu=<proc> level. */
+ const char *const arch_name; /* architecture needed. */
+ } mismatches[] = {
+ {
+ OPTION_MASK_P9_VECTOR | OPTION_MASK_P9_MISC | OPTION_MASK_P9_MINMAX
+ | OPTION_MASK_MODULO,
+ ARCH_MASK_POWER9,
+ "-mcpu=power9"
+ },
+
+ {
+ OPTION_MASK_P8_VECTOR | OPTION_MASK_CRYPTO,
+ ARCH_MASK_POWER8,
+ "-mcpu=power8"
+ },
+
+ {
+ OPTION_MASK_VSX | OPTION_MASK_POPCNTD,
+ ARCH_MASK_POWER7,
+ "-mcpu=power7"
+ },
+ };
+
+ HOST_WIDE_INT isa_flags = rs6000_isa_flags;
+ HOST_WIDE_INT arch_flags = rs6000_arch_flags;
+
+ for (size_t i = 0; i < ARRAY_SIZE (mismatches); i++)
+ {
+ HOST_WIDE_INT mismatch_isa_flags = mismatches[i].isa_flags & isa_flags;
+ HOST_WIDE_INT mismatch_arch_flags = mismatches[i].arch_flags &
arch_flags;
+
+ if (mismatch_isa_flags != 0 && mismatch_arch_flags == 0)
+ {
+ for (size_t j = 0; j < ARRAY_SIZE (rs6000_opt_masks); j++)
+ {
+ HOST_WIDE_INT mask = rs6000_opt_masks[j].mask;
+
+ if ((mask & mismatch_isa_flags) != 0
+ && (mask & rs6000_isa_flags_explicit) != 0)
+ error ("%qs needs at least %qs",
+ rs6000_opt_masks[j].name,
+ mismatches[i].arch_name);
+ }
+
+ rs6000_isa_flags &= ~mismatch_isa_flags;
+ }
+ }
+
+ /* The following old options are used in multiple processors, so silently
+ enable the appropriate ISA options as previous GCC revisions did. */
+ if (TARGET_DFP)
+ rs6000_isa_flags |= (ISA_2_5_MASKS_SERVER & ~ignore_masks);
+ else if (TARGET_CMPB)
+ rs6000_isa_flags |= (ISA_2_5_MASKS_EMBEDDED & ~ignore_masks);
+ else if (TARGET_FPRND)
+ rs6000_isa_flags |= (ISA_2_4_MASKS & ~ignore_masks);
+ else if (TARGET_POPCNTB)
+ rs6000_isa_flags |= (ISA_2_2_MASKS & ~ignore_masks);
+ else if (TARGET_ALTIVEC)
+ rs6000_isa_flags |= (OPTION_MASK_PPC_GFXOPT & ~ignore_masks);
+}
+
/* Helper function for printing the function name when debugging. */
--
2.46.2
--
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meiss...@linux.ibm.com
