aix.h (OS_MISSING_POWERPC64): Define.

	* config/rs6000/aix.h (OS_MISSING_POWERPC64): Define.
	(OS_MISSING_ALTIVEC): Define.
	* config/rs6000/darwin.h (ASM_SPEC): Be generous about supplying
	-force_cpusubtype_ALL.
	* config/rs6000/rs6000.c (rs6000_override_options): Rearrange
	CPU information table; now always set all CPU-specific values.
	Also, use Altivec and powerpc64 when chip and OS supports them.

From-SVN: r74820

gcc/ChangeLog

 2003-12-18  Geoffrey Keating  <geoffk@apple.com>
 
+	* config/rs6000/aix.h (OS_MISSING_POWERPC64): Define.
+	(OS_MISSING_ALTIVEC): Define.
+	* config/rs6000/darwin.h (ASM_SPEC): Be generous about supplying
+	-force_cpusubtype_ALL.
+	* config/rs6000/rs6000.c (rs6000_override_options): Rearrange
+	CPU information table; now always set all CPU-specific values.
+	Also, use Altivec and powerpc64 when chip and OS supports them.
+
+2003-12-18  Geoffrey Keating  <geoffk@apple.com>
+
 	* fixinc/inclhack.def (darwin_macho_dyldh): New.
 	* fixinc/fixincl.x: Regenerate.
 

gcc/config/rs6000/aix.h

@@ -241,3 +241,8 @@
 
 /* Print subsidiary information on the compiler version in use.  */
 #define TARGET_VERSION ;
+
+/* No version of AIX fully supports AltiVec or 64-bit instructions in
+   32-bit mode.  */
+#define OS_MISSING_POWERPC64 1
+#define OS_MISSING_ALTIVEC 1

gcc/config/rs6000/darwin.h

@@ -98,9 +98,14 @@ do {									\
 %{static: %{Zdynamic: %e conflicting code gen style switches are used}}\
 %{!static:%{!mdynamic-no-pic:-fPIC}}"
 
+/* It's virtually impossible to predict all the possible combinations
+   of -mcpu and -maltivec and whatnot, so just supply
+   -force_cpusubtype_ALL if any are seen.  Radar 3492132 against the
+   assembler is asking for a .machine directive so we could get this
+   really right.  */
 #define ASM_SPEC "-arch ppc \
   %{Zforce_cpusubtype_ALL:-force_cpusubtype_ALL} \
-  %{!Zforce_cpusubtype_ALL:%{maltivec:-force_cpusubtype_ALL}}"
+  %{!Zforce_cpusubtype_ALL:%{maltivec|mcpu=*|mpowerpc64:-force_cpusubtype_ALL}}"
 
 #undef SUBTARGET_EXTRA_SPECS
 #define SUBTARGET_EXTRA_SPECS			\

gcc/config/rs6000/rs6000.c

@@ -624,147 +624,79 @@ rs6000_override_options (const char *default_cpu)
 {
   size_t i, j;
   struct rs6000_cpu_select *ptr;
+  int set_masks;
 
-  /* Simplify the entries below by making a mask for any POWER
-     variant and any PowerPC variant.  */
+  /* Simplifications for entries below.  */
 
-#define POWER_MASKS (MASK_POWER | MASK_POWER2 | MASK_MULTIPLE | MASK_STRING)
-#define POWERPC_MASKS (MASK_POWERPC | MASK_PPC_GPOPT \
-		       | MASK_PPC_GFXOPT | MASK_POWERPC64)
-#define POWERPC_OPT_MASKS (MASK_PPC_GPOPT | MASK_PPC_GFXOPT)
+  enum {
+    POWERPC_BASE_MASK = MASK_POWERPC | MASK_NEW_MNEMONICS,
+    POWERPC_7400_MASK = POWERPC_BASE_MASK | MASK_PPC_GFXOPT | MASK_ALTIVEC
+  };
 
+  /* This table occasionally claims that a processor does not support
+     a particular feature even though it does, but the feature is slower
+     than the alternative.  Thus, it shouldn't be relied on as a
+     complete description of the processor's support.  
+
+     Please keep this list in order, and don't forget to update the
+     documentation in invoke.texi when adding a new processor or
+     flag.  */
   static struct ptt
     {
       const char *const name;		/* Canonical processor name.  */
       const enum processor_type processor; /* Processor type enum value.  */
       const int target_enable;	/* Target flags to enable.  */
-      const int target_disable;	/* Target flags to disable.  */
     } const processor_target_table[]
-      = {{"common", PROCESSOR_COMMON, MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_MASKS},
-	 {"power", PROCESSOR_POWER,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"power2", PROCESSOR_POWER,
-	    MASK_POWER | MASK_POWER2 | MASK_MULTIPLE | MASK_STRING,
-	    POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"power3", PROCESSOR_PPC630,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS},
-	 {"power4", PROCESSOR_POWER4,
-            MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS | MASK_MFCRF,
-            POWER_MASKS},
-	 {"powerpc", PROCESSOR_POWERPC,
-	    MASK_POWERPC | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"powerpc64", PROCESSOR_POWERPC64,
-	    MASK_POWERPC | MASK_POWERPC64 | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS},
-	 {"rios", PROCESSOR_RIOS1,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"rios1", PROCESSOR_RIOS1,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"rsc", PROCESSOR_PPC601,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"rsc1", PROCESSOR_PPC601,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"rios2", PROCESSOR_RIOS2,
-	    MASK_POWER | MASK_MULTIPLE | MASK_STRING | MASK_POWER2,
-	    POWERPC_MASKS | MASK_NEW_MNEMONICS},
-	 {"rs64a", PROCESSOR_RS64A,
-	    MASK_POWERPC | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS},
-	 {"401", PROCESSOR_PPC403,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
+      = {{"401", PROCESSOR_PPC403, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
 	 {"403", PROCESSOR_PPC403,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS | MASK_STRICT_ALIGN,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"405", PROCESSOR_PPC405,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"405fp", PROCESSOR_PPC405,
-	    MASK_POWERPC | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"440", PROCESSOR_PPC440,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"440fp", PROCESSOR_PPC440,
-	    MASK_POWERPC | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"505", PROCESSOR_MPCCORE,
-	    MASK_POWERPC | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
+	  POWERPC_BASE_MASK | MASK_SOFT_FLOAT | MASK_STRICT_ALIGN},
+	 {"405", PROCESSOR_PPC405, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"405fp", PROCESSOR_PPC405, POWERPC_BASE_MASK},
+	 {"440", PROCESSOR_PPC440, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"440fp", PROCESSOR_PPC440, POWERPC_BASE_MASK},
+	 {"505", PROCESSOR_MPCCORE, POWERPC_BASE_MASK},
 	 {"601", PROCESSOR_PPC601,
-	    MASK_POWER | MASK_POWERPC | MASK_NEW_MNEMONICS | MASK_MULTIPLE | MASK_STRING,
-	    MASK_POWER2 | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"602", PROCESSOR_PPC603,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"603", PROCESSOR_PPC603,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"603e", PROCESSOR_PPC603,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"ec603e", PROCESSOR_PPC603,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"604", PROCESSOR_PPC604,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"604e", PROCESSOR_PPC604e,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"620", PROCESSOR_PPC620,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS},
-	 {"630", PROCESSOR_PPC630,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS},
-	 {"740", PROCESSOR_PPC750,
- 	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
- 	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"750", PROCESSOR_PPC750,
- 	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
- 	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"G3", PROCESSOR_PPC750,
- 	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
- 	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"7400", PROCESSOR_PPC7400,
-            MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-            POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"7450", PROCESSOR_PPC7450,
-            MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-            POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"G4", PROCESSOR_PPC7450,
-            MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-            POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"8540", PROCESSOR_PPC8540,
-	    MASK_POWERPC | MASK_PPC_GFXOPT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | MASK_PPC_GPOPT | MASK_POWERPC64},
-	 {"801", PROCESSOR_MPCCORE,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"821", PROCESSOR_MPCCORE,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"823", PROCESSOR_MPCCORE,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
-	 {"860", PROCESSOR_MPCCORE,
-	    MASK_POWERPC | MASK_SOFT_FLOAT | MASK_NEW_MNEMONICS,
-	    POWER_MASKS | POWERPC_OPT_MASKS | MASK_POWERPC64},
+	  MASK_POWER | POWERPC_BASE_MASK | MASK_MULTIPLE | MASK_STRING},
+	 {"602", PROCESSOR_PPC603, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"603", PROCESSOR_PPC603, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"603e", PROCESSOR_PPC603, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"604", PROCESSOR_PPC604, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"604e", PROCESSOR_PPC604e, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"620", PROCESSOR_PPC620, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"630", PROCESSOR_PPC630, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"740", PROCESSOR_PPC750, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"7400", PROCESSOR_PPC7400, POWERPC_7400_MASK},
+	 {"7450", PROCESSOR_PPC7450, POWERPC_7400_MASK},
+	 {"750", PROCESSOR_PPC750, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"801", PROCESSOR_MPCCORE, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"821", PROCESSOR_MPCCORE, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"823", PROCESSOR_MPCCORE, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"8540", PROCESSOR_PPC8540, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"860", PROCESSOR_MPCCORE, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
 	 {"970", PROCESSOR_POWER4,
-	    MASK_POWERPC | POWERPC_OPT_MASKS | MASK_NEW_MNEMONICS | MASK_MFCRF,
-	    POWER_MASKS},
+	  POWERPC_7400_MASK | MASK_PPC_GPOPT | MASK_MFCRF | MASK_POWERPC64},
+	 {"common", PROCESSOR_COMMON, MASK_NEW_MNEMONICS},
+	 {"ec603e", PROCESSOR_PPC603, POWERPC_BASE_MASK | MASK_SOFT_FLOAT},
+	 {"G3", PROCESSOR_PPC750, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"G4",  PROCESSOR_PPC7450, POWERPC_7400_MASK},
 	 {"G5", PROCESSOR_POWER4,
-	    MASK_POWERPC | POWERPC_OPT_MASKS | MASK_NEW_MNEMONICS | MASK_MFCRF,
-	    POWER_MASKS}};
+	  POWERPC_7400_MASK | MASK_PPC_GPOPT | MASK_MFCRF | MASK_POWERPC64},
+	 {"power", PROCESSOR_POWER, MASK_POWER | MASK_MULTIPLE | MASK_STRING},
+	 {"power2", PROCESSOR_POWER,
+	  MASK_POWER | MASK_POWER2 | MASK_MULTIPLE | MASK_STRING},
+	 {"power3", PROCESSOR_PPC630, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"power4", PROCESSOR_POWER4, POWERPC_BASE_MASK | MASK_PPC_GFXOPT},
+	 {"powerpc", PROCESSOR_POWERPC, POWERPC_BASE_MASK},
+	 {"powerpc64", PROCESSOR_POWERPC64,
+	  POWERPC_BASE_MASK | MASK_POWERPC64},
+	 {"rios", PROCESSOR_RIOS1, MASK_POWER | MASK_MULTIPLE | MASK_STRING},
+	 {"rios1", PROCESSOR_RIOS1, MASK_POWER | MASK_MULTIPLE | MASK_STRING},
+	 {"rios2", PROCESSOR_RIOS2,
+	  MASK_POWER | MASK_POWER2 | MASK_MULTIPLE | MASK_STRING},
+	 {"rsc", PROCESSOR_PPC601, MASK_POWER | MASK_MULTIPLE | MASK_STRING},
+	 {"rsc1", PROCESSOR_PPC601, MASK_POWER | MASK_MULTIPLE | MASK_STRING},
+	 {"rs64a", PROCESSOR_RS64A, POWERPC_BASE_MASK},
+      };
 
   const size_t ptt_size = ARRAY_SIZE (processor_target_table);
 
@@ -773,6 +705,28 @@ rs6000_override_options (const char *default_cpu)
   /* Save current -mstring/-mno-string status.  */
   int string = TARGET_STRING;
 
+  /* Some OSs don't support saving the high part of 64-bit registers on
+     context switch.  Other OSs don't support saving Altivec registers.
+     On those OSs, we don't touch the MASK_POWERPC64 or MASK_ALTIVEC
+     settings; if the user wants either, the user must explicitly specify
+     them and we won't interfere with the user's specification.  */
+
+  enum {
+    POWER_MASKS = MASK_POWER | MASK_POWER2 | MASK_MULTIPLE | MASK_STRING,
+    POWERPC_MASKS = (POWERPC_BASE_MASK | MASK_PPC_GPOPT 
+		     | MASK_PPC_GFXOPT | MASK_POWERPC64 | MASK_ALTIVEC
+		     | MASK_MFCRF)
+  };
+ set_masks = POWER_MASKS | POWERPC_MASKS | MASK_SOFT_FLOAT;
+#ifdef OS_MISSING_POWERPC64
+  if (OS_MISSING_POWERPC64)
+    set_masks &= ~MASK_POWERPC64;
+#endif
+#ifdef OS_MISSING_ALTIVEC
+  if (OS_MISSING_ALTIVEC)
+    set_masks &= ~MASK_ALTIVEC;
+#endif
+
   /* Identify the processor type.  */
   rs6000_select[0].string = default_cpu;
   rs6000_cpu = TARGET_POWERPC64 ? PROCESSOR_DEFAULT64 : PROCESSOR_DEFAULT;
@@ -790,8 +744,9 @@ rs6000_override_options (const char *default_cpu)
 
 		if (ptr->set_arch_p)
 		  {
-		    target_flags |= processor_target_table[j].target_enable;
-		    target_flags &= ~processor_target_table[j].target_disable;
+		    target_flags &= ~set_masks;
+		    target_flags |= (processor_target_table[j].target_enable
+				     & set_masks);
 		  }
 		break;
 	      }

gcc/doc/invoke.texi

@@ -7239,13 +7239,15 @@ should normally not specify either @option{-mnew-mnemonics} or
 @opindex mcpu
 Set architecture type, register usage, choice of mnemonics, and
 instruction scheduling parameters for machine type @var{cpu_type}.
-Supported values for @var{cpu_type} are @samp{rios}, @samp{rios1},
-@samp{rsc}, @samp{rios2}, @samp{rs64a}, @samp{601}, @samp{602},
-@samp{603}, @samp{603e}, @samp{604}, @samp{604e}, @samp{620},
-@samp{630}, @samp{740}, @samp{7400}, @samp{7450}, @samp{G4}, 
-@samp{750}, @samp{G3},  @samp{power}, @samp{power2}, @samp{powerpc}, 
-@samp{403}, @samp{505}, @samp{801}, @samp{821}, @samp{823}, @samp{860},
-@samp{970}, @samp{G5} and @samp{common}.
+Supported values for @var{cpu_type} are @samp{401}, @samp{403},
+@samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{505},
+@samp{601}, @samp{602}, @samp{603}, @samp{603e}, @samp{604},
+@samp{604e}, @samp{620}, @samp{630}, @samp{740}, @samp{7400},
+@samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
+@samp{860}, @samp{970}, @samp{common}, @samp{ec603e}, @samp{G3},
+@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3},
+@samp{power4}, @samp{powerpc}, @samp{powerpc64}, @samp{rios},
+@samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64a}.
 
 @option{-mcpu=common} selects a completely generic processor.  Code
 generated under this option will run on any POWER or PowerPC processor.
@@ -7263,47 +7265,23 @@ The other options specify a specific processor.  Code generated under
 those options will run best on that processor, and may not run at all on
 others.
 
-The @option{-mcpu} options automatically enable or disable other
-@option{-m} options as follows:
-
-@table @samp
-@item common
-@option{-mno-power}, @option{-mno-powerpc}
-
-@item power
-@itemx power2
-@itemx rios1
-@itemx rios2
-@itemx rsc
-@option{-mpower}, @option{-mno-powerpc}, @option{-mno-new-mnemonics}
-
-@item powerpc
-@itemx rs64a
-@itemx 602
-@itemx 603
-@itemx 603e
-@itemx 604
-@itemx 620
-@itemx 630
-@itemx 740
-@itemx 7400
-@itemx 7450
-@itemx G4
-@itemx 750
-@itemx G3
-@itemx 505
-@itemx 970
-@itemx G5
-@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}
-
-@item 601
-@option{-mpower}, @option{-mpowerpc}, @option{-mnew-mnemonics}
-
-@item 403
-@itemx 821
-@itemx 860
-@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}, @option{-msoft-float}
-@end table
+The @option{-mcpu} options automatically enable or disable the
+following options: @option{-maltivec}, @option{-mhard-float},
+@option{-mmfcrf}, @option{-mmultiple}, @option{-mnew-mnemonics},
+@option{-mpower}, @option{-mpower2}, @option{-mpowerpc64},
+@option{-mpowerpc-gpopt}, @option{-mpowerpc-gfxopt},
+@option{-mstring}.  The particular options set for any particular CPU
+will vary between compiler versions, depending on what setting seems
+to produce optimal code for that CPU; it doesn't necessarily reflect
+the actual hardware's capabilities.  If you wish to set an individual
+option to a particular value, you may specify it after the
+@option{-mcpu} option, like @samp{-mcpu=970 -mno-altivec}.
+
+On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are
+not enabled or disabled by the @option{-mcpu} option at present, since
+AIX does not have full support for these options.  You may still
+enable or disable them individually if you're sure it'll work in your
+environment.
 
 @item -mtune=@var{cpu_type}
 @opindex mtune