[PATCH] V4, patch #8: Enable -mpcrel on Linux 64-bit, but not on other targets

[Michael Meissner <meissner at linux dot ibm dot com>]

This is the last patch in the compiler series for now.  On Linux 64-bit systems
it will enable -mpcrel (and -mprefixed-addr) by default.  On other systems, it
will not enable these switches until the tm.h for the OS enables it.

I have the 3 patches for the test suite that will be following this if things
are settling down.  At the moment, the tests have not been modified, but I will
look at your comments to see if I need to modify anything.

In addition, I will be re-vamping PCREL_OPT to take into account your comments.
That will come at a later date.

I have done a bootstrap build with all of the patches applied, and there were
no regressions in the test suite (this includes running all of the tests not
yet submitted).  After posting these patches, I will start a job to build each
set of patches in turn just to make sure there are no extra warnings.

Can I commit this patch to the trunk?

2019-09-18  Michael Meissner  <meissner@linux.ibm.com>

	* 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 275894)
+++ 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 275894)
+++ 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 275912)
+++ 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;
 
@@ -2532,6 +2542,14 @@ 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, "TARGET_PCREL_DEFAULT",
+	       TARGET_PCREL_DEFAULT);
+    }
 }
 
 
@@ -4012,26 +4030,6 @@ rs6000_option_override_internal (bool gl
       rs6000_isa_flags &= ~OPTION_MASK_FLOAT128_HW;
     }
 
-  /* -mprefixed-addr (and hence -mpcrel) requires -mcpu=future.  */
-  if (TARGET_PREFIXED_ADDR && !TARGET_FUTURE)
-    {
-      if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
-	error ("%qs requires %qs", "-mpcrel", "-mcpu=future");
-      else if ((rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED_ADDR) != 0)
-	error ("%qs requires %qs", "-mprefixed-addr", "-mcpu=future");
-
-      rs6000_isa_flags &= ~(OPTION_MASK_PCREL | OPTION_MASK_PREFIXED_ADDR);
-    }
-
-  /* -mpcrel requires prefixed load/store addressing.  */
-  if (TARGET_PCREL && !TARGET_PREFIXED_ADDR)
-    {
-      if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
-	error ("%qs requires %qs", "-mpcrel", "-mprefixed-addr");
-
-      rs6000_isa_flags &= ~OPTION_MASK_PCREL;
-    }
-
   /* Print the options after updating the defaults.  */
   if (TARGET_DEBUG_REG || TARGET_DEBUG_TARGET)
     rs6000_print_isa_options (stderr, 0, "after defaults", rs6000_isa_flags);
@@ -4163,12 +4161,89 @@ rs6000_option_override_internal (bool gl
   SUB3TARGET_OVERRIDE_OPTIONS;
 #endif
 
-  /* -mpcrel requires -mcmodel=medium, but we can't check TARGET_CMODEL until
-      after the subtarget override options are done.  */
-  if (TARGET_PCREL && TARGET_CMODEL != CMODEL_MEDIUM)
+  /* 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.
+
+     Pc-relative support also requires the medium code model.
+
+     However, we can't check for ELFv2 or -mcmodel=medium until after the
+     subtarget macros are run.
+
+     If prefixed addressing is disabled by default, and the user does -mpcrel,
+     don't force them to also specify -mprefixed-addr.  */
+  if (TARGET_FUTURE)
+    {
+      bool explicit_prefixed = ((rs6000_isa_flags_explicit
+				 & OPTION_MASK_PREFIXED_ADDR) != 0);
+      bool explicit_pcrel = ((rs6000_isa_flags_explicit
+			      & OPTION_MASK_PCREL) != 0);
+
+      /* Prefixed addressing requires 64-bit registers.  */
+      if (!TARGET_POWERPC64)
+	{
+	  if (TARGET_PCREL && explicit_pcrel)
+	    error ("%qs requires %qs", "-mpcrel", "-m64");
+
+	  else if (TARGET_PREFIXED_ADDR && explicit_prefixed)
+	    error ("%qs requires %qs", "-mprefixed-addr", "-m64");
+
+	  rs6000_isa_flags &= ~ADDRESSING_FUTURE_MASKS;
+	}
+
+      /* Only ELFv2 currently supports prefixed/pcrel addressing.  */
+      else if (rs6000_current_abi != ABI_ELFv2)
+	{
+	  if (TARGET_PCREL && explicit_pcrel)
+	    error ("%qs requires %qs", "-mpcrel", "-mabi=elfv2");
+
+	  else if (TARGET_PREFIXED_ADDR && explicit_prefixed)
+	    error ("%qs requires %qs", "-mprefixed-addr", "-mabi=elfv2");
+
+	  rs6000_isa_flags &= ~ADDRESSING_FUTURE_MASKS;
+	}
+
+      /* Pc-relative requires the medium code model.  */
+      else if (TARGET_PCREL && TARGET_CMODEL != CMODEL_MEDIUM)
+	{
+	  if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
+	    error ("%qs requires %qs", "-mpcrel", "-mcmodel=medium");
+
+	  rs6000_isa_flags &= ~OPTION_MASK_PCREL;
+	}
+
+      /* Enable defaults if desired.  */
+      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;
+	}
+    }
+
+  /* -mprefixed-addr (and hence -mpcrel) requires -mcpu=future.  */
+  if (TARGET_PREFIXED_ADDR && !TARGET_FUTURE)
     {
       if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
-	error ("%qs requires %qs", "-mpcrel", "-mcmodel=medium");
+	error ("%qs requires %qs", "-mpcrel", "-mcpu=future");
+      else if ((rs6000_isa_flags_explicit & OPTION_MASK_PREFIXED_ADDR) != 0)
+	error ("%qs requires %qs", "-mprefixed-addr", "-mcpu=future");
+
+      rs6000_isa_flags &= ~(OPTION_MASK_PCREL | OPTION_MASK_PREFIXED_ADDR);
+    }
+
+  /* -mpcrel requires prefixed load/store addressing.  */
+  if (TARGET_PCREL && !TARGET_PREFIXED_ADDR)
+    {
+      if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
+	error ("%qs requires %qs", "-mpcrel", "-mprefixed-addr");
 
       rs6000_isa_flags &= ~OPTION_MASK_PCREL;
     }

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797