[PATCH] desc-cpu.scm: support passing the instruction endianness to cgen_cpu_open

Hi people!

This patch adds support for specifying the "instruction endianness" (as
oppossed to data endianness) when calling cgen_cpu_open.

This is part of a bigger work to properly support arches like BPF, where
the endianness of the instruction is different to the endianness of the
contents of the instruction's fields.

The accompanying patch for opcodes will be sent to
[email protected] today.  This CGEN patch will have to be applied
first though.

OK for master?
    
2020-05-19  Jose E. Marchesi  <[email protected]>

	* desc-cpu.scm (/gen-cpu-open): Support passing the instruction
	endianness to cgen_cpu_open.


diff --git a/desc-cpu.scm b/desc-cpu.scm
index b24c9f2..e00d8cd 100644
--- a/desc-cpu.scm
+++ b/desc-cpu.scm
@@ -788,6 +788,7 @@ static void
    CGEN_CPU_OPEN_MACHS:   bitmap of values in enum mach_attr
    CGEN_CPU_OPEN_BFDMACH: specify 1 mach using bfd name
    CGEN_CPU_OPEN_ENDIAN:  specify endian choice
+   CGEN_CPU_OPEN_INSN_ENDIAN: specify instruction endian choice
    CGEN_CPU_OPEN_END:     terminates arguments
 
    ??? Simultaneous multiple isas might not make sense, but it's not (yet)
@@ -801,6 +802,7 @@ CGEN_CPU_DESC
   CGEN_BITSET *isas = 0;  /* 0 = \"unspecified\" */
   unsigned int machs = 0; /* 0 = \"unspecified\" */
   enum cgen_endian endian = CGEN_ENDIAN_UNKNOWN;
+  enum cgen_endian insn_endian = CGEN_ENDIAN_UNKNOWN;
   va_list ap;
 
   if (! init_p)
@@ -835,6 +837,9 @@ CGEN_CPU_DESC
 	case CGEN_CPU_OPEN_ENDIAN :
 	  endian = va_arg (ap, enum cgen_endian);
 	  break;
+	case CGEN_CPU_OPEN_INSN_ENDIAN :
+	  insn_endian = va_arg (ap, enum cgen_endian);
+	  break;
 	default :
 	  opcodes_error_handler
 	    (/* xgettext:c-format */
@@ -864,11 +869,8 @@ CGEN_CPU_DESC
   cd->isas = cgen_bitset_copy (isas);
   cd->machs = machs;
   cd->endian = endian;
-  /* FIXME: for the sparc case we can determine insn-endianness statically.
-     The worry here is where both data and insn endian can be independently
-     chosen, in which case this function will need another argument.
-     Actually, will want to allow for more arguments in the future anyway.  */
-  cd->insn_endian = endian;
+  if (insn_endian == CGEN_ENDIAN_UNKNOWN)
+    cd->insn_endian = endian;
 
   /* Table (re)builder.  */
   cd->rebuild_tables = @arch@_cgen_rebuild_tables;