Change JMPE encoding from being relative to being absolute

Apparently NASM has been doing this in violation of the spec since
JMPE was first added. Hopefully fixing it won't cause new problems...

Signed-off-by: H. Peter Anvin (Intel) <[email protected]>

Author: H. Peter Anvin (Intel)

doc/changes.src

@@ -11,6 +11,30 @@ evolving code simpler.
 It is the production version of NASM since 2025.
 
 
+\S{cl-3.02} Version 3.02
+
+\b Fix build problems on C23 compilers using a pre-C23 version of
+   \c{<stdbool.h>} which defines \c{bool} as a macro in violation of the
+   C23 specification.
+
+\b The immediate form of the \c{JMPE} instruction (opcode \c{0F B8})
+   has been changed to an absolute address, as in
+   the Itanium Architecture Software Developer's Manual, version 2.3,
+   Volume 4, page 4:249. Hopefully this won't break whatever virtual
+   environments use \c{JMPE}, but it is the closest thing there is to
+   an official specification for this opcode.
+
+\> Being an \e{absolute} address, treat it equivalent to a \c{FAR}
+   jump and do not default to 64 bits in 64-bit mode.
+
+\> That \c{JMPE} has apparently been wrong all these years is probably
+   as good of a hint as any how much it has been actually used, but it
+   \e{does} have the possibility of breaking virtual environments. In
+   that case, please file a bug report to \W{https://bugs.nasm.us/}
+   with details about the virtual environment, and we will figure out
+   a suitable solution.
+
+
 \S{cl-3.01} Version 3.01
 
 \b A new \c{obj2} version of the \c{obj} output format, intended for

x86/insns.dat

@@ -307,10 +307,16 @@ $br $wdq  LOOPZ		near|short,cx#		[i-:	a# os e1 rel8]				8086,NOAPX
 $br $wdq  LOOPNZ	near|short,cx#		[i-:	a# os e0 rel8]				8086,NOAPX
 
 ; JMPE is obsolete, but seems to be used by a fair number of virtual environments?
-$br   JMPE	near				[i:	os 0f b8 rel]				IA64
-; 0f 00 /6 with a prefix has been repurposed in long mode
-$wdq  JMPE	rm#|near			[m:	nw o# np 0f 00 /6]			IA64,OSIZE
-$wd   JMPE	rm#|near			[m:	o#       0f 00 /6]			IA64,OSIZE,NOLONG
+; However, REP-prefixed JMPE opcodes have been repurposed.
+;
+; Per version 2.3 of the Itanium Architecture Software Developer's Manual,
+; which is the closest thing to an offical specification for JMPE,
+; the JMPE instruction is absolute and takes an operand size prefix like
+; a far JMP. As far JMPs are not promoted by default on 64 bits, follow that
+; convention.
+;
+$wdq  JMPE	imm#|near			[i:	norep o# 0f b8 i##]			IA64,OSIZE
+$wdq  JMPE	rm#|near			[m:	norep o# 0f 00 /6]			IA64,OSIZE
 
 ;# Call and return
 $br   CALL	near				[i:	os e8 rel]				8086,BND,NOAPX