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several improvements

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ceriel
1990-02-05 10:06:42 +00:00
parent 64c20956eb
commit 64e9a24564
17 changed files with 69 additions and 63 deletions
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32
doc/em/mach.nr
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@@ -22,19 +22,15 @@ two groups of 256 secondary opcodes each.
EM instructions without arguments have a single opcode assigned,
possibly escaped:
.Dr 6
|--------------|
| opcode |
|--------------|
.De
or
.Dr 6
|--------------|--------------|
| escape | opcode |
|--------------|--------------|
.De
The encoding for instructions with an argument is more complex.
Several instructions have an address from the global data area
@@ -45,37 +41,29 @@ and negative arguments.
There is always an opcode that takes the next two bytes as argument,
high byte first:
.Dr 6
|--------------|--------------|--------------|
| opcode | hibyte | lobyte |
|--------------|--------------|--------------|
.De
or
.Dr 6
|--------------|--------------|--------------|--------------|
| escape | opcode | hibyte | lobyte |
|--------------|--------------|--------------|--------------|
.De
An extra escape is provided for instructions with four or eight byte arguments.
.Dr 6
|--------------|--------------|--------------| |--------------|
| ESCAPE | opcode | hibyte |...| lobyte |
|--------------|--------------|--------------| |--------------|
|--------------|--------------|--------------| |--------------|
| ESCAPE | opcode | hibyte |...| lobyte |
|--------------|--------------|--------------| |--------------|
.De
For most instructions some argument values predominate.
The most frequent combinations of instruction and argument
will be encoded in a single byte, called a mini:
.Dr 6
|---------------|
|opcode+argument| (mini)
|---------------|
.De
The number of minis is restricted, because only
254 primary opcodes are available.
@@ -90,19 +78,15 @@ into a single opcode.
These opcodes are called shorties.
Shorties may be escaped.
.Dr 6
|--------------|--------------|
| opcode+high | lobyte | (shortie)
|--------------|--------------|
.De
or
.Dr 6
|--------------|--------------|--------------|
| escape | opcode+high | lobyte |
|--------------|--------------|--------------|
.De
Escaped shorties are useless if the normal encoding has a primary opcode.
Note that for some instruction-argument combinations
@@ -136,7 +120,7 @@ Each descriptor contains:
the number of bytes to be reserved for locals at each
invocation.
.N
This is a pointer-szied integer.
This is a pointer-sized integer.
.PT 2.
the start address of the procedure
.PE
@@ -217,6 +201,7 @@ unused
unused
.PE
.IE
.VS
.P
The program text consists of NTEXT bytes.
NTEXT is always a multiple of the wordsize.
@@ -247,12 +232,12 @@ At load time an interpreter can
perform any conversion deemed necessary, such as
reordering bytes in integers
and pointers and adding base addresses to pointers.
.BP
.A
In the following pictures we show a graphical notation of the
initializers.
The leftmost rectangle represents the leading byte.
.N 1
.VS 1 0
.DS
.PS - 4 " "
Fields marked with
@@ -271,9 +256,8 @@ contain a data or instruction pointer
contain a null terminated ASCII string
.PE 1
.DE 0
.VS 1 1
.VS
.Dr 6
-------------------
| 0 | n | repeat last initialization n times
-------------------
@@ -331,7 +315,7 @@ contain a null terminated ASCII string
-------------------------
| 8 | m | s | initialized float of size m
-------------------------
.De 3
.De
.PS - 8
.PT type~0:
If the last initialization initialized k bytes starting