14 Jul
2024
14 Jul
'24
1:42 a.m.
On Sat, Jul 13, 2024 at 2:50 PM John Levine <johnl(a)taugh.com> wrote:
According to Ralph Corderoy
<ralph(a)inputplus.co.uk>:
It was a macro assembler. The macros generated assembler statements
that got assembled the normal way. I agree with the person that every
macro assembler I've ever seen did that. A semi-exception is the IBM
assembler that also had a PUNCH statement that put records into the
object file but I think that was only used to pass commands to the
linker.
This is conflating two different things over the life of the MACRO-32
language. It certainly started out as a macro assembler, but with the
introduction of the Alpha, DEC turned it into a true compiler (where
the source language happens to be VAX assembly language) that
generated native code for whatever machine it was compiled for: VAX or
Alpha; using the GEM backends.
When Compaq started the port to Itanium, they employed the same
technique; this was maintained by HP.
VSI has shifted to using LLVM as their compiler backend for the x86_64
port, with ELF as the executable file format (and presumably for
object files as well). As I understand the current state of affairs,
there is a GEM to LLVM layer that interfaces between the still-GEM
output of compiler frontends and the LLVM backend, that performs
native code generation. Macro, in particular, bypasses most of the
LLVM optimization layer.
Oh, no
wonder the translator worked so well.
Well, doesn't it depend on whether VAX MACRO kept the macros as
high-level entities when translating them, or if it processed macros in
the familiar way into instructions that sat at the same level as
hand-written ‘assembler’. I don't think this thread has made that clear
so far. The more relevant question is how they used the
macros. If the macros
were used consistently for semantically higher level things, the
translator can use the semantics of the macros when translating.
As has been mentioned, they don't do this. The output of fully
expanded MACRO-32 is basically VAX assembly language, which is then
compiled in a manner similar to how one would compile preprocessed C.
- Dan C.