Adding type information to instructions

Adding type information to instructions

[David Given]

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I've been having trouble finding the types of pseudos; the approach I've
been using, which is to follow the chain of pseudo's definers until I
find an instruction with enough type information to use, turns out to
fail utterly on OP_LOAD instructions; I can't find any way of getting
enough information from the opcode's arguments to determine the type of
the target.

As a result, I've had to make a minor patch to the lineariser code.
Given that the lineariser knows the information I need at the point
where it generates the instruction, it would seem to make sense to tag
the instruction with the type. This is made quite easy by the way that
the lineariser has a allocate-typed-instruction function.

Patch enclosed; it's very simple.

Does this seem like a reasonable approach? Is it something that would be
useful to have in the base builds? Are there any ramifications I should
be aware of?

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diff -rwu sparse.orig/linearize.c sparse/linearize.c
--- sparse.orig/linearize.c	2008-06-28 22:44:21.714555764 +0100
+++ sparse/linearize.c	2008-06-30 23:20:30.777932755 +0100
@@ -55,7 +55,9 @@
 
 static struct instruction *alloc_typed_instruction(int opcode, struct symbol *type)
 {
-	return alloc_instruction(opcode, type_size(type));
+	struct instruction *insn = alloc_instruction(opcode, type_size(type));
+	insn->type = type;
+	return insn;
 }
 
 static struct entrypoint *alloc_entrypoint(void)
diff -rwu sparse.orig/linearize.h sparse/linearize.h
--- sparse.orig/linearize.h	2008-06-28 22:44:21.714555764 +0100
+++ sparse/linearize.h	2008-06-30 23:20:04.425933822 +0100
@@ -71,6 +71,7 @@
 		 size:24;
 	struct basic_block *bb;
 	struct position pos;
+	struct symbol *type;
 	union {
 		pseudo_t target;
 		pseudo_t cond;		/* for branch and switch */

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Re: Adding type information to instructions

[Josh Triplett]

On Sat, 2008-07-05 at 00:43 +0100, David Given wrote:
> I've been having trouble finding the types of pseudos; the approach I've
> been using, which is to follow the chain of pseudo's definers until I
> find an instruction with enough type information to use, turns out to
> fail utterly on OP_LOAD instructions; I can't find any way of getting
> enough information from the opcode's arguments to determine the type of
> the target.
> 
> As a result, I've had to make a minor patch to the lineariser code.
> Given that the lineariser knows the information I need at the point
> where it generates the instruction, it would seem to make sense to tag
> the instruction with the type. This is made quite easy by the way that
> the lineariser has a allocate-typed-instruction function.
> 
> Patch enclosed; it's very simple.
> 
> Does this seem like a reasonable approach? Is it something that would be
> useful to have in the base builds? Are there any ramifications I should
> be aware of?

I can't think of any fundamental reason not to do this, other than the
standard reason of data structure size.  However, I'd like to hear
something from others on the list before accepting this patch.

- Josh Triplett

Re: Adding type information to instructions

[Chris Li]

On Mon, Jul 7, 2008 at 10:42 AM, Josh Triplett <josht@linux.vnet.ibm.com> wrote:
> I can't think of any fundamental reason not to do this, other than the
> standard reason of data structure size.

There is other ways to avoid the size blow up. At the linearized byte
code level,
the back end only need to know it is one of the stander C type . So we have an
array of stander ctype C type similar to ctype_declaration[].

We just need to replace the size member  with the array index in the instruction
struct..

Chris