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authorIan Lance Taylor <ian@airs.com>1996-06-28 16:38:05 +0000
committerIan Lance Taylor <ian@airs.com>1996-06-28 16:38:05 +0000
commit77dea5447d27240266be1b2391dcd774b90a181a (patch)
tree3642bf154a259005b46b78864dec5533be9985a2 /gas/NOTES
parenteec2f824fb7c2e409b8d2e5e72405a5ce296476f (diff)
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various trivial cleanups
Diffstat (limited to 'gas/NOTES')
-rw-r--r--gas/NOTES47
1 files changed, 6 insertions, 41 deletions
diff --git a/gas/NOTES b/gas/NOTES
index b062909..18b29b8 100644
--- a/gas/NOTES
+++ b/gas/NOTES
@@ -5,23 +5,16 @@ PORTING:
Sorry, no description of the interfaces is written up yet. Look at existing
back ends and work from there.
-New hosts: If your host system has a strange header file setup, create a
-config/ho-foo.h file for it and include the appropriate header files or
-definitions there. If your host has a broken compiler, or some broken macros
-in header files, create a host-specific file and repair the damage there.
-(See, for example, ho-rs6000.h. The "assert" macro on that system doesn't work
-right, and a flag is set to rewrite an expression in tc-m68k.c that the native
-compiler mis-compiles.)
-
-New target formats: Look at the BFD_ASSEMBLER code. The a.out code might be a
-fair example. There are no "good" examples yet, unfortunately, nor any good
-documentation of the changes.
+New hosts: The configure script, which is generated by autoconf,
+should handle all host specific configuration.
+
+New target formats: Look at the BFD_ASSEMBLER code. The a.out or ELF
+code might be a fair example. There are no "good" examples yet,
+unfortunately, nor any good documentation of the changes.
New target processors: Check first to see if the BFD_ASSEMBLER interface is
supported by the file format code you need to use.
-New environments: ???
-
DOCUMENTATION:
The internals of gas need documenting.
@@ -45,10 +38,6 @@ non-BFD_ASSEMBLER version often has multiple conditional tests inside it for
various processors or formats. As the various targets get converted over,
these will gradually go away.
-As of the moment I'm editing this file, only the "sun4" and "decstation-bsd"
-targets can really use the BFD code. Other back ends still need merging or
-touching up.
-
TO DO:
Remove DONTDEF code, commented-out code.
@@ -105,30 +94,6 @@ Torbjorn Granlund <tege@cygnus.com> writes, regarding alpha .align:
since these two instructions can dual-issue. Since .align is ued a lot by
gcc, it is an important optimization.
-Torbjorn Granlund <tege@cygnus.com> writes, regarding i386/i486/pentium:
-
- In a new publication from Intel, "Optimization for Intel's 32 bit
- Processors", they recommended code alignment on a 16 byte boundary if that
- requires less than 8 bytes of fill instructions. The Pentium is not
- affected by such alignment, the 386 wants alignment on a 4 byte boundary.
- It is the 486 that is most helped by large alignment.
-
- Recommended nop instructions:
- 1 byte: 90 xchg %eax,%eax
- 2 bytes: 8b c0 movl %eax,%eax
- 3 bytes: 8d 76 00 leal 0(%esi),%esi
- 4 bytes: 8d 74 26 00 leal 0(%esi),%esi
- 5 bytes: 8b c0 8d 76 00 movl %eax,%eax; leal 0(%esi),%esi
- 6 bytes: 8d b6 00 00 00 00 leal 0(%esi),%esi
- 7 bytes: 8d b4 26 00 00 00 00 leal 0(%esi),%esi
-
- Note that `leal 0(%esi),%esi' has a few different encodings...
-
- There are faster instructions for certain lengths, that are not true nops.
- If you can determine that a register and the condition code is dead (by
- scanning forwards for a register that is written before it is read, and
- similar for cc) you can use a `incl reg' for a 3 times faster 1 cycle nop...
-
(From old "NOTES" file to-do list, not really reviewed:)
fix relocation types for i860, perhaps by adding a ref pointer to fixS?