view docs/manual/x218.html @ 416:b4d0eafc5bfe

Fix code generation error in gcc6809 It turned out that under some circumstances, the gcc optimizer would select an instruction sequence that had the sense of a branch inverted. It seems this was due to a particular instruction pattern included in the machine description not being quite right with respect to how the condition codes were tracked. Removing that instruction pattern seems to fix things (subtraction with the arguments reversed). gcc seems to be smart enough to figure out how to reorganize code to work without this reversed sense subtraction and then do the right thing.
author William Astle <lost@l-w.ca>
date Thu, 24 Mar 2016 20:07:20 -0600
parents fc166b3bbae3
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>3.2. Dialects</A
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> LWASM supports all documented MC6809 instructions as defined by
Motorola.  By default, this does not include any MC6800 compatibility
instructions.  As of LWASM 4.11, those compatibility instructions can be
enabled using the <CODE
CLASS="PARAMETER"
>--6800compat</CODE
> option or the
<CODE
CLASS="PARAMETER"
>6800compat</CODE
> pragma.  It also supports all known HD6309
instructions.  While there is general agreement on the pneumonics for most
of the 6309 instructions, there is some variance with the block transfer
instructions.  TFM for all four variations seems to have gained the most
traction and, thus, this is the form that is recommended for LWASM. 
However, it also supports COPY, COPY-, IMP, EXP, TFRP, TFRM, TFRS, and TFRR. 
It further adds COPY+ as a synomym for COPY, IMPLODE for IMP, and EXPAND for
EXP.  </P
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>By default, LWASM accepts 6309 instructions. However, using the
<CODE
CLASS="PARAMETER"
>--6809</CODE
> parameter, you can cause it to throw errors on
6309 instructions instead.</P
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>The standard addressing mode specifiers are supported. These are the
hash sign ("#") for immediate mode, the less than sign ("&lt;") for forced
eight bit modes, and the greater than sign ("&gt;") for forced sixteen bit modes.</P
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>Additionally, LWASM supports using the asterisk ("*") to indicate
base page addressing. This should not be used in hand-written source code,
however, because it is non-standard and may or may not be present in future
versions of LWASM.</P
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