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Document new intra-section align

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Also sneak in two code style fixes forgotten in last commit
This commit is contained in:
ISSOtm
2020-04-08 15:01:36 +02:00
parent 665412c073
commit 9e3d8b22cb
2 changed files with 42 additions and 13 deletions
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49
src/asm/rgbasm.5
View File

@@ -492,13 +492,21 @@ See above for possible values for
.Ar bank ,
depending on
.Ar type .
.It Ic ALIGN Ns Bq Ar align
.It Ic ALIGN Ns Bq Ar align , offset
Place the section at an address whose
.Ar align
least‐significant bits are zero.
least‐significant bits are equal to
.Ar offset .
(Note that
.Ic ALIGN Ns Bq Ar align
is a shorthand for
.Ic ALIGN Ns Bq Ar align , No 0 ) .
This option can be used with
.Ar addr ,
.Bq Ar addr ,
as long as they don't contradict eachother.
It's also possible to request alignment in the middle of a section, see
.Sx Requesting alignment
below.
.El
.Pp
If
@@ -520,7 +528,7 @@ Section examples:
.Bl -item
.It
.Bd -literal -offset indent
SECTION "CoolStuff",ROMX
SECTION "Cool Stuff",ROMX
.Ed
This switches to the section called
.Dq CoolStuff ,
@@ -530,17 +538,17 @@ Code and data may follow.
.It
If it is needed, the the base address of the section can be specified:
.Bd -literal -offset indent
SECTION "CoolStuff",ROMX[$4567]
SECTION "Cool Stuff",ROMX[$4567]
.Ed
.It
An example with a fixed bank:
.Bd -literal -offset indent
SECTION "CoolStuff",ROMX[$4567],BANK[3]
SECTION "Cool Stuff",ROMX[$4567],BANK[3]
.Ed
.It
And if you want to force only the section's bank, and not its position within the bank, that's also possible:
.Bd -literal -offset indent
SECTION "CoolStuff",ROMX,BANK[7]
SECTION "Cool Stuff",ROMX,BANK[7]
.Ed
.It
Alignment examples:
@@ -1460,10 +1468,29 @@ provide the interface to the option stack.
will push the current set of options on the option stack.
.Ic POPO
can then later be used to restore them.
Useful if you want to change some options in an include file and you don't want
to destroy the options set by the program that included your file.
The stack's number of entries is limited only by the amount of memory in your
machine.
Useful if you want to change some options in an include file and you don't want to destroy the options set by the program that included your file.
The stack's number of entries is limited only by the amount of memory in your machine.
.Ss Requesting alignment
.Pp
While
.Ic ALIGN
as presented in
.Sx SECTIONS
is often useful as-is, sometimes you instead want a particular piece of data (or code) in the middle of the section to be aligned.
This is made easier through the use of mid-section
.Ic align Ar align , offset .
It will alter the section's attributes to ensure that the location the
.Ic align
directive is at, has its
.Ar align
lower bits equal to
.Ar offset .
.Pp
If the constraint cannot be met (for example because the section is fixed at an incompatible address), and error is produced.
Note that
.Ic align Ar align
is a shorthand for
.Ic align Ar align , No 0 .
.Sh SEE ALSO
.Xr rgbasm 1 ,
.Xr rgblink 1 ,

6
src/asm/section.c
View File

@@ -363,12 +363,14 @@ void sect_AlignPC(uint8_t alignment, uint16_t offset)
yyerror("Section's fixed address fails required alignment (PC = $%04x)",
sym_GetValue(pPCSymbol));
} else if (sect->nAlign != 0) {
if ((((sect->alignOfs + curOffset) % (1 << sect->nAlign)) - offset) % (1 << alignment)) {
if ((((sect->alignOfs + curOffset) % (1 << sect->nAlign))
- offset) % (1 << alignment)) {
yyerror("Section's alignment fails required alignment (offset from section start = $%04x)",
curOffset);
} else if (alignment > sect->nAlign) {
sect->nAlign = alignment;
sect->alignOfs = (offset - curOffset) % (1 << alignment);
sect->alignOfs =
(offset - curOffset) % (1 << alignment);
}
} else {
sect->nAlign = alignment;