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Allow 2-byte RELEXPR records to be used for branches of + or - 64KB.

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Previously, the linker gave an error if the relative displacement was more than + or - 32 KB. But 2-byte RELEXPR records are typically used for the operand of the BRL instruction, and since its address calculation wraps around within the program bank, it can effectively address + or - 64KB (i.e. any location within the program bank). Similar reasoning applies to PER, the other instruction using long relative addressing.

This would give an error in code like the following:

bigbrl  start
        brl     later
        ds      33000  ; realistic examples would have actual code here
later   rtl
        end

(This currently also gives an assembler error due to similar logic in ORCA/M, but the output file can be linked anyway.)

This issue can affect very large functions compiled with ORCA/C or ORCA/Pascal, which may sometimes have branches that go more than 32 KB forward or back.
This commit is contained in:
Stephen Heumann 2021-02-19 18:18:47 -06:00
parent 42734c7433
commit 76ba56a36b
1 changed files with 4 additions and 1 deletions
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5
pass2.asm
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@ -1385,7 +1385,7 @@ lb2 lda t1,X
blt lb2 blt lb2
lda t1-1,Y lda t1-1,Y
bpl lb6 bpl lb6
bra lb5 bra lb4a
lb3 lda #$FF lb3 lda #$FF
lb4 cmp t1,X lb4 cmp t1,X
bne lb5 bne lb5
@ -1394,6 +1394,9 @@ lb4 cmp t1,X
blt lb4 blt lb4
lda t1-1,Y lda t1-1,Y
bmi lb6 bmi lb6
lb4a lda expLength let BRL wrap around within program bank
cmp #2
bge lb6
lb5 long I,M lb5 long I,M
ph4 #0 ph4 #0
ph2 #11 ph2 #11