68000: movem.w should use 2 increments (not 4) #8824
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movem exists in 2 symmetrical variants, register to memory (save to stack) and memory to register (pull from stack). Per 68000 manual, when in word mode, increment (respectively decrement) is 2, and 4 in long mode. For word mode, the various registers masks are handled by m2rfw0, r2mbw0, and r2mfw0. This patch corrects the pointer increment for r2mbw0 to 2, aligning it to m2rfw0 and r2mfw0.
ryanmkurtz
added
Feature: Processor/68000
Status: Triage
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On 68000, the movem instruction is the primary way to save registers on the stack. It comes in word (size 2) and long (size 4) flavors.
This patch corrects the modeling of the word variant of movem.
Per 68000 manual, when in word mode, increment (respectively decrement) is 2, and 4 in long mode. For word mode, the various registers masks are handled by m2rfw0, r2mbw0, and r2mfw0.
This patch corrects the pointer increment for r2mbw0 to 2 from 4, making it consistent with m2rfw0 and r2mfw0 (both correctly using 2 increments).
This corrects analysis of code blocks bookended by movem.w's. Before I would have the stack depth move from 0 to 4 then to 2; now it moves from 0 to 2 and back to 0.
(Edited 24th Dec '25 - post correction stack depth is zero as expected)