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Added jump_rel (can't use abs jump with asm dsl). Fixes + improvements to ps1 asm meta passes.

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ed
2026-08-04 16:01:01 -04:00
parent 54a5bb9a31
commit 7289e7c89c
8 changed files with 610 additions and 208 deletions
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code/duffle/mips.h
+20 -2
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@@ -362,10 +362,28 @@ enum { _BitOffsets = 0
/* call_reg rs — jump-and-link to register-held address; link in $ra. */
#define call_reg(rs) jump_link((rs), R_RA)
/* j target — absolute jump within the current 256MB region. */
/* j target — absolute jump within the current 256MB region.
* WARNING: `jump(off)` CANNOT BE USED for within-atom jumps in the current pipeline.
* The MIPS j opcode encodes `(target_addr >> 2)` in its 26-bit immediate field; an ABSOLUTE byte address, not a relative word offset.
* The metaprogram computes `off` as a relative word offset (`target_word_idx - branch_word_idx - 1`), which the assembler/linker does NOT resolve.
*
* `jump(off)` is only safe when the BUILD PIPELINE owns the absolute position of the emitted code — i.e. when: s
* - the build emits a symbol-relative `.word` expression that the linker resolvess via `R_MIPS_26`, OR
* - the code is hand-assembled with explicit absolute targets, OR a custom post-build patcher resolves the 26-bit field.
*/
#define jump(off) enc_i(op_j, R_0, R_0, (off))
/* call_addr off — jump-and-link to immediate address. */
/* jump_rel off — unconditional relative jump (the within-atom-safe `jump`).
* MIPS I R3000A has no "branch always" opcode. The idiom for an unconditional relative jump is `beq $0, $0, off`.
*/
#define jump_rel(off) branch_equal(R_0, R_0, (off))
/* call_addr off — jump-and-link to immediate address.
*
* Same WARNING as `jump(off)` above: the jal opcode also encodes an absolute 26-bit target.
* For within-atom calls, the current pipeline has no equivalent always-taken call-and-link idiom.
* Workaround: `branch_link` (always-taken branch + explicit `la $ra, next_word_addr; jr $ra`), or just use `call_reg($tmp)` after loading the target into a register.
*/
#define call_addr(off) enc_i(op_jal, R_0, R_0, (off))
/* --- Store family (mirrors the load family) --- */