e6d43a23ac
Bundles state that lives OUTSIDE the xenia-rs repo so a fresh clone on
another machine can be brought up to identical configuration via
migration/setup.sh:
- claude-memory/ ~/.claude/projects/-home-fabi-RE-Project-Sylpheed/memory/
(103 files, 1.1 MB - MEMORY.md + every
project_xenia_rs_*.md from audits
addis_signext through audit-058)
- project-root/dot-claude/ <project-root>/.claude/settings.json
(Stop hook + permissions)
- project-root/ppc-manual/ <project-root>/ppc-manual/
(PowerPC reference docs, 397 files, 3.7 MB)
- project-root/run-canary.sh <project-root>/run-canary.sh
- README.md Human-readable setup checklist
- setup.sh Idempotent installer (also reclones
xenia-canary at pinned HEAD 6de80dffe)
- MANIFEST.md Per-file mapping + per-file-not-bundled
restoration recipe
Excluded from bundle (not shippable via git):
- Sylpheed ISO (7.8 GB; copyright; manual copy required)
- sylpheed.db (395 MB; regenerable from XEX via analysis tooling)
- target/ build artifacts (rebuild on target)
- audit-runs probe firehoses (.log/.stdout/.stderr ~11 GB; rerun if needed)
- audit-runs memory dumps (.bin ~4.5 GB; rerun audit-026/027/029 if needed)
- xenia-canary checkout (setup.sh reclones from
git.mc02.dev/fabi/Xenia-Canary.git at HEAD 6de80dffe)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
262 lines
11 KiB
Markdown
262 lines
11 KiB
Markdown
# `stfs` — Store Floating-Point Single
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> **Category:** [Memory](../categories/memory.md) · **Form:** [D](../forms/D.md) · **Opcode:** `0xd0000000`
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<!-- GENERATED: BEGIN -->
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## Assembler Mnemonics
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| Mnemonic | XML entry | Flags | Description |
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| --- | --- | --- | --- |
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| `stfs` | `stfs` | — | Store Floating-Point Single |
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| `stfsu` | `stfsu` | — | Store Floating-Point Single with Update |
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| `stfsux` | `stfsux` | — | Store Floating-Point Single with Update Indexed |
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| `stfsx` | `stfsx` | — | Store Floating-Point Single Indexed |
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## Syntax
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```asm
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stfs [FS], [d]([RA0])
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stfsu [FS], [d]([RA])
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stfsux [FS], [RA], [RB]
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stfsx [FS], [RA], [RB]
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```
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## Encoding
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### `stfs` — form `D`
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- **Opcode word:** `0xd0000000`
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- **Primary opcode (bits 0–5):** `52`
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- **Extended opcode:** —
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- **Synchronising:** no
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| Bits | Field | Meaning |
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| --- | --- | --- |
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| 0–5 | `OPCD` | primary opcode |
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| 6–10 | `RT` | destination GPR (or RS when storing) |
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| 11–15 | `RA` | source GPR (0 ⇒ literal 0 for RA0 forms) |
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| 16–31 | `D/SI/UI` | 16-bit signed or unsigned immediate |
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### `stfsu` — form `D`
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- **Opcode word:** `0xd4000000`
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- **Primary opcode (bits 0–5):** `53`
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- **Extended opcode:** —
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- **Synchronising:** no
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| Bits | Field | Meaning |
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| --- | --- | --- |
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| 0–5 | `OPCD` | primary opcode |
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| 6–10 | `RT` | destination GPR (or RS when storing) |
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| 11–15 | `RA` | source GPR (0 ⇒ literal 0 for RA0 forms) |
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| 16–31 | `D/SI/UI` | 16-bit signed or unsigned immediate |
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### `stfsux` — form `X`
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- **Opcode word:** `0x7c00056e`
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- **Primary opcode (bits 0–5):** `31`
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- **Extended opcode:** `695`
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- **Synchronising:** no
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| Bits | Field | Meaning |
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| --- | --- | --- |
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| 0–5 | `OPCD` | primary opcode |
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| 6–10 | `RT/FRT/VRT` | destination |
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| 11–15 | `RA/FRA/VRA` | source A |
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| 16–20 | `RB/FRB/VRB` | source B |
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| 21–30 | `XO` | extended opcode (10 bits) |
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| 31 | `Rc` | record-form flag |
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### `stfsx` — form `X`
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- **Opcode word:** `0x7c00052e`
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- **Primary opcode (bits 0–5):** `31`
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- **Extended opcode:** `663`
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- **Synchronising:** no
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| Bits | Field | Meaning |
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| --- | --- | --- |
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| 0–5 | `OPCD` | primary opcode |
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| 6–10 | `RT/FRT/VRT` | destination |
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| 11–15 | `RA/FRA/VRA` | source A |
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| 16–20 | `RB/FRB/VRB` | source B |
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| 21–30 | `XO` | extended opcode (10 bits) |
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| 31 | `Rc` | record-form flag |
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## Operands
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| Field | Role | Description |
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| --- | --- | --- |
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| `FS` | stfs: read; stfsu: read; stfsux: read; stfsx: read | Source floating-point register. |
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| `RA0` | stfs: read; stfsx: read | Source GPR; when the encoded register number is 0 the operand is the literal 64-bit zero, **not** `r0`. |
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| `d` | stfs: read; stfsu: read | 16-bit signed displacement (`d`) added to the base address register. |
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| `RA` | stfsu: read; stfsu: write; stfsux: read; stfsux: write | Source GPR (`r0`–`r31`). |
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| `RB` | stfsux: read; stfsx: read | Source GPR. |
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## Register Effects
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### `stfs`
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- **Reads (always):** `FS`, `RA0`, `d`
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- **Reads (conditional):** _none_
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- **Writes (always):** _none_
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- **Writes (conditional):** _none_
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### `stfsu`
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- **Reads (always):** `FS`, `RA`, `d`
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- **Reads (conditional):** _none_
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- **Writes (always):** `RA`
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- **Writes (conditional):** _none_
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### `stfsux`
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- **Reads (always):** `FS`, `RA`, `RB`
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- **Reads (conditional):** _none_
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- **Writes (always):** `RA`
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- **Writes (conditional):** _none_
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### `stfsx`
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- **Reads (always):** `FS`, `RA0`, `RB`
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- **Reads (conditional):** _none_
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- **Writes (always):** _none_
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- **Writes (conditional):** _none_
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## Status-Register Effects
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_No condition-register or status-register effects._
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## Operation (pseudocode)
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```
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EA <- (RA|0) + EXTS(d)
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MEM(EA, 4) <- SingleFromDouble(FRS)
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```
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## C Translation Example
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```c
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/* C translation: the xenia-rs interpreter arm below in */
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/* Implementation References is the authoritative semantic */
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/* snapshot. Translate it line-by-line: */
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/* - ctx.gpr[N] -> r[N] (or f[]/v[] for FPRs/VRs) */
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/* - mem.read_u*/write_u* -> mem_read_u*_be / mem_write_u*_be */
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/* - ctx.update_cr_signed(fld, v) -> update_cr_signed(fld, v) */
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/* - ctx.xer_ca / xer_ov / xer_so -> xer.CA / xer.OV / xer.SO */
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/* The Register Effects and Status-Register Effects tables above */
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/* enumerate every side effect a faithful translation must emit. */
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```
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## Implementation References
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**`stfs`**
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- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="stfs"`](../../xenia-canary/tools/ppc-instructions.xml)
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- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_memory.cc:1071`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_memory.cc#L1071)
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- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:71`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L71)
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- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:375`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L375)
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- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:1437-1445`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L1437-L1445)
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<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
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```rust
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PpcOpcode::stfs => {
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let ea = if instr.ra() == 0 { 0u64 } else { ctx.gpr[instr.ra()] };
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let ea = ea.wrapping_add(instr.d() as i64 as u64) as u32;
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if let Some(t) = ctx.reservation_table.as_ref().filter(|t| t.is_enabled()) {
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if t.has_active_reservers() { t.invalidate_for_write(ea); }
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}
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mem.write_f32(ea, ctx.fpr[instr.rs()] as f32);
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ctx.pc += 4;
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}
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```
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</details>
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**`stfsu`**
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- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="stfsu"`](../../xenia-canary/tools/ppc-instructions.xml)
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- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_memory.cc:1084`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_memory.cc#L1084)
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- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:71`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L71)
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- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:376`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L376)
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- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:1446-1454`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L1446-L1454)
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<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
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```rust
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PpcOpcode::stfsu => {
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let ea = ctx.gpr[instr.ra()].wrapping_add(instr.d() as i64 as u64) as u32;
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if let Some(t) = ctx.reservation_table.as_ref().filter(|t| t.is_enabled()) {
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if t.has_active_reservers() { t.invalidate_for_write(ea); }
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}
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mem.write_f32(ea, ctx.fpr[instr.rs()] as f32);
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ctx.gpr[instr.ra()] = ea as u64;
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ctx.pc += 4;
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}
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```
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</details>
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**`stfsux`**
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- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="stfsux"`](../../xenia-canary/tools/ppc-instructions.xml)
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- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_memory.cc:1095`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_memory.cc#L1095)
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- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:71`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L71)
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- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:834`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L834)
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- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:1464-1472`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L1464-L1472)
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<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
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```rust
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PpcOpcode::stfsux => {
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let ea = ctx.gpr[instr.ra()].wrapping_add(ctx.gpr[instr.rb()]) as u32;
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if let Some(t) = ctx.reservation_table.as_ref().filter(|t| t.is_enabled()) {
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if t.has_active_reservers() { t.invalidate_for_write(ea); }
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}
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mem.write_f32(ea, ctx.fpr[instr.rs()] as f32);
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ctx.gpr[instr.ra()] = ea as u64;
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ctx.pc += 4;
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}
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```
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</details>
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**`stfsx`**
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- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="stfsx"`](../../xenia-canary/tools/ppc-instructions.xml)
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- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_memory.cc:1106`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_memory.cc#L1106)
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- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:71`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L71)
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- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:832`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L832)
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- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:1455-1463`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L1455-L1463)
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<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
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```rust
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PpcOpcode::stfsx => {
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let ea = if instr.ra() == 0 { 0u64 } else { ctx.gpr[instr.ra()] };
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let ea = ea.wrapping_add(ctx.gpr[instr.rb()]) as u32;
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if let Some(t) = ctx.reservation_table.as_ref().filter(|t| t.is_enabled()) {
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if t.has_active_reservers() { t.invalidate_for_write(ea); }
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}
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mem.write_f32(ea, ctx.fpr[instr.rs()] as f32);
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ctx.pc += 4;
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}
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```
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</details>
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<!-- GENERATED: END -->
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## Special Cases & Edge Conditions
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- **Double → single rounding.** `FRS` always holds an IEEE binary64; `stfs` rounds to binary32 using the current `FPSCR[RN]` rounding mode before writing 4 bytes. The xenia snapshot does `ctx.fpr[instr.rs()] as f32`, which Rust defines as round-to-nearest-even; this differs from PPC if `RN` is configured otherwise. Real hardware honours `RN`.
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- **FPSCR side effects.** Unlike [`lfs`](lfs.md) / [`lfd`](lfd.md) / [`stfd`](stfd.md), `stfs` **can** raise `FPSCR[XX]` (inexact), `OX` (overflow), `UX` (underflow), and `VXSNAN` (signalling NaN) per IEEE-754 narrowing rules. These take effect even though the write itself succeeds (architecturally — xenia's `as f32` cast does not surface these flags).
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- **Out-of-range doubles.** Values larger than binary32's max (~3.4e38) round to ±∞; values smaller than min normal flush to ±0 or denormal per `FPSCR[NI]`. NaNs are quieted (the signalling bit drops).
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- **`RA0` (non-update forms).** `RA = 0` in `stfs` and `stfsx` selects literal zero. Update forms `stfsu` / `stfsux` invoke `RA = 0` as an invalid form.
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- **Update-form post-write.** `stfsu` / `stfsux` write `EA` back to `RA` after the store.
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- **Big-endian write.** 4 bytes most-significant-byte first.
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- **Alignment.** Xenon tolerates unaligned 4-byte FP stores; cache-inhibited storage may raise alignment exceptions on real hardware.
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- **MSR[FP] required.** Disabled FP unit raises Floating-Point Unavailable.
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## Related Instructions
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- [`lfs`](lfs.md), [`lfsu`](lfs.md), [`lfsx`](lfs.md), [`lfsux`](lfs.md) — corresponding loads (single→double widening, can't raise exceptions).
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- [`stfd`](stfd.md) — double-precision store (no rounding, no FPSCR effects).
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- [`stfiwx`](stfiwx.md) — store-FP-as-integer-word.
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- [`stw`](stw.md) — integer word store (same width, GPR source).
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## IBM Reference
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- [AIX 7.3 — `stfs` (Store Floating-Point Single)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-stfs-store-floating-point-single-instruction)
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- [AIX 7.3 — `stfsu` / `stfsx` / `stfsux`](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-stfsu-store-floating-point-single-update-instruction)
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