[uurl]

What This PR Does

Implements #1224 across the 9-commit libdevice_math series (#1638, #1645, #1646, #1649, #1650, #1651, #1652, #1653, #1660), replacing hand-maintained math dispatch tables across three crates with a single generated table backed by libdevice.10.bc evidence and expanding libm 0.2.16 coverage from 72 to 120 of 124 f32/f64 exports:

1. Add intrinsics/overlay/libdevice_math.toml + libdevice.10.bc signature verification and generate dialect-mir math dispatch (cuda-intrinsics-gen, dialect-mir, mir-importer, rustc-codegen-cuda)
2. Extract float-math lowering into mir-lower/src/convert/ops/float_math.rs driven by generated RustFloatMathLowering (mir-lower)
3. Lower scalar aliases (tgamma, ilogb, ldexp, erf, j0, y0, ...), entry-block out-parameter adapters (frexp, modf, remquo), lgamma_r, C23 fmaximum/fminimum, and j1 (mir-lower, examples/math_special)

---

1. Generated libm -> libdevice Dispatch (#1224)

Previously, wiring a single libm or std::sys::cmath function required hand-editing ~10 sites across rustc-codegen-cuda/src/collector.rs, mir-importer, dialect-mir, and mir-lower:

BEFORE (hand-maintained across 4 crates):
  collector.rs       ──► hardcoded `std::sys::cmath::*` match list
  mir-importer       ──► hand-written `RustFloatMathIntrinsic` enum + `from_core_path` / `from_libm_path`
  dialect-mir        ──► hand-written `CALLEE_*` constants + `is_libdevice_backed_placeholder`
  mir-lower          ──► hand-written placeholder -> `__nv_*` match table

AFTER (`intrinsics/overlay/libdevice_math.toml` -> `cuda-intrinsics-gen`):
  libdevice_math.toml + cuda-13.0.json (102 signatures verified against libdevice.10.bc)
    │
    ▼
  crates/dialect-mir/src/generated/libdevice_math.rs
    ├──► collector.rs   `is_intrinsic_lowered_cmath_shim(fn_path)`
    ├──► mir-importer   `from_core_path` + `from_libm_path` -> `CALLEE_*`
    ├──► codegen        `link_requirement()` -> `MathLink::{Always, Libnvvm, Never}`
    └──► mir-lower      `RustFloatMathIntrinsic::lowering(self) -> RustFloatMathLowering`

---

2. Entry-Block Out-Parameter Adapters & IEEE Edge-Case Lowerings (mir-lower)

Function Family                Lowering in `mir-lower/src/convert/ops/float_math.rs`
─────────────────────────────  ──────────────────────────────────────────────────────────────────────────
`frexp`, `modf`, `remquo`      Hoists `llvm.alloca` to function entry block (`0` `.local` traffic after
                               `opt -O2` SROA); normalizes `frexp(+-inf/NaN) -> (x, 0)` and `remquo` NaN -> `quo = 0`
`lgamma_r`, `lgammaf_r`        Composes `__nv_lgamma`, `__nv_floor`, and `__nv_fmod(floor(x), 2.0)` with
                               `-0.0 -> (+inf, -1)`, negative integer poles `-> (+inf, +1)`, `-inf -> (+inf, +1)`
C23 `fmaximum*` / `fminimum*`  Pure LLVM `fcmp` (empty fast-math flags) + sign-bit tie-break (`-0.0 < +0.0`)
`j1`, `j1f`                    Calls `__nv_j1{,f}` and normalizes `|x| == inf -> +0.0`

---

Verification

• RTX 5090 (sm_120a) GPU Execution & Sanitizer:
  • cargo oxide run math_special: 2,822 / 2,822 f32 and f64 checks PASS (compute-sanitizer --tool memcheck: 0 errors, 0 .local instructions emitted for frexp, modf, remquo, lgamma_r, and C23 minmax).
  • cargo oxide run libm_math & cargo oxide run libdevice_math: PASS.
• Generator & Bitcode Verification:
  • cargo run -p cuda-intrinsics-gen -- check & verify-libdevice: PASS (102 libdevice.10.bc signatures verified).
• Tests, Lints & Guards:
  • cargo test -p cuda-intrinsics-gen -p dialect-mir -p mir-importer -p mir-lower -p cuda-oxide-codegen --all-targets: 3,494 tests PASS
  • just fmt-check, just clippy, scripts/sync-example-locks.sh --check, and all 18 scripts/check-*.sh guards: all PASS

Closes #1224

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[nihalpasham]

Thanks, this is a very clean implementation of #1224 across the generator, libdevice.10.bc signature verification, entry-block out-parameter adapters, and IEEE edge-case normalizations. Since #1660 carries all 9 commits of the #1638..#1660 stack in linear order, I am landing the full stack through #1660 with one polish commit on top (8d77b1c94):

• Generated RustFloatMathLowering in dialect-mir from the lowering column in libdevice_math.toml and extracted float-math lowering out of call.rs into mir-lower/src/convert/ops/float_math.rs.
• Removed the redundant intrinsics/generated/libdevice_math.rs staging copy, padded the intrinsics/libdevice-math.md table, and added /// doc comments across internal helpers and types.
• Consolidated the 6 new example workspaces into examples/math_special (keeping all 2,822 f32/f64 GPU checks) so CI does not pay 5 extra workspace builds.

At 8d77b1c94, math_special (2,822 checks on RTX 5090 sm_120a, compute-sanitizer clean), verify-libdevice, all compiler suites, and all 18 guard checks pass. Merging once CI is green.

[nihalpasham]

/ok to test 8d77b1c

[nihalpasham]

/ok to test e4d3319