uditjainstjis opened a new pull request, #19513:
URL: https://github.com/apache/nuttx/pull/19513
## Summary
`libs/libbuiltin/compiler-rt` globs **every** `arm/*.S` source into the
builtins
library (`$(wildcard .../arm/*.S)` in `Make.defs`, `file(GLOB ...)` in
`CMakeLists.txt`). Several of those hand-written VFP assembly files require
FPU
features the selected target may not have. Upstream compiler-rt selects them
conditionally in its own CMake logic; NuttX did not, so enabling
`BUILTIN_COMPILER_RT` on a single-precision-FPU Arm target (e.g. Cortex-M33
with
`-mfpu=fpv5-sp-d16`, as on the Raspberry Pi Pico 2 / RP2350) breaks the build
with assembler errors such as:
```
compiler-rt/lib/builtins/arm/adddf3vfp.S:24: Error: selected FPU does not
support instruction -- `vadd.f64 d6,d6,d7'
compiler-rt/lib/builtins/arm/chkstk.S:29: Error: instruction not supported
in Thumb16 mode -- `subs r5,r5,#4096'
```
This filters the Arm `.S` source list to match the configured FPU, in both
the
Makefile and CMake builds:
- `chkstk.S` / `chkstk2.S` are Windows/MinGW-only stack probes — always
dropped;
- with no hardware FPU (`!CONFIG_ARCH_FPU`), every `arm/*vfp.S` is dropped;
- with a single-precision FPU (`!CONFIG_ARCH_DPFPU`), the double-precision
`*df*vfp.S` routines are dropped.
The excluded set mirrors upstream compiler-rt's own conditional selection.
Fixes #17386.
## Impact
- Fixes the build for `CONFIG_BUILTIN_COMPILER_RT=y` on single-precision-FPU
and
soft-float Arm targets (previously failed to link/assemble).
- No behavioural change for targets with a double-precision FPU or for
non-Arm architectures: those targets keep the same source set (the double-
precision `*df*vfp.S` files are only removed when `CONFIG_ARCH_DPFPU` is
unset,
and the whole block is guarded by `CONFIG_ARCH_ARM`).
- Build system only; no runtime code, API, or documentation changes.
## Testing
Host: Ubuntu 24.04 (x86_64), `arm-none-eabi-gcc` 14.2.rel1 (matching the
toolchain in the original report), compiler-rt 17.0.1 (NuttX default
`LIB_COMPILER_RT_VERSION`).
Reproduced the failure by assembling every `arm/*.S` builtin with the
Cortex-M33
single-precision flags from the issue
(`-march=armv8-m.main+dsp -mtune=cortex-m33 -mfpu=fpv5-sp-d16
-mfloat-abi=softfp -mthumb -mcmse`):
```
[RESULT] total=86 FAIL=18 PASS=68
FAILING: adddf3vfp.S chkstk.S divdf3vfp.S eqdf2vfp.S extendsfdf2vfp.S
fixdfsivfp.S fixunsdfsivfp.S floatsidfvfp.S floatunssidfvfp.S
gedf2vfp.S gtdf2vfp.S ledf2vfp.S ltdf2vfp.S muldf3vfp.S nedf2vfp.S
subdf3vfp.S truncdfsf2vfp.S unorddf2vfp.S
```
Applying this patch's exclusion set (17 double-precision `*df*vfp.S` files +
`chkstk.S`) and re-assembling the remainder:
```
[POST-FIX] assembled=68 remaining_failures=0
```
`negdf2vfp.S` and the single-precision `*sf*vfp.S` routines are correctly
retained (they assemble under a single-precision FPU). Verified the Make
filter
logic independently: for a single-precision target it removes exactly the
DP-VFP
and `chkstk` files while keeping `negdf2vfp.S`, `addsf3vfp.S`, and `.c`
sources.
`./tools/checkpatch.sh -f` passes on both changed files (including
`cmake-format`).
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