[llvm-dev] clang 4.0.0: Invalid code for builtin floating point function with -mfloat-abi=hard -ffast-math (ARM)

[Peter Jakubek via llvm-dev]

Hello,

clang/llvm 4.0.0 generates invalid calls for builtin functions with 
-mfloat-abi=hard -ffast-math.

Small example fail.c:

    // clang -O2 -target armv7a-none-none-eabi -mfloat-abi=hard 
-ffast-math -S fail.c -o -
    extern float sinf (float x);
    float sin1 (float x) {return (sinf (x));}

generates code to pass the parameter in r0 and expect the result in r0.
The same code without -ffast-math compiles correctly. It also works with 
-fno-builtin-sinf.

(-O2 is not required to trigger the bug, but makes the resulting code 
easier to read)

It seems -ffast-math changes the internal declaration of builtin 
functions, as if declared
with -mfloat-abi=soft.

Works just fine with or without -ffast-math in previous releases.

cheers,

Peter