Re: [Qemu-devel] [PATCH 5/5] target-arm: Fix warn about implicit conversion

[Peter Maydell]

On 9 August 2016 at 20:02, Pranith Kumar <address@hidden> wrote:
> Clang warns about an implicit conversion as follows:
>
> /mnt/devops/code/qemu/target-arm/neon_helper.c:1075:1: warning: implicit 
> conversion from 'int' to 'int8_t' (aka 'signed char') changes value from 128 
> to -128 [-Wconstant-conversion]
> NEON_VOP_ENV(qrshl_s8, neon_s8, 4)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /mnt/devops/code/qemu/target-arm/neon_helper.c:116:83: note: expanded from 
> macro 'NEON_VOP_ENV'
> uint32_t HELPER(glue(neon_,name))(CPUARMState *env, uint32_t arg1, uint32_t 
> arg2) \
>                                                                               
>     ^
> /mnt/devops/code/qemu/target-arm/neon_helper.c:106:5: note: expanded from 
> macro '\
> NEON_VOP_BODY'
>     NEON_DO##n; \
>     ^~~~~~~~~~
> <scratch space>:21:1: note: expanded from here
> NEON_DO4
> ^~~~~~~~
> /mnt/devops/code/qemu/target-arm/neon_helper.c:93:5: note: expanded from 
> macro 'NEON_DO4'
>     NEON_FN(vdest.v1, vsrc1.v1, vsrc2.v1); \
>     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /mnt/devops/code/qemu/target-arm/neon_helper.c:1054:23: note: expanded from 
> macro 'NEON_FN'
>             dest = (1 << (sizeof(src1) * 8 - 1)); \
>                  ~  ~~^~~~~~~~~~~~~~~~~~~~~~~~~
>
> Fix it by casting to appropriate type.
>
> Signed-off-by: Pranith Kumar <address@hidden>
> ---
>  target-arm/neon_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target-arm/neon_helper.c b/target-arm/neon_helper.c
> index 1f1844f..ebdf7c9 100644
> --- a/target-arm/neon_helper.c
> +++ b/target-arm/neon_helper.c
> @@ -1051,7 +1051,7 @@ uint64_t HELPER(neon_qrshl_u64)(CPUARMState *env, 
> uint64_t val, uint64_t shiftop
>      if (tmp >= (ssize_t)sizeof(src1) * 8) { \
>          if (src1) { \
>              SET_QC(); \
> -            dest = (1 << (sizeof(src1) * 8 - 1)); \
> +            dest = (typeof(dest))(1 << (sizeof(src1) * 8 - 1)); \
>              if (src1 > 0) { \
>                  dest--; \
>              } \

A bit ugly but I guess it works. (The code is
deliberately setting dest to "most negative integer
that fits into src1 type".)

Reviewed-by: Peter Maydell <address@hidden>

thanks
-- PMM