Re: [Qemu-devel] [PATCH 01/12] target-i386: Avoid shifting left into sign bit

[Michael S. Tsirkin]

On Mon, Mar 10, 2014 at 07:10:37PM +0000, Peter Maydell wrote:
> Add 'U' suffixes where necessary to avoid (1 << 31) which
> shifts left into the sign bit, which is undefined behaviour.
> 
> Signed-off-by: Peter Maydell <address@hidden>

While not required for correctness,
I think it would be cleaner to change them all to 1U, for consistency.


> ---
>  target-i386/cpu.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index 0014acc..064f987 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -202,7 +202,7 @@
>  #define CR0_NE_MASK  (1 << 5)
>  #define CR0_WP_MASK  (1 << 16)
>  #define CR0_AM_MASK  (1 << 18)
> -#define CR0_PG_MASK  (1 << 31)
> +#define CR0_PG_MASK  (1U << 31)
>  
>  #define CR4_VME_MASK  (1 << 0)
>  #define CR4_PVI_MASK  (1 << 1)
> @@ -436,7 +436,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_HT (1 << 28)
>  #define CPUID_TM (1 << 29)
>  #define CPUID_IA64 (1 << 30)
> -#define CPUID_PBE (1 << 31)
> +#define CPUID_PBE (1U << 31)
>  
>  #define CPUID_EXT_SSE3     (1 << 0)
>  #define CPUID_EXT_PCLMULQDQ (1 << 1)
> @@ -467,7 +467,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_EXT_AVX      (1 << 28)
>  #define CPUID_EXT_F16C     (1 << 29)
>  #define CPUID_EXT_RDRAND   (1 << 30)
> -#define CPUID_EXT_HYPERVISOR  (1 << 31)
> +#define CPUID_EXT_HYPERVISOR  (1U << 31)
>  
>  #define CPUID_EXT2_FPU     (1 << 0)
>  #define CPUID_EXT2_VME     (1 << 1)
> @@ -496,7 +496,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_EXT2_RDTSCP  (1 << 27)
>  #define CPUID_EXT2_LM      (1 << 29)
>  #define CPUID_EXT2_3DNOWEXT (1 << 30)
> -#define CPUID_EXT2_3DNOW   (1 << 31)
> +#define CPUID_EXT2_3DNOW   (1U << 31)
>  
>  /* CPUID[8000_0001].EDX bits that are aliase of CPUID[1].EDX bits on AMD 
> CPUs */
>  #define CPUID_EXT2_AMD_ALIASES (CPUID_EXT2_FPU | CPUID_EXT2_VME | \
> -- 
> 1.9.0
>