From: Paolo Bonzini Date: Fri, 2 Sep 2016 15:36:23 +0000 (+0200) Subject: optionrom: do not rely on compiler's bswap optimization X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0342454f8aa6fc55e515bad26425533e10b58085;p=qemu.git optionrom: do not rely on compiler's bswap optimization Recent compilers can detect and inline manually-written bswap code, but GCC 4.2.1 (the last GPLv2 version) cannot and generates really awful code. Depending on how the compiler is configured, it might also not want to generate bswap because it was not in i386. Using asm is fine because TCG knows about bswap and all processors with virtualization extensions also do. Reported-by: Peter Maydell Signed-off-by: Paolo Bonzini --- diff --git a/pc-bios/linuxboot_dma.bin b/pc-bios/linuxboot_dma.bin index 238a195d38..218d3ab4a2 100644 Binary files a/pc-bios/linuxboot_dma.bin and b/pc-bios/linuxboot_dma.bin differ diff --git a/pc-bios/optionrom/linuxboot_dma.c b/pc-bios/optionrom/linuxboot_dma.c index 7549797732..4754282ad7 100644 --- a/pc-bios/optionrom/linuxboot_dma.c +++ b/pc-bios/optionrom/linuxboot_dma.c @@ -122,24 +122,14 @@ static inline void writel_es(uint16_t offset, uint32_t val) static inline uint32_t bswap32(uint32_t x) { - return - ((x & 0x000000ffU) << 24) | - ((x & 0x0000ff00U) << 8) | - ((x & 0x00ff0000U) >> 8) | - ((x & 0xff000000U) >> 24); + asm("bswapl %0" : "=r" (x) : "0" (x)); + return x; } static inline uint64_t bswap64(uint64_t x) { - return - ((x & 0x00000000000000ffULL) << 56) | - ((x & 0x000000000000ff00ULL) << 40) | - ((x & 0x0000000000ff0000ULL) << 24) | - ((x & 0x00000000ff000000ULL) << 8) | - ((x & 0x000000ff00000000ULL) >> 8) | - ((x & 0x0000ff0000000000ULL) >> 24) | - ((x & 0x00ff000000000000ULL) >> 40) | - ((x & 0xff00000000000000ULL) >> 56); + asm("bswapl %%eax; bswapl %%edx; xchg %%eax, %%edx" : "=A" (x) : "0" (x)); + return x; } static inline uint64_t cpu_to_be64(uint64_t x)