[Qemu-devel] [PULL 47/58] optionrom: do not rely on compiler's bswap optimization

[Paolo Bonzini]

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 <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
 pc-bios/linuxboot_dma.bin         | Bin 1536 -> 1536 bytes
 pc-bios/optionrom/linuxboot_dma.c |  18 ++++--------------
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/pc-bios/linuxboot_dma.bin b/pc-bios/linuxboot_dma.bin
index 
238a195d3869995067f158d243d852778d38a736..218d3ab4a29bfb5ab7125ec7a4d29dad1860c673
 100644
GIT binary patch
delta 339
zcmZqRY2cX<address@hidden)%0mw_QIIIZ(address@hidden;address@hidden)p8vn^O
z{?qAcoh~XIKr%#y2T1y;umDLJm9$+FtU&FZ4<`OnXBS9|PCJ}7VX^_Eq+#*@|Nqm|
zdR<fm(sr^i0F~?#2azwL!Q$O4Ae}&g^t5gtppq9Z|0h>5I!ZFabcw)paf5ZeoP33G
address@hidden|Ja#Es#jtB?z$$=!diyoG|q~F!jP<^&kI2&6k0R
mi-5&%g2lUqTvT|address@hidden>_jEn%58-ITQ

delta 431
zcmXwyy-Pw-7{<>{qpRJ}@<zvSJkji*5IDL;IYdRv<I?ETbQPyVTu2;RT8ftDT)NP3
z3|c~ph9rW>2)#oPZ9?Sj_1IY+UVhKVTXm|address@hidden;^g|K?zbJ)address@hidden)%
address@hidden;9Z$q}B-Z>JlP=hoQPpID~vBIc<{3Gh0E~VQP8$yK~wSk_R
address@hidden>C#XLxLl%WiS`iNEzKD~?1>_q7KFwI;Y&GR#3p?1wHg5bDp@(cf6Gc%O
zenF&h6{lGQOJfaxMq_?R0|6&MXOSY|$Edk%tz}QOOD)&5W_3$8E7r01{rkUZ8+S&#
z&xUiuZOxVD^nfFnpFArF8{vh?J0_pe`G(;+!(Gh}COZoS;UHL?3>8HV;ojxRR4itB
Ee=`xOo&W#<

diff --git a/pc-bios/optionrom/linuxboot_dma.c 
b/pc-bios/optionrom/linuxboot_dma.c
index 7549797..4754282 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)
-- 
1.8.3.1