Hello Liming,
I did some tests and this is what I found. All test are for 32-bit code
generation only.
VS2012 and VS2013 both default to /arch:SSE2. Older Microsoft compilers default
to /arch:IA32.
With /arch:IA32, floating point operations are done using the old x87 fpu
registers.
Converting from double to unsigned int is done using the FIST (floating integer
store) instruction.
With arch:SSE2, floating point operations are mostly handled by SSE2
instructions. But there
is a difference between VS2012 /arch:SSE2 and VS2013 /arch:SSE2. With VS2012
/arch:SSE2,
conversion from double to unsigned integer is still done using the x87 fpu FIST
instruction.
But with VS2013, conversion from double to unsigned integer is done by calling
__dtoui3.
Here is an example:
float.c: unsigned test (double d) {return (unsigned int) d;}
cl -c /arch:SSE2 -Ox /FAsc float.c
VS2013 float.cod:
--------------------------------------------------------------
00000 f2 0f 10 44 24 04 movsd xmm0, QWORD PTR _d$[esp-4]
00006 e9 00 00 00 00 jmp __dtoui3
--------------------------------------------------------------
VS2012 float.cod:
--------------------------------------------------------------
00000 83 ec 08 sub esp, 8
00003 dd 44 24 0c fld QWORD PTR _d$[esp+4]
00007 d9 7c 24 0c fnstcw WORD PTR tv66[esp+4]
0000b 0f b7 44 24 0c movzx eax, WORD PTR tv66[esp+4]
00010 0d 00 0c 00 00 or eax, 3072 ; 00000c00H
00015 89 04 24 mov DWORD PTR tv69[esp+8], eax
00018 d9 2c 24 fldcw WORD PTR tv69[esp+8]
0001b df 3c 24 fistp QWORD PTR tv71[esp+8]
0001e 8b 04 24 mov eax, DWORD PTR tv71[esp+8]
00021 d9 6c 24 0c fldcw WORD PTR tv66[esp+4]
00025 83 c4 08 add esp, 8
00028 c3 ret 0
--------------------------------------------------------------
Thanks,
Scott
-----Original Message-----
From: Gao, Liming [mailto:[email protected]]
Sent: Monday, September 15, 2014 09:29 AM
To: [email protected]
Subject: Re: [edk2] [patch 2/5] AppPkg: fix IA32 build failure when VS2013 tool
chain is used
MSDN says the default is /arch:SSE2 if /arch is not specified for VS2013. Do
you mean old Microsoft tool chain use /arch:SSE as the
default option?
-----Original Message-----
From: Scott Duplichan [mailto:[email protected]]
Sent: Monday, September 15, 2014 12:03 PM
To: [email protected]
Subject: [edk2] [patch 2/5] AppPkg: fix IA32 build failure when VS2013 tool
chain is used
AppPkg: fix IA32 build failure when VS2013 tool chain is used.
The build fails due to link error 2001, unresolved external symbol __dtoui3.
Avoid this error by using /arch:SSE code generation flag for VS2013 IA32
compiles.
This overrides the VS2013 default code generation option of /arch:SSE2, making
it match older Microsoft tool chains. While SSE2 can
improve performance of floating point intensive applications, UEFI code uses
little floating point, and no performance impact is
expected.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Scott Duplichan <[email protected]>
--
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