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NEON vdiv.f32 syntax
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NEON vdiv.f32 syntax
Carl van Heezik
over 10 years ago
Note: This was originally posted on 17th April 2012 at
http://forums.arm.com
I am (re)coding a 3D math library with inline NEON assembly for iOS using the Apple LLVM compiler 3.1.
I get an error message on the following instruction:
[color="#000000"] "vdiv.f32 q0, q1, q2 \n\t" [/color]
VFP single or double precision register expected -- `vdiv.f32 q0,q1,q2'
According to the 'Assembler Reference' page 4-76 you should specify a single precision register. The following code works:
[color="#000000"] "vdiv.f32 s0, s4, s8 \n\t" [/color]
"vdiv.f32 s1, s5, s9 \n\t"
"vdiv.f32 s2, s6, s10 \n\t"
I am confused because now the divide is not computed in parallel, which was the reason to use inline assembly.
Also the following instructions work as expected:
[color="#000000"] // component wise add[/color]
[color="#000000"] "vadd.f32 q0, q1, q2 \n\t" [/color]
[color="#008311"] // component wise subtract
[color="#000000"] "vsub.f32 q0, q1, q2 \n\t" [/color]
[color="#008311"] // component wise multiply
[color="#000000"] "vmul.f32 q0, q1, q2 \n\t" [/color][/color][/color]
[color="#000000"]
[color="#ce2f24"][color="#000000"]Why do I get an error message on the vdiv and not on the vadd, vsub and vmul? Is this a compiler error?[/color]
[/color][/color]
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Etienne SOBOLE
over 10 years ago
Note: This was originally posted on 17th April 2012 at
http://forums.arm.com
I see the problem
Use this PDF documentation instead
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0406c/index.html
chapter A8.8.312
It's said "Encoding T1/A1 VFPv2, VFPv3, VFPv4"
VDIV is not a NEON instruction.
Vpf and NEON are not the same computing unit.
ARM have decided to unify the instruction syntax but the two unit are very different !!!
Etienne
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Etienne SOBOLE
over 10 years ago
Note: This was originally posted on 17th April 2012 at
http://forums.arm.com
I see the problem
Use this PDF documentation instead
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0406c/index.html
chapter A8.8.312
It's said "Encoding T1/A1 VFPv2, VFPv3, VFPv4"
VDIV is not a NEON instruction.
Vpf and NEON are not the same computing unit.
ARM have decided to unify the instruction syntax but the two unit are very different !!!
Etienne
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