Sum all elements in a quadword vector in ARM assembly with NEON

math assembly arm neon
A Person picture A Person · Aug 3, 2011 · Viewed 9.5k times · Source

Im rather new to assembly and although the arm information center is often helpful sometimes the instructions can be a little confusing to a newbie. Basically what I need to do is sum 4 float values in a quadword register and store the result in a single precision register. I think the instruction VPADD can do what I need but I'm not quite sure.

Answer

Krystian Bigaj picture Krystian Bigaj · Aug 3, 2011

You might try this (it's not in ASM, but you should be able to convert it easily):

float32x2_t r = vadd_f32(vget_high_f32(m_type), vget_low_f32(m_type));
return vget_lane_f32(vpadd_f32(r, r), 0);

In ASM it would be probably only VADD and VPADD.

I'm not sure if this is only one method to do this (and most optimal), but I haven't figured/found better one...

PS. I'm new to NEON too

Related questions

Overflow and Carry flags on Z80

I have gotten round to implementing the ADD A,r set of opcodes on my Z80 core. I had a bit of confusion about the carry and overflow flags which I think I've nailed, but I wanted to put it …

Read More
How can I perform 64-bit division with a 32-bit divide instruction?

This is (AFAIK) a specific question within this general topic. Here's the situation: I have an embedded system (a video game console) based on a 32-bit RISC microcontroller (a variant of NEC's V810). I want to write a fixed-point math …

Read More
How can I check for NaN values?

float('nan') results in Nan (not a number). But how do I check for it? Should be very easy, but I cannot find it.

Read More