Home/ Questions/Q 8351947
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-09T08:48:21+00:00

I am learning assembly and making some inlining in my Digital Mars C++ compiler.

  • 0

I am learning assembly and making some inlining in my Digital Mars C++ compiler. I searched some things to make a program better and had these parameters to tune the programs:

use better C++ compiler//thinking of GCC or intel compiler

use assembly only in critical part of program 

find better algorithm

Cache miss, cache contention.

Loop-carried dependency chain.

Instruction fetching time.

Instruction decoding time.

Instruction retirement.

Register read stalls.

Execution port throughput.

Execution unit throughput.

Suboptimal reordering and scheduling of micro-ops.

Branch misprediction.

Floating point exception.

I understood all except “register read stalls”.

Question: Can anybody tell me how is this happening in CPU and the “superscalar” form of the “out of order execution”?
Normal “out of order” seemed logical but i couldnt find a logical explanation of “superscalar” form.

Question 2: Can someone alse give some good instruction list of SSE SSE2 and newer CPU’s prefarably with micro-ops table, port throughputs, units and some calculation table for the latencies to find the real bottle-neck of a piece of code?

I would be happy with a small example like this:

//loop carried dependency chain breaking:
__asm
{
loop_begin:
....
.... 
sub edx,05h //rather than taking i*5 in each iteration, we sub 5 each iteration
sub ecx,01h //i-- counter
...
...
jnz loop_begin//edit: sub ecx must have been after the sub edx for jnz
}
//while sub edx makes us get rid of a multiplication also makes that independent of ecx, making independent

Thank you.

Computer: Pentium-M 2GHz , Windows XP-32 bit

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You should take a look at Agner Fogs optimization manuals: Optimizing software in C++: An optimization guide for Windows, Linux and Mac platforms or Optimizing subroutines in assembly language: An optimization guide for x86 platforms.

    But to really be able to outsmart a modern compiler, you need some good background knowledge of the arch you want to optimize for: The microarchitecture of Intel, AMD and VIA CPUs: An optimization guide for assembly programmers and compiler makers

    • 0