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Simulate SHL and SHR ASM instructions in Python

By : Moon Sun
Date : October 18 2020, 08:10 AM
will be helpful for those in need For variable-count shifts, don't forget to mask the shift-count as well. shl / shr only look at the low bits of cl. Same for bts reg,reg or reg,imm, and for BMI2 shlx r64, r64/m64, r64.
Either cl & 0x3f for 64-bit shifts, or cl & 0x1f for 32, 16, or 8-bit shifts. (So 16 and 8-bit shifts can zero an 8 or 16-bit register by shifting out all the bits). See the Operation section of the manual for pseudocode: http://felixcloutier.com/x86/SAL:SAR:SHL:SHR.html
code :
result = (input << 0x10) & 0xffffffffffffffff

result = (input << (cl & 0x3f)) & 0xffffffffffffffff

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Strange results for profiled executed instructions and issued instructions in Fermi GPU (GTX 580)

By : user3265743
Date : March 29 2020, 07:55 AM
will be helpful for those in need PTX is only an intermediate representation of compiled code. It is not what the GPU actually executes. There is a further assembly step which emits the code which the GPU runs, this can happen either at compile time, or using JIT compilation in the driver. As a result, your instruction counts and anything you infer from them are invalid.
NVIDIA ship a tool called cuobjdump which can disassemble the assembler output generated for Fermi cards and show the actual machine code run on the GPU

Instructions.m (instructions for the game) are not printing out the instructions?

By : Adam Koszegi
Date : March 29 2020, 07:55 AM
it fixes the issue NSLog does nothing on the screen. It just prints your text in Xcode's console.
To display text in the screen, try making a label. Like this:
code :
- (void) how
    // Create the label
    CCLabelTTF *label = [CCLabelTTF labelWithString:@"The object of this game is..." fontName:@"Arial" fontSize:30];

    // Position it on the screen
    label.position = ccp(160,240);

    // Add it to the scene so it can be displayed
    [self addChild:label z:0];

Why are bgezal & bltzal basic instructions and not pseudo-instructions in MIPS?

By : Lei ta
Date : March 29 2020, 07:55 AM
should help you out jal uses a semi-absolute target encoding (replacing the low 28 bits of PC), while bgezal / bltzal are relative (adding an 18-bit signed displacement, imm16<<2). How to Calculate Jump Target Address and Branch Target Address?
They are classic MIPS's only branch-and-link (instead of jump-and-link), so are important for position-independent relocatable code. (You can even use one to get the current PC into a register and find out where you're executing from, unlike with jal).
code :
0000 01ss sss1 0001 iiii iiii iiii iiii   BGEZAL
0000 01ss sss1 0000 iiii iiii iiii iiii   BLTZAL

What are the control instructions and move instructions latency for Intel's newer architectures?

By : Vids Patel
Date : March 29 2020, 07:55 AM
wish helps you The short answer is that latency is not really a meaningful metric in practice for control instructions, and for many types of mov instructions in isolation.
In the comments you mention:
code :
add eax, eax
add eax, eax
add eax, eax

Perf Reports Some Direct Jump Instructions as Memory Access Instructions

By : user3598502
Date : March 29 2020, 07:55 AM
To fix this issue On Intel CPUs at least, cmp %rax,(%rdx) can macro-fuse with the following je, while also micro-fusing the load. https://agner.org/optimize/. Also related: Micro fusion and addressing modes (this is a non-indexed addressing mode so this can stay micro-fused even on Sandybridge/IvyBridge).
So in the fused domain (where retirement happens) you really do have single-uop compare-and-branch with a memory source. Note that mem_load_uops_retired.l3_miss:uppp counts uops, not instructions.
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