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Downgoat

00:01

halp how to declare variable length array in llvm

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00:40

@Downgoat groups.google.com/forum/#!topic/llvm-dev/k4eR4MzDZdM

alloca

Downgoat

well yeah

but do i do a mul to get the length

that doesn't seem right

I could do array of pointers

but that is not always best solutoni

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@Downgoat llvm has no better solution

Downgoat

can't be right

I checked clangs output and it doesn't do that

well actually i have idea

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@Downgoat pls show clang's output?

clang probably calls C malloc instead

Downgoat

it uses zest

malloc is too heavy dependency

also complicated memory mangement

ok I have this so far:

; VSL LLVM IR. v1.0
source_filename = "#filename"

; @0 = c-string
; @1 = lengt
%String = type { i8*, i8 }

define i32 @main(i32, i8**) {
entry:
    %i1 = alloca i32, align 4
    jp at1
r1:


at1:
    %iv = load i32, i32* %i1, align 4
    %i2 = add nsw i32 %iv, i32 1
    %i3 = store i32 %i2, i32* %i1, align 4
    %i4 = icmp slt i32 %i3, i32 %0
    br i1 %i4, %label r1

    call void @entry(%.args)
    ret 0
}

define void @entry(%String*) {
entry:
    ; #source
    ret void
}

%String is obviously temporary

oh wait this is simple

I can just zest it

shit have to handle 64-bit v 32-bit

halp how to do

ASCII-only

00:51

@Downgoat two different llvm generators

Downgoat

nah

we can just have mem_t

or equivilient

for 32-bit will be mem_t = i32

but actually

we might have to do some more zesting

llvm should of not named functions sext and zest

0/10 bad idea

ASCII-only

what is zest

Downgoat

expand int type, left-filling 0s, signed w/ 0,1 overflow

actually looks as simple as:

  %42 = getelementptr inbounds %struct.String, %struct.String* %4, i64 %41, i32 1
  store i32 0, i32* %42, align 8, !tbaa !1
  %43 = add nsw i64 %29, 7

:O VSL is already faster than C

:O @PhiNotPi has his own LLVM instruction

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@Downgoat O.o where

Downgoat

llvm.org/docs/LangRef.html#phi-instruction

pls halp understand because gaot does not understand wat instruction does tho ;_;

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01:01

Static single assignment form

In compiler design, static single assignment form (often abbreviated as SSA form or simply SSA) is a property of an intermediate representation (IR), which requires that each variable is assigned exactly once, and every variable is defined before it is used. Existing variables in the original IR are split into versions, new variables typically indicated by the original name with a subscript in textbooks, so that every definition gets its own version. In SSA form, use-def chains are explicit and each contains a single element. SSA was developed by Ron Cytron, Jeanne Ferrante, Barry K. Rosen, Mark...

switch-case value based on last executed block (in that case Loop or LoopHeader)

Downgoat

wat

wat is swich case value

ASCII-only

ok so basically

%indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ] means:

if %last_executed_block == %LoopHeader:
    %indvar = 0
else if %last_executed_block == %Loop:
    %indvar = %nextindvar

Downgoat

wat wow 10/10 vrey helpful

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@Downgoat ?

Downgoat

halp how to sizeof in LLVM

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01:08

Q: How can I find the size of a type?

I'm holding a Type* in my hand. How do I find out its size (the size objects of this type will occupy in memory) in bits / bytes? I see all kinds of methods allowing me to get "primitive" or "scalar" size, but that won't help me with aggregate types...

llvm

Downgoat

sorry, sizeof pointer

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well i'm pretty sure c hardcodes sizeof values, idk

Downgoat

not possible

I am trying to get length of argc

ASCII-only

@Downgoat then ^^^^^

Downgoat

type != pointer

ASCII-only

01:14

@Downgoat ok then idk

that should still work for pointer though i think

Downgoat

can't make 0 sense

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@Downgoat ???

Downgoat

they are doing int size = (int) *pointer

pls halp solve problem major bottleneck

here is progress:

; VSL LLVM IR. v1.0
source_filename = "#filename"

; @0 char* = c-string
; @1 int   = length
@class.String = type { i8*, i32 }

define i32 @main(i32, i8**) {
entry:
    %.args = alloca @class.String, i32 %0, align 16
    %i1 = alloca i32, align 4
    jp at1
r1:
    %i5 = load i32, i32* %i1, align 4
    ;String*[i32: index, %i5][i32 1: length]
    %i6 = getelementptr inbounds @class.String, @class.String* %.args, i64 %i5, i32 1
    %i7 = <somehow calculate sizeof the char>
    store i32 %i7, i32 %i6, align 8

22 hours later…

Downgoat

23:53

@ASCII-only hello

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