gistfile1.txt

; declare { printf } = @cimport(@cinclude("stdio.h"))
;
; fn square(num: i32) { 
;   #start: {
;     let #safe_mult = num *? num
;     let [ #mult_val, #was_safe ] = #safe_mult
;     let #should_panic = #was_safe == false
;     #should_panic ? goto #panic : goto #return
;   }
;
;  #panic: {
;    // @panic(`info`)
;    unreachable
;  }
;
;  #return: {
;    return #mult_value
;  }
; }
;
; fn main {
;   #start: {
;     #square_result = square(56)
;     printf("%d", #square_result)
;     goto #return
;   }
;   
;   #return: {
;     return void
;   }
; }


declare i32 @printf(i8*, ...)

define i32 @square(i32 %num) {
  start:
    %safe_mult = call { i32, i1 } @llvm.smul.with.overflow.i32(i32 %num, i32 %num)

    %mult_val = extractvalue { i32, i1 } %safe_mult, 0
    %was_safe = extractvalue { i32, i1 } %safe_mult, 1

    %should_panic = call i1 @llvm.expect.i1(i1 %was_safe, i1 false)

    br i1 %should_panic, label %panic, label %return

  panic:
    ; call @panic message
    unreachable

  return:
    ret i32 %mult_val
}

@.str = private unnamed_addr constant [3 x i8] c"%d\00", align 1

define void @main() {
  start:
    %square_result = call i32 @square (i32 36)
    call i32 (i8*, ...) @printf(i8* getelementptr ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32 %square_result)
    br label %return

  return:
    ret void
}

declare i1 @llvm.expect.i1(i1, i1)
declare { i32, i1 } @llvm.smul.with.overflow.i32(i32, i32)