Impact of Spectre on Julia?

Internals & Design
4

Ah, but julia does emit a lot of indirect jumps (callq) even if the target should be known. Simple example on 0.6:

f(V,i)=V[i]

X=rand(4)
@code_native f(X,2)

	.text
	leaq	-1(%rsi), %rax
	cmpq	24(%rdi), %rax
	jae	L20
	movq	(%rdi), %rax
	vmovsd	-8(%rax,%rsi,8), %xmm0  # xmm0 = mem[0],zero
	retq
L20:
	pushq	%rbp
	movq	%rsp, %rbp
	movq	%rsp, %rcx
	leaq	-16(%rcx), %rax
	movq	%rax, %rsp
	movq	%rsi, -16(%rcx)
	movabsq	$jl_bounds_error_ints, %rcx
	movl	$1, %edx
	movq	%rax, %rsi
	callq	*%rcx
	nopw	(%rax,%rax)

This code is vulnerable to spectre. I can mistrain the branch predictor to assume that the bound-check fails (jae) and mistrain the branch-target-predictor to jump (callq) to my favorite gadget.

Edit: Technically, this chains attacks 1 and 2 in the google terminology.

Edit 2: Maybe these indirect calls are worth fixing anyway, and should even improve performance (in a mostly negligible way, mostly reducing codesize and speeding up exceptions). No reason for codegen to not emit a direct call (we know which exception we want to raise).