Re: [PATCH 2/2] x86/mce: Add quirk for instruction recovery on SandyBridge processors

From: Tony Luck
Date: Fri Jul 20 2012 - 12:33:18 EST

> Maybe define a default empty quirk_no_way_out() on the remaining
> families/vendors so that the compiler can optimize it away and we save
> ourselves the if-test?

Perhaps I misunderstood your suggestion. I don't see how the compiler will
manage to optimize it all away. I just tried defining

static void quirk_no_way_out_nop(int bank, struct mce *m, struct pt_regs *regs)

and providing that as an initial value for the quirk_no_way_out
function pointer.

Then I deleted the "if (quirk_no_way_out)".

Looking at the assembly code produced, I now just have an unconditional call:

callq *0x9fe992(%rip) # ffffffff81a18668 <quirk_no_way_out>

I'd think that a call through a function pointer to an empty function is
more expensive that testing whether that function pointer was NULL.

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