x86: 64 bits: shrink and align IRQ stubs

Move the IRQ stub generation to assembly to simplify it and for
consistency with 32 bits.  Doing it in a C file with asm() statements
doesn't help clarity, and it prevents some optimizations.

Shrink the IRQ stubs down to just over four bytes per (we fit seven
into a 32-byte chunk.)  This shrinks the total icache consumption of
the IRQ stubs down to an even kilobyte, if all of them are in active
use.

The downside is that we end up with a double jump, which could have a
negative effect on some pipelines.  The double jump is always inside
the same cacheline on any modern chips.

To get the most effect, cache-align the IRQ stubs.

This makes the 64-bit code match changes already done to the 32-bit
code, and should open up irqinit*.c for unification.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 27d33f92afe2..8de644b6b959 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -109,9 +109,7 @@ extern asmlinkage void smp_invalidate_interrupt(struct pt_regs *);
 #endif
 #endif
 
-#ifdef CONFIG_X86_32
 extern void (*__initconst interrupt[NR_VECTORS-FIRST_EXTERNAL_VECTOR])(void);
-#endif
 
 typedef int vector_irq_t[NR_VECTORS];
 DECLARE_PER_CPU(vector_irq_t, vector_irq);