On Tue, Sep 29, 2015 at 2:23 PM, Mike Stump <mikest...@comcast.net> wrote:
> On Sep 29, 2015, at 1:59 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>> commit f3a6675a8d69d810d2cad0c090a762094a0a8622
>> Author: H.J. Lu <hjl.to...@gmail.com>
>> Date: Tue Sep 29 13:47:18 2015 -0700
>>
>> Define EPILOGUE_USES in i386 so that all preserved registers are used
>> by the epilogue of interrupt handler. Don't explicitly mark BP and SP
>> registers as used since they are always used in epilogue.
>>
>> Please take a look.
>
> Oh, too bad you didn’t copy it here. The easiest thing to blow is the
> addition of reload_completed && on the condition:
>
> /* An interrupt handler must preserve some registers that are
> ordinarily call-clobbered. */
> if (reload_completed
> && myarch_interrupt_func (current_function_decl)
> && save_reg_p (regno))
> return true;
>
> without it, the optimizer will blow chunks all over the place and code-gen
> will not be very good, if it doesn’t. I’d love this to be shared across all
> ports, it it is cryptic and usually test cases are not elaborate enough to
> find the problem. When we ported a large library to our system that made
> extensive uses of complex interrupt routines, the compiler blew chunks. With
> lessor code, we never even noticed a problem.
We have
static bool
ix86_save_reg (unsigned int regno, bool maybe_eh_return)
{
/* In interrupt handler, we don't preserve MMX and x87 registers
which aren't supported when saving and restoring registers. No
need to preserve callee-saved registers unless they are modified.
We also preserve all caller-saved registers if a function call
is made in interrupt handler since the called function may change
them. Don't explicitly save BP and SP registers since they are
always preserved. */
if (cfun->machine->is_interrupt)
return ((df_regs_ever_live_p (regno)
|| (call_used_regs[regno] && cfun->machine->make_calls))
&& !fixed_regs[regno]
&& !STACK_REGNO_P (regno)
&& !MMX_REGNO_P (regno)
&& regno != BP_REG
&& regno != SP_REG
&& (regno <= ST7_REG || regno >= XMM0_REG));
Is this sufficient?
--
H.J.
