Re: [10/32] Remove global call sets: combine.c

[Richard Sandiford]

Segher Boessenkool <seg...@kernel.crashing.org> writes:
> Hi Richard,
>
> Sorry this too me so long to get back to.
>
> On Thu, Sep 12, 2019 at 08:51:59AM +0100, Richard Sandiford wrote:
>> Segher Boessenkool <seg...@kernel.crashing.org> writes:
>> > On Wed, Sep 11, 2019 at 08:08:38PM +0100, Richard Sandiford wrote:
>> >>        hard_reg_set_iterator hrsi;
>> >> -      EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call, 0, i, 
>> >> hrsi)
>> >> +      EXECUTE_IF_SET_IN_HARD_REG_SET (abi.full_and_partial_reg_clobbers 
>> >> (),
>> >> +                               0, i, hrsi)
>> >
>> > So "abi" in that means calls?
>> 
>> "abi" is the interface of the callee function, taking things like
>> function attributes and -fipa-ra into account.
>> 
>> The register sets are describing what the callee does rather than
>> what calls to it do.  E.g. on targets that allow linker stubs to be
>> inserted between calls, the scratch registers reserved for linker stubs
>> are still call-clobbered, even if the target of the call doesn't use
>> them.  (Those call clobbers are represented separately, at least when
>> TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS is true.  When it's
>> false we don't use -fipa-ra information at all.)
>> 
>> > It is not such a great name like that.  Since its children are
>> > very_long_names, it doesn't need to be only three chars itself,
>> > either?
>> 
>> OK, what name would you prefer?
>
> Maybe call_abi is a good name?  It's difficult to capture the subtleties
> in a short enough name.  As always :-)

The formatting ended up being a bit weird with a longer name,
so how about the attached instead?

Richard


2019-09-25  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        * combine.c: Include function-abi.h.
        (record_dead_and_set_regs): Use insn_callee_abi to get the ABI
        of the target of call insns.  Invalidate partially-clobbered
        registers as well as fully-clobbered ones.

Index: gcc/combine.c
===================================================================
--- gcc/combine.c       2019-09-12 10:52:53.000000000 +0100
+++ gcc/combine.c       2019-09-25 16:50:21.772865265 +0100
@@ -105,6 +105,7 @@ Software Foundation; either version 3, o
 #include "valtrack.h"
 #include "rtl-iter.h"
 #include "print-rtl.h"
+#include "function-abi.h"
 
 /* Number of attempts to combine instructions in this function.  */
 
@@ -13464,11 +13465,21 @@ record_dead_and_set_regs (rtx_insn *insn
 
   if (CALL_P (insn))
     {
+      HARD_REG_SET callee_clobbers
+       = insn_callee_abi (insn).full_and_partial_reg_clobbers ();
       hard_reg_set_iterator hrsi;
-      EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call, 0, i, hrsi)
+      EXECUTE_IF_SET_IN_HARD_REG_SET (callee_clobbers, 0, i, hrsi)
        {
          reg_stat_type *rsp;
 
+         /* ??? We could try to preserve some information from the last
+            set of register I if the call doesn't actually clobber
+            (reg:last_set_mode I), which might be true for ABIs with
+            partial clobbers.  However, it would be difficult to
+            update last_set_nonzero_bits and last_sign_bit_copies
+            to account for the part of I that actually was clobbered.
+            It wouldn't help much anyway, since we rarely see this
+            situation before RA.  */
          rsp = &reg_stat[i];
          rsp->last_set_invalid = 1;
          rsp->last_set = insn;