| Message ID | 20230331051129.2691249-1-hongtao.liu@intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | Adjust memory_move_cost for MASK_REGS when MODE_SIZE > 8. | expand |
On Fri, Mar 31, 2023 at 7:11 AM liuhongt <hongtao.liu@intel.com> wrote: > > RA sometimes will use lowest the cost of the mode with all different regclasses > w/o check if it's hard_regno_mode_ok. > It's impossible to put modes whose size > 8 into MASK_REGS, ajdust the cost to > avoid potential performance issue. I was going to ask to open a PR in order to fix RA instead of the proposed workaround, but the patch just prevents a theoretical issue and follows the established practice with other regclasses. Perhaps these workarounds are not needed with the current RA, but this is a tangential issue which should be fixed for all regclasses. > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}. > Ok for trunk? OK. Thanks, Uros. > > gcc/ChangeLog: > > * config/i386/i386.cc (inline_memory_move_cost): Return 100 > for MASK_REGS when MODE_SIZE > 8. > --- > gcc/config/i386/i386.cc | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc > index 2cc8e9548a9..2581b800a06 100644 > --- a/gcc/config/i386/i386.cc > +++ b/gcc/config/i386/i386.cc > @@ -19847,9 +19847,12 @@ inline_memory_move_cost (machine_mode mode, enum reg_class regclass, int in) > index = 1; > break; > /* DImode loads and stores assumed to cost the same as SImode. */ > - default: > + case 4: > + case 8: > index = 2; > break; > + default: > + return 100; > } > > if (in == 2) > -- > 2.39.1.388.g2fc9e9ca3c >
On Fri, Mar 31, 2023 at 1:57 PM Uros Bizjak <ubizjak@gmail.com> wrote: > > On Fri, Mar 31, 2023 at 7:11 AM liuhongt <hongtao.liu@intel.com> wrote: > > > > RA sometimes will use lowest the cost of the mode with all different regclasses > > w/o check if it's hard_regno_mode_ok. > > It's impossible to put modes whose size > 8 into MASK_REGS, ajdust the cost to > > avoid potential performance issue. > > I was going to ask to open a PR in order to fix RA instead of the > proposed workaround, but the patch just prevents a theoretical issue > and follows the established practice with other regclasses. Perhaps > these workarounds are not needed with the current RA, but this is a > tangential issue which should be fixed for all regclasses. Opened https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109351 > > > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}. > > Ok for trunk? > > OK. > > Thanks, > Uros. > > > > > gcc/ChangeLog: > > > > * config/i386/i386.cc (inline_memory_move_cost): Return 100 > > for MASK_REGS when MODE_SIZE > 8. > > --- > > gcc/config/i386/i386.cc | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc > > index 2cc8e9548a9..2581b800a06 100644 > > --- a/gcc/config/i386/i386.cc > > +++ b/gcc/config/i386/i386.cc > > @@ -19847,9 +19847,12 @@ inline_memory_move_cost (machine_mode mode, enum reg_class regclass, int in) > > index = 1; > > break; > > /* DImode loads and stores assumed to cost the same as SImode. */ > > - default: > > + case 4: > > + case 8: > > index = 2; > > break; > > + default: > > + return 100; > > } > > > > if (in == 2) > > -- > > 2.39.1.388.g2fc9e9ca3c > >
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index 2cc8e9548a9..2581b800a06 100644 --- a/gcc/config/i386/i386.cc +++ b/gcc/config/i386/i386.cc @@ -19847,9 +19847,12 @@ inline_memory_move_cost (machine_mode mode, enum reg_class regclass, int in) index = 1; break; /* DImode loads and stores assumed to cost the same as SImode. */ - default: + case 4: + case 8: index = 2; break; + default: + return 100; } if (in == 2)
RA sometimes will use lowest the cost of the mode with all different regclasses w/o check if it's hard_regno_mode_ok. It's impossible to put modes whose size > 8 into MASK_REGS, ajdust the cost to avoid potential performance issue. Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}. Ok for trunk? gcc/ChangeLog: * config/i386/i386.cc (inline_memory_move_cost): Return 100 for MASK_REGS when MODE_SIZE > 8. --- gcc/config/i386/i386.cc | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)