On 10/12/21 15:37, Richard Biener wrote:
On Tue, Oct 12, 2021 at 2:18 PM Martin Liška <mli...@suse.cz> wrote:
Hello.
The option is disabled in rs6000 target with:
{ OPT_LEVELS_ALL, OPT_frename_registers, NULL, 0 },
Thus, we have to do an auto-detection only if it's really unset and also
equal to the Init value.
Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
And the problematic test-case works on ppc64le.
Ready to be installed?
Hmm, I can see how it fixes the reported problem but I think the
thing is fragile.
You are fully right, it's quite fragile.
I wonder if we can express things like
+ if (!OPTION_SET_P (flag_web))
flag_web = flag_unroll_loops;
or
+ if (!OPTION_SET_P (flag_rename_registers))
flag_rename_registers = flag_unroll_loops;
by adding EnabledBy(funroll-loops) to the respective options instead
(and funroll-loops EnabledBy(funroll-all-loops))
Testing that approach, I like it.
Note that my fix:
if (!OPTION_SET_P (flag_rename_registers) && flag_rename_registers)
won't work if one target sets flag_rename_registers = 1 and another to
flag_rename_registers = 0.
Then one can't use Init setting a proper default value.
All SET_OPTION_IF_UNSET are fragile with respect to target overrides
(-fprofile-use does a lot of those for example).
I suppose opts_set could also record whether the target overrided
sth with its option_optimization_table.
I can experiment with a patch where SET_OPTION_IF_UNSET modified opts_set.
Thanks for clever feedback.
Martin
Richard.
Thanks,
Martin
PR target/102688
gcc/ChangeLog:
* common.opt: Enable flag_rename_registers by default.
* toplev.c (process_options): Auto-detect flag_rename_registers
only if it is not turned off in a target.
---
gcc/common.opt | 2 +-
gcc/toplev.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/gcc/common.opt b/gcc/common.opt
index 4099effcc80..2c6be1bdd36 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2399,7 +2399,7 @@ Common Var(flag_live_range_shrinkage) Init(0) Optimization
Relief of register pressure through live range shrinkage.
frename-registers
-Common Var(flag_rename_registers) Optimization
+Common Var(flag_rename_registers) Init(1) Optimization
Perform a register renaming optimization pass.
fschedule-fusion
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 167feac2583..ee7d8854f90 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1335,7 +1335,8 @@ process_options (bool no_backend)
if (!OPTION_SET_P (flag_web))
flag_web = flag_unroll_loops;
- if (!OPTION_SET_P (flag_rename_registers))
+ /* The option can be turned off in a target. */
+ if (!OPTION_SET_P (flag_rename_registers) && flag_rename_registers)
flag_rename_registers = flag_unroll_loops;
if (flag_non_call_exceptions)
--
2.33.0
