On 4/29/24 08:59, Wilco Dijkstra wrote:
According to documentation, '^' should only have an effect during reload.
However ira-costs.cc treats it in the same way as '?' during early costing.
As a result using '^' can accidentally disable valid alternatives and cause
significant regressions (see PR114741). Avoid this by ignoring '^' during
costing.
Passes bootstrap and regress, OK for commit?
gcc:
PR rtl-optimization/114766
* ira-costs.cc (record_reg_classes): Ignore '^' during costing.
Sorry, I can not accept this patch. This constraint is used by other
targets (as I know rs6000, s390, sh, gcn). I suspect changing the
semantics can affect the targets in some undesirable way.
Saying that, I understand that aarch64 needs the new semantics. So I
think we can add a new hint with the required semantics. There are still
few undefined characters for the new hint: '~', '-', '/', and '.' (may
be I missed some),
I propose to use '~' for the new hint. So besides changing code, the
documentation for '^' needs to clarified and documentation for code '~'
should be added.
diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index
c86c5a16563aeefac9d4fa72839bee8d95409f4b..04d2f21b023f3456ba6f8c16c2418d7313965b2f
100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -771,10 +771,6 @@ record_reg_classes (int n_alts, int n_ops, rtx *ops,
c = *++p;
break;
- case '^':
- alt_cost += 2;
- break;
-
case '?':
alt_cost += 2;
break;
