[Bug rtl-optimization/115912] [15 regression] Harfbuzz testsuite fails (mvar_partial_instance test) since r15-1901-g98914f9eba5f19

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115912

--- Comment #14 from Sam James <sjames at gcc dot gnu.org> ---
```
--- a/libharfbuzz_subset_la-hb-subset.cc.300r.ext_dce
+++ b/libharfbuzz_subset_la-hb-subset.cc.300r.ext_dce
@@ -299442,7 +299442,6 @@ Processing insn:
       REG_DEAD r481:SI
 Trying to simplify pattern:
 (zero_extend:SI (subreg:HI (reg:SI 481) 0))
-***dbgcnt: upper limit 31 reached for ext_dce.***
 rescanning insn with uid = 376.
 Successfully transformed to:
 (reg:SI 481)
@@ -299452,7 +299451,11 @@ Processing insn:
       REG_DEAD r477:SI
 Trying to simplify pattern:
 (zero_extend:SI (subreg:HI (reg:SI 477) 0))
-Rejected due to debug counter.
+***dbgcnt: upper limit 32 reached for ext_dce.***
+rescanning insn with uid = 368.
+Successfully transformed to:
+(reg:SI 477)
+
 Processing insn:
   287: r450:SI=zero_extend(r207:SI#0)
       REG_DEAD r207:SI
@@ -301443,7 +301446,7 @@ Dataflow summary:
      (expr_list:REG_DEAD (reg:SF 266 [ _350 ])
         (nil)))
 (insn # # # 31 (set (reg:SI 613 [ _351 ])
-        (zero_extend:SI (subreg:HI (reg:SI 477) 0)))
"../../src/hb-algs.hh":125:52# {*zero_extendhisi2}
+        (reg:SI 477)) "../../src/hb-algs.hh":125:52# {*movsi_internal}
      (expr_list:REG_DEAD (reg:SI 477)
         (nil)))
 (insn # # # 31 (set (reg:HI 270 [ _354 ])
```