RFR: JDK-8231583: Shenandoah fails with finagle-http

[Aleksey Shipilev]

On 9/30/19 3:12 PM, Roman Kennke wrote:
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8231583
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8231583/webrev.00/

Awww.

Please change the synopsis to reflect what is being done, not the symptom of it. Suggestion:
  Shenandoah: register clash in SBSA::resolve_forwarding_pointer borrowing

I believe we are better off just fixing the borrowing scheme, like (not heavily tested):

diff -r 6902d5acd5e8 src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp
--- a/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp   Mon Sep 30
10:19:03 2019 +0200
+++ b/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp   Mon Sep 30
15:30:52 2019 +0200
@@ -212,7 +212,12 @@
     // No free registers available. Make one useful.
     tmp = rscratch1;
+    if (tmp == dst) {
+      tmp = rscratch2;
+    }
     __ push(RegSet::of(tmp), sp);
   }

+  assert_different_registers(tmp, dst);
+
   Label done;
   __ ldr(tmp, Address(dst, oopDesc::mark_offset_in_bytes()));
diff -r 6902d5acd5e8 src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp
--- a/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp   Mon Sep 30 10:19:03
2019 +0200
+++ b/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp   Mon Sep 30 15:30:52
2019 +0200
@@ -272,7 +272,12 @@
     // No free registers available. Make one useful.
     tmp = LP64_ONLY(rscratch1) NOT_LP64(rdx);
+    if (tmp == dst) {
+      tmp = LP64_ONLY(rscratch2) NOT_LP64(rcx);
+    }
     __ push(tmp);
   }

+  assert_different_registers(dst, tmp);
+
   Label done;
   __ movptr(tmp, Address(dst, oopDesc::mark_offset_in_bytes()));


-- 
Thanks,
-Aleksey