PPC/s390: [write-barrier] Add debug check for cleared weak refs in write barrier

Port dbff2a67

R=dmercadier@chromium.org, joransiu@ca.ibm.com, junyan@redhat.com, midawson@redhat.com
BUG=
LOG=N

Change-Id: I6b34e6cd502012474c619bbcb1e473ee4f7472db
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3564278Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#79696}

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -1112,6 +1112,13 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       Register scratch1 = i.TempRegister(1);
       OutOfLineRecordWrite* ool;
 
+      if (FLAG_debug_code) {
+        // Checking that |value| is not a cleared weakref: our write barrier
+        // does not support that for now.
+        __ CmpS64(value, Operand(kClearedWeakHeapObjectLower32), kScratchReg);
+        __ Check(ne, AbortReason::kOperandIsCleared);
+      }
+
       AddressingMode addressing_mode =
           AddressingModeField::decode(instr->opcode());
       if (addressing_mode == kMode_MRI) {

src/compiler/backend/s390/code-generator-s390.cc

@@ -1427,6 +1427,13 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       Register scratch1 = i.TempRegister(1);
       OutOfLineRecordWrite* ool;
 
+      if (FLAG_debug_code) {
+        // Checking that |value| is not a cleared weakref: our write barrier
+        // does not support that for now.
+        __ CmpS64(value, Operand(kClearedWeakHeapObjectLower32));
+        __ Check(ne, AbortReason::kOperandIsCleared);
+      }
+
       AddressingMode addressing_mode =
           AddressingModeField::decode(instr->opcode());
       if (addressing_mode == kMode_MRI) {