PPC/s390: [wasm][liftoff] Fix and cleanup tracing of return value

Port 6f9e71fa

Original Commit Message:

    - Fix tracing of reference return values. StoreTaggedPointer should not
      use the write barrier since we are writing to the stack.
    - Avoid re-allocating a slot for the return value when it is already
      spilled.

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

Change-Id: I5b16259b1c6e8c019f6b17e8efb7947776e4ee24
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3886398Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#83112}

src/wasm/baseline/ppc/liftoff-assembler-ppc.h

@@ -1093,6 +1093,10 @@ void LiftoffAssembler::FillStackSlotsWithZero(int start, int size) {
   }
 }
 
+void LiftoffAssembler::LoadSpillAddress(Register dst, int offset) {
+  SubS64(dst, fp, Operand(offset));
+}
+
 #define SIGN_EXT(r) extsw(r, r)
 #define ROUND_F64_TO_F32(fpr) frsp(fpr, fpr)
 #define INT32_AND_WITH_1F(x) Operand(x & 0x1f)

src/wasm/baseline/s390/liftoff-assembler-s390.h

@@ -1552,6 +1552,10 @@ void LiftoffAssembler::FillStackSlotsWithZero(int start, int size) {
   pop(r0);
 }
 
+void LiftoffAssembler::LoadSpillAddress(Register dst, int offset) {
+  SubS64(dst, fp, Operand(offset));
+}
+
 #define SIGN_EXT(r) lgfr(r, r)
 #define INT32_AND_WITH_1F(x) Operand(x & 0x1f)
 #define REGISTER_AND_WITH_1F    \