PPC: [compiler] Add relocatable pointer constants for wasm memory references.

Port eb5fe0df

Original commit message:
    Add relocatable pointers for wasm memory references that need to
    be updated when wasm GrowMemory is used. Code generator changes to
    accept relocatable constants as immediates.

R=gdeepti@google.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1878233002

Cr-Commit-Position: refs/heads/master@{#35424}

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

@@ -1848,10 +1848,26 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
           destination->IsRegister() ? g.ToRegister(destination) : kScratchReg;
       switch (src.type()) {
         case Constant::kInt32:
-          __ mov(dst, Operand(src.ToInt32()));
+#if !V8_TARGET_ARCH_PPC64
+          if (src.rmode() == RelocInfo::WASM_MEMORY_REFERENCE) {
+            __ mov(dst, Operand(src.ToInt32(), src.rmode()));
+          } else {
+#endif
+            __ mov(dst, Operand(src.ToInt32()));
+#if !V8_TARGET_ARCH_PPC64
+          }
+#endif
           break;
         case Constant::kInt64:
-          __ mov(dst, Operand(src.ToInt64()));
+#if V8_TARGET_ARCH_PPC64
+          if (src.rmode() == RelocInfo::WASM_MEMORY_REFERENCE) {
+            __ mov(dst, Operand(src.ToInt64(), src.rmode()));
+          } else {
+#endif
+            __ mov(dst, Operand(src.ToInt64()));
+#if V8_TARGET_ARCH_PPC64
+          }
+#endif
           break;
         case Constant::kFloat32:
           __ Move(dst,