PPC: Check if rb is valid when creating MemOperand

r0 is used to indicate a value of "0" in which case
only the ra() value gets used.

Change-Id: I5ea5c51c1a652d042137c2d940818b93dac52492
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3159668Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76830}

src/codegen/ppc/macro-assembler-ppc.cc

@@ -3231,7 +3231,10 @@ void TurboAssembler::StoreSimd128(Simd128Register src, const MemOperand& mem) {
 #define GenerateMemoryLEOperation(reg, mem, op)                \
   {                                                            \
     if (mem.offset() == 0) {                                   \
-      op(reg, mem);                                            \
+      if (mem.rb() != no_reg)                                  \
+        op(reg, mem);                                          \
+      else                                                     \
+        op(reg, MemOperand(r0, mem.ra()));                     \
     } else if (is_int16(mem.offset())) {                       \
       if (mem.rb() != no_reg)                                  \
         addi(scratch, mem.rb(), Operand(mem.offset()));        \