MIPS32: Improve string and class loads

Tested:
- MIPS32 Android boots in QEMU
- test-art-host-gtest
- test-art-target-run-test-optimizing in QEMU, on CI20
- test-art-target-gtest on CI20

Change-Id: I70fd5d5267f8594c3b29d5a4ccf66b8ca8b09df3
diff --git a/compiler/utils/mips/assembler_mips.cc b/compiler/utils/mips/assembler_mips.cc
index ebaf1c0..608b3bc 100644
--- a/compiler/utils/mips/assembler_mips.cc
+++ b/compiler/utils/mips/assembler_mips.cc
@@ -2024,6 +2024,10 @@
   Bind(&pc_rel_base_label_);
 }
 
+uint32_t MipsAssembler::GetPcRelBaseLabelLocation() const {
+  return GetLabelLocation(&pc_rel_base_label_);
+}
+
 void MipsAssembler::FinalizeLabeledBranch(MipsLabel* label) {
   uint32_t length = branches_.back().GetLength();
   if (!label->IsBound()) {