[compiler] Fix some -Wshadow warnings

Bug: v8:12244,v8:12245
Change-Id: I066f182f924d634a489b626e899c502f837fe395
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3213139Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77363}

src/compiler/backend/code-generator.cc

@@ -1213,10 +1213,10 @@ DeoptimizationExit* CodeGenerator::BuildTranslation(
   }
   if (immediate_args_count != 0) {
     auto immediate_args = zone()->New<ZoneVector<ImmediateOperand*>>(zone());
-    InstructionOperandIterator iter(
+    InstructionOperandIterator imm_iter(
         instr, frame_state_offset - immediate_args_count - 1);
     for (size_t i = 0; i < immediate_args_count; i++) {
-      immediate_args->emplace_back(ImmediateOperand::cast(iter.Advance()));
+      immediate_args->emplace_back(ImmediateOperand::cast(imm_iter.Advance()));
     }
     exit->set_immediate_args(immediate_args);
   }

src/compiler/backend/instruction.cc

@@ -1182,10 +1182,10 @@ std::ostream& operator<<(std::ostream& os, const InstructionSequence& code) {
     Constant constant = code.immediates_[i];
     os << "IMM#" << i << ": " << constant << "\n";
   }
-  int i = 0;
+  int n = 0;
   for (ConstantMap::const_iterator it = code.constants_.begin();
-       it != code.constants_.end(); ++i, ++it) {
-    os << "CST#" << i << ": v" << it->first << " = " << it->second << "\n";
+       it != code.constants_.end(); ++n, ++it) {
+    os << "CST#" << n << ": v" << it->first << " = " << it->second << "\n";
   }
   for (int i = 0; i < code.InstructionBlockCount(); i++) {
     auto* block = code.InstructionBlockAt(RpoNumber::FromInt(i));

src/compiler/backend/jump-threading.cc

@@ -70,8 +70,8 @@ bool JumpThreading::ComputeForwarding(Zone* local_zone,
   int32_t empty_no_deconstruct_frame_return_size;
 
   // Iterate over the blocks forward, pushing the blocks onto the stack.
-  for (auto const block : code->instruction_blocks()) {
-    RpoNumber current = block->rpo_number();
+  for (auto const instruction_block : code->instruction_blocks()) {
+    RpoNumber current = instruction_block->rpo_number();
     state.PushIfUnvisited(current);
 
     // Process the stack, which implements DFS through empty blocks.