Use an object to control the blocking of the constant pool...

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
===================================================================
--- src/arm/full-codegen-arm.cc	(revision 4448)
+++ src/arm/full-codegen-arm.cc	(working copy)
@@ -194,36 +194,37 @@
       __ CallRuntime(Runtime::kTraceExit, 1);
     }
 
+#ifdef DEBUG
     // Add a label for checking the size of the code used for returning.
     Label check_exit_codesize;
     masm_->bind(&check_exit_codesize);
+#endif
 
-    // Calculate the exact length of the return sequence and make sure that
-    // the constant pool is not emitted inside of the return sequence.
-    int num_parameters = scope()->num_parameters();
-    int32_t sp_delta = (num_parameters + 1) * kPointerSize;
-    int return_sequence_length = Assembler::kJSReturnSequenceLength;
-    if (!masm_->ImmediateFitsAddrMode1Instruction(sp_delta)) {
-      // Additional mov instruction generated.
-      return_sequence_length++;
+    {
+      // Make sure that the constant pool is not emitted inside of the return
+      // sequence.
+      Assembler::BlockConstPoolScope block_const_pool(masm_);
+
+      // Here we use masm_-> instead of the __ macro to avoid the code coverage
+      // tool from instrumenting as we rely on the code size here.
+      int32_t sp_delta = (scope()->num_parameters() + 1) * kPointerSize;
+      CodeGenerator::RecordPositions(masm_, position);
+      __ RecordJSReturn();
+      masm_->mov(sp, fp);
+      masm_->ldm(ia_w, sp, fp.bit() | lr.bit());
+      masm_->add(sp, sp, Operand(sp_delta));
+      masm_->Jump(lr);
     }
-    masm_->BlockConstPoolFor(return_sequence_length);
 
-    CodeGenerator::RecordPositions(masm_, position);
-    __ RecordJSReturn();
-    __ mov(sp, fp);
-    __ ldm(ia_w, sp, fp.bit() | lr.bit());
-    __ add(sp, sp, Operand(sp_delta));
-    __ Jump(lr);
-
+#ifdef DEBUG
     // Check that the size of the code used for returning matches what is
-    // expected by the debugger. The add instruction above is an addressing
-    // mode 1 instruction where there are restrictions on which immediate values
-    // can be encoded in the instruction and which immediate values requires
-    // use of an additional instruction for moving the immediate to a temporary
-    // register.
-    ASSERT_EQ(return_sequence_length,
-              masm_->InstructionsGeneratedSince(&check_exit_codesize));
+    // expected by the debugger. If the sp_delts above cannot be encoded in the
+    // add instruction the add will generate two instructions.
+    int return_sequence_length =
+        masm_->InstructionsGeneratedSince(&check_exit_codesize);
+    CHECK(return_sequence_length == Assembler::kJSReturnSequenceLength ||
+          return_sequence_length == Assembler::kJSReturnSequenceLength + 1);
+#endif
   }
 }