[Lldb-commits] [lldb] [lldb] Add a return opcode to the formatter bytecode (PR #121602)

[Adrian Prantl via lldb-commits]

https://github.com/adrian-prantl created https://github.com/llvm/llvm-project/pull/121602

In LLVM we love our early exists and this opcode allows for simpler code generation.

>From bffb3f827b2e2918cd6858728efbfefd319ae2dc Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl at apple.com>
Date: Fri, 3 Jan 2025 12:51:15 -0800
Subject: [PATCH] [lldb] Add a return opcode to the formatter bytecode

In LLVM we love our early exists and this opcode allows for simpler
code generation.
---
 lldb/docs/resources/formatterbytecode.rst              |  1 +
 lldb/examples/python/formatter_bytecode.py             |  4 ++++
 lldb/source/DataFormatters/FormatterBytecode.cpp       |  3 +++
 lldb/source/DataFormatters/FormatterBytecode.def       |  1 +
 lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp | 10 ++++++++++
 5 files changed, 19 insertions(+)

diff --git a/lldb/docs/resources/formatterbytecode.rst b/lldb/docs/resources/formatterbytecode.rst
index 20e148363ef957..34fb0f7ee924c4 100644
--- a/lldb/docs/resources/formatterbytecode.rst
+++ b/lldb/docs/resources/formatterbytecode.rst
@@ -75,6 +75,7 @@ These manipulate the control stack and program counter. Both `if` and `ifelse` e
  0x12      `ifelse`    `(UInt -> )` pop two blocks from the control stack, if
                        the top of the data stack is nonzero, execute the first,
                        otherwise the second.
+ 0x13      `return`    pop the entire control stack and return
 ========  ==========  ============================================================
 
 Literals for basic types
diff --git a/lldb/examples/python/formatter_bytecode.py b/lldb/examples/python/formatter_bytecode.py
index ccd0c68a75483c..36a14be283f319 100644
--- a/lldb/examples/python/formatter_bytecode.py
+++ b/lldb/examples/python/formatter_bytecode.py
@@ -35,6 +35,7 @@ def define_opcode(n, mnemonic, name):
 define_opcode(0x10, "{", "begin")
 define_opcode(0x11, "if", "if")
 define_opcode(0x12, "ifelse", "ifelse")
+define_opcode(0x13, "return", "return")
 
 define_opcode(0x20, None, "lit_uint")
 define_opcode(0x21, None, "lit_int")
@@ -342,6 +343,9 @@ def next_byte():
             else:
                 frame.append(control.pop())
                 control.pop()
+        elif b == op_return:
+            control.clear()
+            return data[-1]
 
         # Literals.
         elif b == op_lit_uint:
diff --git a/lldb/source/DataFormatters/FormatterBytecode.cpp b/lldb/source/DataFormatters/FormatterBytecode.cpp
index e49c7506781875..7f3dbe0dba37d6 100644
--- a/lldb/source/DataFormatters/FormatterBytecode.cpp
+++ b/lldb/source/DataFormatters/FormatterBytecode.cpp
@@ -304,6 +304,9 @@ llvm::Error Interpret(std::vector<ControlStackElement> &control,
       control.pop_back();
       activate_block();
       continue;
+    case op_return:
+      control.clear();
+      return pc.takeError();
 
     // Literals.
     case op_lit_uint:
diff --git a/lldb/source/DataFormatters/FormatterBytecode.def b/lldb/source/DataFormatters/FormatterBytecode.def
index c6645631fa0065..29e0bee541c73c 100644
--- a/lldb/source/DataFormatters/FormatterBytecode.def
+++ b/lldb/source/DataFormatters/FormatterBytecode.def
@@ -27,6 +27,7 @@ DEFINE_OPCODE(0x06, "rot",  rot)
 DEFINE_OPCODE(0x10, "{", begin)
 DEFINE_OPCODE(0x11, "if", if)
 DEFINE_OPCODE(0x12, "ifelse", ifelse)
+DEFINE_OPCODE(0x13, "return", return)
 
 DEFINE_OPCODE(0x20, nullptr, lit_uint)
 DEFINE_OPCODE(0x21, nullptr, lit_int)
diff --git a/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp b/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp
index 7307db650c1629..5e980c3e1913cf 100644
--- a/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp
+++ b/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp
@@ -97,6 +97,16 @@ TEST_F(FormatterBytecodeTest, ControlOps) {
                           data));
     ASSERT_EQ(data.Pop<uint64_t>(), 42u);
   }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_begin, 3, op_lit_uint, 42,
+                           op_return, op_if, op_lit_uint, 23},
+                          data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 42u);
+  }
+}
+
+TEST_F(FormatterBytecodeTest, ConversionOps) {
   {
     DataStack data(lldb::ValueObjectSP{});
     ASSERT_TRUE(Interpret({op_is_null}, data));