[Lldb-commits] [lldb] [lldb] Add SBType::GetByteAlign (PR #90960)

[Pavel Labath via lldb-commits]

https://github.com/labath created https://github.com/llvm/llvm-project/pull/90960

lldb already mostly(*) tracks this information. This just makes it available to the SB users.

(*) It does not do that for typedefs right now see llvm.org/pr90958

>From 738c13a680b945a0aea1dc762e7122b5ce5608ad Mon Sep 17 00:00:00 2001
From: Pavel Labath <pavel at labath.sk>
Date: Fri, 3 May 2024 11:18:15 +0000
Subject: [PATCH] [lldb] Add SBType::GetByteAlign

lldb already mostly(*) tracks this information. This just makes it
available to the SB users.

(*) It does not do that for typedefs right now see llvm.org/pr90958
---
 lldb/include/lldb/API/SBType.h                |  2 ++
 lldb/source/API/SBType.cpp                    | 12 +++++++++++
 lldb/test/API/python_api/type/TestTypeList.py | 21 +++++++++++++++++++
 lldb/test/API/python_api/type/main.cpp        |  3 +++
 4 files changed, 38 insertions(+)

diff --git a/lldb/include/lldb/API/SBType.h b/lldb/include/lldb/API/SBType.h
index 5b9ff2170b2b24..63ba91082d5769 100644
--- a/lldb/include/lldb/API/SBType.h
+++ b/lldb/include/lldb/API/SBType.h
@@ -150,6 +150,8 @@ class SBType {
 
   uint64_t GetByteSize();
 
+  uint64_t GetByteAlign();
+
   bool IsPointerType();
 
   bool IsReferenceType();
diff --git a/lldb/source/API/SBType.cpp b/lldb/source/API/SBType.cpp
index 6cecb5c9ea810b..f9a2a0548ef83a 100644
--- a/lldb/source/API/SBType.cpp
+++ b/lldb/source/API/SBType.cpp
@@ -25,6 +25,7 @@
 #include "lldb/Utility/Stream.h"
 
 #include "llvm/ADT/APSInt.h"
+#include "llvm/Support/MathExtras.h"
 
 #include <memory>
 #include <optional>
@@ -132,6 +133,17 @@ uint64_t SBType::GetByteSize() {
   return 0;
 }
 
+uint64_t SBType::GetByteAlign() {
+  LLDB_INSTRUMENT_VA(this);
+
+  if (!IsValid()) return 0;
+
+  std::optional<uint64_t> bit_align =
+      m_opaque_sp->GetCompilerType(/*prefer_dynamic=*/false)
+          .GetTypeBitAlign(nullptr);
+  return llvm::divideCeil(bit_align.value_or(0), 8);
+}
+
 bool SBType::IsPointerType() {
   LLDB_INSTRUMENT_VA(this);
 
diff --git a/lldb/test/API/python_api/type/TestTypeList.py b/lldb/test/API/python_api/type/TestTypeList.py
index 17e27b624511cf..0498396903dcbd 100644
--- a/lldb/test/API/python_api/type/TestTypeList.py
+++ b/lldb/test/API/python_api/type/TestTypeList.py
@@ -272,3 +272,24 @@ def test(self):
             self.assertTrue(int_enum_uchar)
             self.DebugSBType(int_enum_uchar)
             self.assertEqual(int_enum_uchar.GetName(), "unsigned char")
+
+    def test_GetByteAlign(self):
+        """Exercise SBType::GetByteAlign"""
+        self.build()
+        spec = lldb.SBModuleSpec()
+        spec.SetFileSpec(lldb.SBFileSpec(self.getBuildArtifact()))
+        module = lldb.SBModule(spec)
+        self.assertTrue(module)
+
+        # Invalid types should not crash.
+        self.assertEqual(lldb.SBType().GetByteAlign(), 0)
+
+        # Try a type with natural alignment.
+        void_ptr = module.GetBasicType(lldb.eBasicTypeVoid).GetPointerType()
+        self.assertTrue(void_ptr)
+        # Not exactly guaranteed by the spec, but should be true everywhere we
+        # care about.
+        self.assertEqual(void_ptr.GetByteSize(), void_ptr.GetByteAlign())
+
+        # And an over-aligned type.
+        self.assertEqual(module.FindFirstType("OverAlignedStruct").GetByteAlign(), 128)
diff --git a/lldb/test/API/python_api/type/main.cpp b/lldb/test/API/python_api/type/main.cpp
index 7384a3d8da16fb..986ed3009a15f6 100644
--- a/lldb/test/API/python_api/type/main.cpp
+++ b/lldb/test/API/python_api/type/main.cpp
@@ -50,6 +50,9 @@ enum EnumType {};
 enum class ScopedEnumType {};
 enum class EnumUChar : unsigned char {};
 
+struct alignas(128) OverAlignedStruct {};
+OverAlignedStruct over_aligned_struct;
+
 int main (int argc, char const *argv[])
 {
     Task *task_head = new Task(-1, NULL);