[lldb] Fix GetExpressionPath for vector registers

[da-viper]

Vector registers have synthetic values for display purposes. This causes SBValue::GetExpressionPath to dispatch
to ValueObjectSynthetic instead of ValueObjectRegister, producing incorrect results.

Fixes #147144

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Ebuka Ezike (da-viper)

Changes

Vector registers have synthetic values for display purposes. This causes SBValue::GetExpressionPath to dispatch
to ValueObjectSynthetic instead of ValueObjectRegister, producing incorrect results.

Fixes #147144

---

Full diff: https://github.com/llvm/llvm-project/pull/169210.diff

5 Files Affected:

• (modified) lldb/include/lldb/ValueObject/ValueObjectSynthetic.h (+5)
• (modified) lldb/source/ValueObject/ValueObjectSynthetic.cpp (+12)
• (added) lldb/test/API/python_api/exprpath_register/Makefile (+3)
• (added) lldb/test/API/python_api/exprpath_register/TestExprPathRegisters.py (+64)
• (added) lldb/test/API/python_api/exprpath_register/main.c (+10)

diff --git a/lldb/include/lldb/ValueObject/ValueObjectSynthetic.h b/lldb/include/lldb/ValueObject/ValueObjectSynthetic.h
index 063d796ee4eec..1a82fd78bbba3 100644
--- a/lldb/include/lldb/ValueObject/ValueObjectSynthetic.h
+++ b/lldb/include/lldb/ValueObject/ValueObjectSynthetic.h
@@ -123,6 +123,11 @@ class ValueObjectSynthetic : public ValueObject {
 
   void SetLanguageFlags(uint64_t flags) override;
 
+  void
+  GetExpressionPath(Stream &stream,
+                    GetExpressionPathFormat epformat =
+                        eGetExpressionPathFormatDereferencePointers) override;
+
 protected:
   bool UpdateValue() override;
 
diff --git a/lldb/source/ValueObject/ValueObjectSynthetic.cpp b/lldb/source/ValueObject/ValueObjectSynthetic.cpp
index f673c51a88412..1b689257224df 100644
--- a/lldb/source/ValueObject/ValueObjectSynthetic.cpp
+++ b/lldb/source/ValueObject/ValueObjectSynthetic.cpp
@@ -443,3 +443,15 @@ void ValueObjectSynthetic::SetLanguageFlags(uint64_t flags) {
   else
     this->ValueObject::SetLanguageFlags(flags);
 }
+
+void ValueObjectSynthetic::GetExpressionPath(Stream &stream,
+                                             GetExpressionPathFormat epformat) {
+  if (const lldb::ValueType obj_value_type = GetValueType();
+      IsSynthetic() && (obj_value_type == lldb::eValueTypeRegister ||
+                        obj_value_type == lldb::eValueTypeRegisterSet)) {
+
+    if (const lldb::ValueObjectSP raw_value = GetNonSyntheticValue())
+      return raw_value->GetExpressionPath(stream, epformat);
+  }
+  return ValueObject::GetExpressionPath(stream, epformat);
+}
diff --git a/lldb/test/API/python_api/exprpath_register/Makefile b/lldb/test/API/python_api/exprpath_register/Makefile
new file mode 100644
index 0000000000000..10495940055b6
--- /dev/null
+++ b/lldb/test/API/python_api/exprpath_register/Makefile
@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules
diff --git a/lldb/test/API/python_api/exprpath_register/TestExprPathRegisters.py b/lldb/test/API/python_api/exprpath_register/TestExprPathRegisters.py
new file mode 100644
index 0000000000000..4ffbc5e49fb0d
--- /dev/null
+++ b/lldb/test/API/python_api/exprpath_register/TestExprPathRegisters.py
@@ -0,0 +1,64 @@
+"""
+Test Getting the expression path for registers works correctly
+"""
+
+import lldb
+from lldbsuite.test import lldbutil
+from lldbsuite.test.lldbtest import TestBase, VALID_BREAKPOINT, VALID_TARGET
+
+
+class TestExprPathRegisters(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def verify_register_path(self, reg_value: lldb.SBValue):
+        stream = lldb.SBStream()
+        reg_name = reg_value.name
+        self.assertTrue(
+            reg_value.GetExpressionPath(stream),
+            f"Expected an expression path for register {reg_name}.",
+        )
+        reg_expr_path = stream.GetData()
+        self.assertEqual(reg_expr_path, f"${reg_name}")
+
+    def test_float_registers(self):
+        """Verify the expression path of the registers is valid."""
+        self.build()
+        _, _, thread, _ = lldbutil.run_to_name_breakpoint(self, "my_foo")
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame, "Expected a valid Frame.")
+
+        # possible floating point register on some cpus.
+        register_names = [
+            "xmm0",
+            "ymm0",
+            "v0",
+            "v1",
+            "f0",
+            "f1",
+            "d0",
+            "d1",
+            "vr0",
+            "vr1",
+            "st0",
+            "st1",
+        ]
+        for name in register_names:
+            reg_value = frame.FindRegister(name)
+            # some the register will not be available for the cpu
+            # only verify if it is valid.
+            if reg_value:
+                self.verify_register_path(reg_value)
+
+    def test_all_registers(self):
+        """Test all the registers that is avaiable on the machine"""
+        self.build()
+        _, _, thread, _ = lldbutil.run_to_name_breakpoint(self, "my_foo")
+        frame = thread.GetSelectedFrame()
+        self.assertTrue(frame, "Expected a valid Frame.")
+
+        register_sets = frame.GetRegisters()
+        self.assertTrue(register_sets.IsValid(), "Expected Frame Registers")
+
+        for register_set in register_sets:
+            for register in register_set.children:
+                self.verify_register_path(register)
diff --git a/lldb/test/API/python_api/exprpath_register/main.c b/lldb/test/API/python_api/exprpath_register/main.c
new file mode 100644
index 0000000000000..4809a87cdf210
--- /dev/null
+++ b/lldb/test/API/python_api/exprpath_register/main.c
@@ -0,0 +1,10 @@
+
+float my_foo() {
+  float result = 10.0 + 20.0;
+  return result;
+}
+
+int main(void) {
+  float result = my_foo();
+  return (int)result;
+}