[lldb] Read the precise SDK for the current CU first.

This fixes an oversight made during the switch to precise compiler
invocations.

rdar://141013288

Author: adrian-prantl

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -2148,7 +2148,7 @@ static std::string GetSDKPathFromDebugInfo(std::string m_description,
     return {};
   auto sdk_or_err = platform_sp->GetSDKPathFromDebugInfo(module);
   if (!sdk_or_err) {
-    Debugger::ReportError("Error while parsing SDK path from debug-info: " +
+    Debugger::ReportError("Error while parsing SDK path from debug info: " +
                           toString(sdk_or_err.takeError()));
     return {};
   }
@@ -2825,9 +2825,29 @@ SwiftASTContext::CreateInstance(const SymbolContext &sc,
   FileSpec target_sdk_spec = target_sp ? target_sp->GetSDKPath() : FileSpec();
   if (target_sdk_spec && FileSystem::Instance().Exists(target_sdk_spec)) {
     swift_ast_sp->SetPlatformSDKPath(target_sdk_spec.GetPath());
+    LOG_PRINTF(GetLog(LLDBLog::Types), "Using target SDK override: %s",
+               target_sdk_spec.GetPath().c_str());
     handled_sdk_path = true;
   }
 
+  // Get the precise SDK from the symbol context.
+  if (cu)
+    if (auto platform_sp = Platform::GetHostPlatform()) {
+      auto sdk_or_err = platform_sp->GetSDKPathFromDebugInfo(*cu);
+      if (!sdk_or_err)
+        Debugger::ReportError("Error while parsing SDK path from debug info: " +
+                              toString(sdk_or_err.takeError()));
+      else {
+        std::string sdk_path = GetSDKPath(m_description, *sdk_or_err);
+        if (!sdk_path.empty()) {
+          swift_ast_sp->SetPlatformSDKPath(sdk_path);
+          handled_sdk_path = true;
+          LOG_PRINTF(GetLog(LLDBLog::Types), "Using precise SDK: %s",
+                     sdk_path.c_str());
+        }
+      }
+    }
+
   if (!handled_sdk_path) {
     for (size_t mi = 0; mi != num_images; ++mi) {
       ModuleSP module_sp = modules.GetModuleAtIndex(mi);
@@ -2839,8 +2859,8 @@ SwiftASTContext::CreateInstance(const SymbolContext &sc,
       if (sdk_path.empty())
         continue;
 
-      handled_sdk_path = true;
       swift_ast_sp->SetPlatformSDKPath(sdk_path);
+      handled_sdk_path = true;
       break;
     }
   }

lldb/test/API/lang/swift/xcode_sdk/TestSwiftXcodeSDK.py

@@ -10,16 +10,26 @@ class TestSwiftXcodeSDK(lldbtest.TestBase):
     mydir = lldbtest.TestBase.compute_mydir(__file__)
     NO_DEBUG_INFO_TESTCASE = True
 
-    def check_log(self, log, expected_path):
+    def check_log(self, log, expected_path, expect_precise):
         import io
         logfile = io.open(log, "r", encoding='utf-8')
-        in_expr_log = 0
         found = 0
+        precise = False
         for line in logfile:
-            if (line.startswith(' SwiftASTContextForExpressions(module: "a", cu: "main.swift")::LogConfiguration()') and
-                "SDK path" in line and expected_path in line):
+            if not line.startswith(' SwiftASTContextForExpressions(module: "a", cu: "main.swift")'):
+                continue
+            if "Using precise SDK" in line:
+                precise = True
+                continue
+            if "Override target.sdk-path" in line:
+                precise = False
+                continue
+            if not '::LogConfiguration()' in line:
+                continue
+            if "SDK path" in line and expected_path in line:
                 found += 1
         self.assertEqual(found, 1)
+        self.assertEqual(precise, expect_precise)
 
     @swiftTest
     @skipUnlessDarwin
@@ -33,7 +43,7 @@ def test_decode(self):
         lldbutil.run_to_name_breakpoint(self, 'main')
 
         self.expect("expression 1")
-        self.check_log(log, "MacOSX")
+        self.check_log(log, "MacOSX", True)
 
     @swiftTest
     @skipUnlessDarwin
@@ -52,7 +62,7 @@ def test_decode_sim(self):
         lldbutil.run_to_name_breakpoint(self, 'main')
 
         self.expect("expression 1")
-        self.check_log(log, "iPhoneSimulator")
+        self.check_log(log, "iPhoneSimulator", True)
 
     @swiftTest
     @skipUnlessDarwin
@@ -72,4 +82,4 @@ def test_override(self):
         lldbutil.run_to_name_breakpoint(self, 'main')
 
         self.expect("expression 1")
-        self.check_log(log, ios_sdk)
+        self.check_log(log, ios_sdk, False)