Allow runtimes to execute custom LLVM ModulePasses over the expression IR

During expression evaluation, the ClangExpressionParser preforms a
number of hard-coded fixups on the expression's IR before the module
is assembled and dispatched to be run in a ThreadPlan.

This patch allows the runtimes to register LLVM passes to be run over the
generated IR, that they may perform language or architecture-specfic fixups
or analyses over the generated expression.

This makes expression evaluation for plugins more flexible and allows
language-specific fixes to reside in their own module, rather than
littering the expression evaluator itself with language-specific fixes.

llvm-svn: 272800

lldb/include/lldb/Expression/LLVMUserExpression.h

@@ -16,6 +16,9 @@
 #include <map>
 #include <vector>
 
+// Other libraries and framework includes
+#include "llvm/IR/LegacyPassManager.h"
+
 // Project includes
 #include "lldb/Expression/UserExpression.h"
 
@@ -35,6 +38,17 @@ namespace lldb_private
 class LLVMUserExpression : public UserExpression
 {
 public:
+    // The IRPasses struct is filled in by a runtime after an expression is compiled and can be used to to run
+    // fixups/analysis passes as required. EarlyPasses are run on the generated module before lldb runs its own IR
+    // fixups and inserts instrumentation code/pointer checks. LatePasses are run after the module has been processed by
+    // llvm, before the module is assembled and run in the ThreadPlan.
+    struct IRPasses
+    {
+        IRPasses() : EarlyPasses(nullptr), LatePasses(nullptr){};
+        std::shared_ptr<llvm::legacy::PassManager> EarlyPasses;
+        std::shared_ptr<llvm::legacy::PassManager> LatePasses;
+    };
+
     LLVMUserExpression(ExecutionContextScope &exe_scope, const char *expr, const char *expr_prefix,
                        lldb::LanguageType language, ResultType desired_type,
                        const EvaluateExpressionOptions &options);

lldb/include/lldb/Target/LanguageRuntime.h

@@ -22,6 +22,8 @@
 #include "lldb/Core/ValueObject.h"
 #include "lldb/Core/Value.h"
 #include "lldb/Target/ExecutionContextScope.h"
+#include "lldb/Expression/LLVMUserExpression.h"
+
 #include "clang/Basic/TargetOptions.h"
 
 namespace lldb_private {
@@ -157,6 +159,13 @@ public:
         return false;
     }
 
+    // Called by ClangExpressionParser::PrepareForExecution to query for any custom LLVM IR passes
+    // that need to be run before an expression is assembled and run.
+    virtual bool
+    GetIRPasses(LLVMUserExpression::IRPasses &custom_passes)
+    {
+        return false;
+    }
 protected:
     //------------------------------------------------------------------
     // Classes that inherit from LanguageRuntime can see and modify these

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -837,6 +837,30 @@ ClangExpressionParser::PrepareForExecution (lldb::addr_t &func_addr,
         sc.target_sp = target_sp;
     }
 
+    LLVMUserExpression::IRPasses custom_passes;
+    {
+        auto lang = m_expr.Language();
+        if (log)
+            log->Printf("%s - Currrent expression language is %s\n", __FUNCTION__,
+                        Language::GetNameForLanguageType(lang));
+
+        if (lang != lldb::eLanguageTypeUnknown)
+        {
+            auto runtime = exe_ctx.GetProcessSP()->GetLanguageRuntime(lang);
+            if (runtime)
+                runtime->GetIRPasses(custom_passes);
+        }
+    }
+
+    if (custom_passes.EarlyPasses)
+    {
+        if (log)
+            log->Printf("%s - Running Early IR Passes from LanguageRuntime on expression module '%s'", __FUNCTION__,
+                        m_expr.FunctionName());
+
+        custom_passes.EarlyPasses->run(*llvm_module_ap);
+    }
+
     execution_unit_sp.reset(new IRExecutionUnit (m_llvm_context, // handed off here
                                                  llvm_module_ap, // handed off here
                                                  function_name,
@@ -925,12 +949,22 @@ ClangExpressionParser::PrepareForExecution (lldb::addr_t &func_addr,
 
                 IRDynamicChecks ir_dynamic_checks(*process->GetDynamicCheckers(), function_name.AsCString());
 
-                if (!ir_dynamic_checks.runOnModule(*execution_unit_sp->GetModule()))
+                llvm::Module *module = execution_unit_sp->GetModule();
+                if (!module || !ir_dynamic_checks.runOnModule(*module))
                 {
                     err.SetErrorToGenericError();
                     err.SetErrorString("Couldn't add dynamic checks to the expression");
                     return err;
                 }
+
+                if (custom_passes.LatePasses)
+                {
+                    if (log)
+                        log->Printf("%s - Running Late IR Passes from LanguageRuntime on expression module '%s'",
+                                    __FUNCTION__, m_expr.FunctionName());
+
+                    custom_passes.LatePasses->run(*module);
+                }
             }
         }