auto merge of #8855 : michaelwoerister/rust/captured_vars, r=jdm

This pull request includes
* support for variables captured in closures*,
* a fix for issue #8512: arguments of non-immediate type (structs, tuples, etc) passed by value can now be accessed correctly in GDB. (I managed to fix this by using `llvm::DIBuilder::createComplexVariable()`. ~~However, I am not sure if this relies on unstable implementation details of LLVM's debug info handling. I'll try to clarify this on the LLVM mailing list~~).
* simplification of the `debuginfo` module's public interface: the caller of functions like `create_local_var_metadata()` doesn't have to know and catch all cases when it mustn't call the function,
* a cleanup refactoring with unified handling for locals, [self] arguments, captured variables, and match bindings,
* and proper span information for self arguments.

\* However, see comment at https://github.com/michaelwoerister/rust/blob/1d916ace136a27e354d73d65f488603c65f65bd2/src/test/debug-info/var-captured-in-nested-closure.rs#L62 . This is the same problem as with the fix for issue #8512 above: We are probably using `llvm.dbg.declare` in an unsupported way that works today but might not work after the next LLVM update.

Cheers,
Michael

Fixes #8512
Fixes #1341

Author: bors

src/librustc/lib/llvm.rs

@@ -2084,6 +2084,31 @@ pub mod llvm {
                                                         ColumnNo: c_uint)
                                                         -> ValueRef;
 
+        #[fast_ffi]
+        pub fn LLVMDIBuilderCreateOpDeref(IntType: TypeRef) -> ValueRef;
+
+        #[fast_ffi]
+        pub fn LLVMDIBuilderCreateOpPlus(IntType: TypeRef) -> ValueRef;
+
+        #[fast_ffi]
+        pub fn LLVMDIBuilderCreateComplexVariable(Builder: DIBuilderRef,
+            Tag: c_uint,
+            Scope: ValueRef,
+            Name: *c_char,
+            File: ValueRef,
+            LineNo: c_uint,
+            Ty: ValueRef,
+            AddrOps: *ValueRef,
+            AddrOpsCount: c_uint,
+            ArgNo: c_uint)
+            -> ValueRef;
+
+        #[fast_ffi]
+        pub fn LLVMIsAArgument(value_ref: ValueRef) -> ValueRef;
+
+        #[fast_ffi]
+        pub fn LLVMIsAAllocaInst(value_ref: ValueRef) -> ValueRef;
+
         pub fn LLVMInitializeX86TargetInfo();
         pub fn LLVMInitializeX86Target();
         pub fn LLVMInitializeX86TargetMC();

src/librustc/middle/moves.rs

@@ -143,7 +143,7 @@ use syntax::visit;
 use syntax::visit::Visitor;
 use syntax::codemap::Span;
 
-#[deriving(Encodable, Decodable)]
+#[deriving(Eq, Encodable, Decodable)]
 pub enum CaptureMode {
     CapCopy, // Copy the value into the closure.
     CapMove, // Move the value into the closure.

src/librustc/middle/trans/_match.rs

@@ -2000,19 +2000,20 @@ pub fn store_arg(mut bcx: @mut Block,
     let arg_ty = node_id_type(bcx, pat.id);
     add_clean(bcx, llval, arg_ty);
 
-    match simple_identifier(pat) {
-        Some(_) => {
-            // Optimized path for `x: T` case. This just adopts
-            // `llval` wholesale as the pointer for `x`, avoiding the
-            // general logic which may copy out of `llval`.
-            bcx.fcx.llargs.insert(pat.id, llval);
-        }
-
-        None => {
-            // General path. Copy out the values that are used in the
-            // pattern.
-            bcx = bind_irrefutable_pat(bcx, pat, llval, BindArgument);
-        }
+    // Debug information (the llvm.dbg.declare intrinsic to be precise) always expects to get an
+    // alloca, which only is the case on the general path, so lets disable the optimized path when
+    // debug info is enabled.
+    let fast_path = !bcx.ccx().sess.opts.extra_debuginfo && simple_identifier(pat).is_some();
+
+    if fast_path {
+        // Optimized path for `x: T` case. This just adopts
+        // `llval` wholesale as the pointer for `x`, avoiding the
+        // general logic which may copy out of `llval`.
+        bcx.fcx.llargs.insert(pat.id, llval);
+    } else {
+        // General path. Copy out the values that are used in the
+        // pattern.
+        bcx = bind_irrefutable_pat(bcx, pat, llval, BindArgument);
     }
 
     return bcx;

src/librustc/middle/trans/base.rs

@@ -131,20 +131,6 @@ pub fn push_ctxt(s: &'static str) -> _InsnCtxt {
     _InsnCtxt { _x: () }
 }
 
-fn fcx_has_nonzero_span(fcx: &FunctionContext) -> bool {
-    match fcx.span {
-        None => false,
-        Some(span) => *span.lo != 0 || *span.hi != 0
-    }
-}
-
-fn span_is_empty(opt_span: &Option<Span>) -> bool {
-    match *opt_span {
-        None => true,
-        Some(span) => *span.lo == 0 && *span.hi == 0
-    }
-}
-
 struct StatRecorder<'self> {
     ccx: @mut CrateContext,
     name: &'self str,
@@ -1132,8 +1118,7 @@ pub fn trans_stmt(cx: @mut Block, s: &ast::Stmt) -> @mut Block {
             match d.node {
                 ast::DeclLocal(ref local) => {
                     bcx = init_local(bcx, *local);
-                    if cx.sess().opts.extra_debuginfo
-                        && fcx_has_nonzero_span(bcx.fcx) {
+                    if cx.sess().opts.extra_debuginfo {
                         debuginfo::create_local_var_metadata(bcx, *local);
                     }
                 }
@@ -1633,12 +1618,7 @@ pub fn new_fn_ctxt_w_id(ccx: @mut CrateContext,
         }
     };
     let uses_outptr = type_of::return_uses_outptr(ccx.tcx, substd_output_type);
-
-    let debug_context = if id != -1 && ccx.sess.opts.debuginfo && !span_is_empty(&sp) {
-        Some(debuginfo::create_function_debug_context(ccx, id, param_substs, llfndecl))
-    } else {
-        None
-    };
+    let debug_context = debuginfo::create_function_debug_context(ccx, id, param_substs, llfndecl);
 
     let fcx = @mut FunctionContext {
           llfn: llfndecl,
@@ -1784,7 +1764,7 @@ pub fn copy_args_to_allocas(fcx: @mut FunctionContext,
             fcx.llself = Some(ValSelfData {v: self_val, ..slf});
             add_clean(bcx, self_val, slf.t);
 
-            if fcx.ccx.sess.opts.extra_debuginfo && fcx_has_nonzero_span(fcx) {
+            if fcx.ccx.sess.opts.extra_debuginfo {
                 debuginfo::create_self_argument_metadata(bcx, slf.t, self_val);
             }
         }
@@ -1811,7 +1791,7 @@ pub fn copy_args_to_allocas(fcx: @mut FunctionContext,
         };
         bcx = _match::store_arg(bcx, args[arg_n].pat, llarg);
 
-        if fcx.ccx.sess.opts.extra_debuginfo && fcx_has_nonzero_span(fcx) {
+        if fcx.ccx.sess.opts.extra_debuginfo {
             debuginfo::create_argument_metadata(bcx, &args[arg_n]);
         }
     }

src/librustc/middle/trans/closure.rs

@@ -17,6 +17,7 @@ use middle::trans::base::*;
 use middle::trans::build::*;
 use middle::trans::common::*;
 use middle::trans::datum::{Datum, INIT};
+use middle::trans::debuginfo;
 use middle::trans::expr;
 use middle::trans::glue;
 use middle::trans::type_of::*;
@@ -307,7 +308,17 @@ pub fn load_environment(fcx: @mut FunctionContext,
     // Load a pointer to the closure data, skipping over the box header:
     let llcdata = opaque_box_body(bcx, cdata_ty, fcx.llenv);
 
-    // Populate the upvars from the environment.
+    // Store the pointer to closure data in an alloca for debug info because that's what the
+    // llvm.dbg.declare intrinsic expects
+    let env_pointer_alloca = if fcx.ccx.sess.opts.extra_debuginfo {
+        let alloc = alloc_ty(bcx, ty::mk_mut_ptr(bcx.tcx(), cdata_ty), "__debuginfo_env_ptr");
+        Store(bcx, llcdata, alloc);
+        Some(alloc)
+    } else {
+        None
+    };
+
+    // Populate the upvars from the environment
     let mut i = 0u;
     for cap_var in cap_vars.iter() {
         let mut upvarptr = GEPi(bcx, llcdata, [0u, i]);
@@ -317,6 +328,18 @@ pub fn load_environment(fcx: @mut FunctionContext,
         }
         let def_id = ast_util::def_id_of_def(cap_var.def);
         fcx.llupvars.insert(def_id.node, upvarptr);
+
+        for &env_pointer_alloca in env_pointer_alloca.iter() {
+            debuginfo::create_captured_var_metadata(
+                bcx,
+                def_id.node,
+                cdata_ty,
+                env_pointer_alloca,
+                i,
+                sigil,
+                cap_var.span);
+        }
+
         i += 1u;
     }
 }

src/librustc/middle/trans/common.rs

@@ -228,7 +228,7 @@ pub struct FunctionContext {
     ccx: @mut CrateContext,
 
     // Used and maintained by the debuginfo module.
-    debug_context: Option<~debuginfo::FunctionDebugContext>
+    debug_context: debuginfo::FunctionDebugContext,
 }
 
 impl FunctionContext {

src/librustc/middle/trans/context.rs

@@ -111,7 +111,7 @@ pub struct CrateContext {
      // decl_gc_metadata knows whether to link to the module metadata, which
      // is not emitted by LLVM's GC pass when no functions use GC.
      uses_gc: bool,
-     dbg_cx: Option<debuginfo::DebugContext>,
+     dbg_cx: Option<debuginfo::CrateDebugContext>,
      do_not_commit_warning_issued: bool
 }
 
@@ -161,7 +161,7 @@ impl CrateContext {
 
             let crate_map = decl_crate_map(sess, link_meta, llmod);
             let dbg_cx = if sess.opts.debuginfo {
-                Some(debuginfo::DebugContext::new(llmod, name.to_owned()))
+                Some(debuginfo::CrateDebugContext::new(llmod, name.to_owned()))
             } else {
                 None
             };