From 0f98cb41988d1fdd0cb33fb274253cba3bde5cfa Mon Sep 17 00:00:00 2001
From: Michael Woerister <michaelwoerister@gmail>
Date: Tue, 17 Dec 2013 16:52:16 +0100
Subject: [PATCH] debuginfo: Properly support by-value self arguments
---
src/librustc/middle/trans/debuginfo.rs | 27 ++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/src/librustc/middle/trans/debuginfo.rs b/src/librustc/middle/trans/debuginfo.rs
index 0783d5b418f..a77e8f764f3 100644
--- a/src/librustc/middle/trans/debuginfo.rs
+++ b/src/librustc/middle/trans/debuginfo.rs
@@ -129,11 +129,13 @@ use driver::session;
use lib::llvm::llvm;
use lib::llvm::{ModuleRef, ContextRef, ValueRef};
use lib::llvm::debuginfo::*;
+use middle::trans::adt;
+use middle::trans::base;
+use middle::trans::build;
use middle::trans::common::*;
use middle::trans::machine;
use middle::trans::type_of;
use middle::trans::type_::Type;
-use middle::trans::adt;
use middle::trans;
use middle::ty;
use middle::pat_util;
@@ -453,12 +455,29 @@ pub fn create_self_argument_metadata(bcx: @mut Block,
let address_operations = &[unsafe { llvm::LLVMDIBuilderCreateOpDeref(Type::i64().to_ref()) }];
+ // The self argument comes in one of two forms:
+ // (1) For `&self`, `~self`, and `@self` it is an alloca containing a pointer to the data. That
+ // is the `{&~@}self` pointer is contained by value in the alloca, and `type_of_self` will
+ // be `{&~@}Self`
+ // (2) For by-value `self`, `llptr` will not be an alloca, but a pointer to the self-value. That
+ // is by-value `self` is always implicitly passed by reference (sic!). So we have a couple
+ // of problems here:
+ // (a) There is no alloca to give to `llvm.dbg.declare` and
+ // (b) `type_of_self` is `Self`, but `llptr` is of type `*Self`
+ // In order to solve this problem, the else branch below creates a helper alloca which
+ // contains a copy of `llptr`. We then describe the `self` parameter by pointing
+ // `llvm.dbg.declare` to this helper alloca and tell it that the pointer there needs to be
+ // dereferenced once to get to the actual data (similar to non-immediate by-value args).
let variable_access = if unsafe { llvm::LLVMIsAAllocaInst(llptr) } != ptr::null() {
DirectVariable { alloca: llptr }
} else {
- // This is not stable and may break with future LLVM versions. llptr should really always
- // be an alloca. Anything else is not supported and just works by chance.
- IndirectVariable { alloca: llptr, address_operations: address_operations }
+ // Create a helper alloca that allows us to track the self-argument properly. The alloca
+ // contains a pointer to the self-value.
+ let ptr_type = ty::mk_mut_ptr(bcx.tcx(), type_of_self);
+ let helper_alloca = base::alloc_ty(bcx, ptr_type, "__self");
+ build::Store(bcx, llptr, helper_alloca);
+
+ IndirectVariable { alloca: helper_alloca, address_operations: address_operations }
};
declare_local(bcx,