auto merge of #7822 : huonw/rust/cond-debug, r=graydon

As per @pcwalton's request, `debug!(..)` is only activated when the `debug` cfg is set; that is, for `RUST_LOG=some_module=4 ./some_program` to work, it needs to be compiled with `rustc --cfg debug some_program.rs`. (Although, there is the sneaky `__debug!(..)` macro that is always active, if you *really* need it.)

It functions by making `debug!` expand to `if false { __debug!(..) }` (expanding to an `if` like this is required to make sure `debug!` statements are typechecked and to avoid unused variable warnings), and adjusting trans to skip the pointless branches in `if true ...` and `if false ...`.

The conditional expansion change also required moving the inject-std-macros step into a new pass, and makes it actually insert them at the top of the crate; this means that the cfg stripping traverses over the macros and so filters out the unused ones.

This appears to takes an unoptimised build of `librustc` from 65s to 59s; and the full bootstrap from 18m41s to 18m26s on my computer (with general background use).

`./configure --enable-debug` will enable `debug!` statements in the bootstrap build.

src/librustc/driver/driver.rs

@@ -194,6 +194,10 @@ pub fn compile_rest(sess: Session,
         //   mod bar { macro_rules! baz!(() => {{}}) }
         //
         // baz! should not use this definition unless foo is enabled.
+        crate = time(time_passes, ~"std macros injection", ||
+                     syntax::ext::expand::inject_std_macros(sess.parse_sess, copy cfg,
+                                                             crate));
+
         crate = time(time_passes, ~"configuration 1", ||
                      front::config::strip_unconfigured_items(crate));
 
@@ -214,7 +218,7 @@ pub fn compile_rest(sess: Session,
     assert!(phases.from != cu_no_trans);
 
     let (llcx, llmod, link_meta) = {
-        crate = time(time_passes, ~"extra injection", ||
+        crate = time(time_passes, ~"std injection", ||
                      front::std_inject::maybe_inject_libstd_ref(sess, crate));
 
         let ast_map = time(time_passes, ~"ast indexing", ||

src/librustc/middle/trans/base.rs

@@ -1530,7 +1530,7 @@ pub fn alloca_maybe_zeroed(cx: block, ty: Type, name: &str, zero: bool) -> Value
     let _icx = push_ctxt("alloca");
     if cx.unreachable {
         unsafe {
-            return llvm::LLVMGetUndef(ty.to_ref());
+            return llvm::LLVMGetUndef(ty.ptr_to().to_ref());
         }
     }
     let initcx = base::raw_block(cx.fcx, false, cx.fcx.get_llstaticallocas());

src/librustc/middle/trans/build.rs

@@ -569,15 +569,17 @@ pub fn LoadRangeAssert(cx: block, PointerVal: ValueRef, lo: c_ulonglong,
                        hi: c_ulonglong, signed: lib::llvm::Bool) -> ValueRef {
     let value = Load(cx, PointerVal);
 
-    unsafe {
-        let t = llvm::LLVMGetElementType(llvm::LLVMTypeOf(PointerVal));
-        let min = llvm::LLVMConstInt(t, lo, signed);
-        let max = llvm::LLVMConstInt(t, hi, signed);
-
-        do [min, max].as_imm_buf |ptr, len| {
-            llvm::LLVMSetMetadata(value, lib::llvm::MD_range as c_uint,
-                                  llvm::LLVMMDNodeInContext(cx.fcx.ccx.llcx,
-                                                            ptr, len as c_uint));
+    if !cx.unreachable {
+        unsafe {
+            let t = llvm::LLVMGetElementType(llvm::LLVMTypeOf(PointerVal));
+            let min = llvm::LLVMConstInt(t, lo, signed);
+            let max = llvm::LLVMConstInt(t, hi, signed);
+
+            do [min, max].as_imm_buf |ptr, len| {
+                llvm::LLVMSetMetadata(value, lib::llvm::MD_range as c_uint,
+                                      llvm::LLVMMDNodeInContext(cx.fcx.ccx.llcx,
+                                                                ptr, len as c_uint));
+            }
         }
     }
 

src/librustc/middle/trans/controlflow.rs

@@ -63,6 +63,38 @@ pub fn trans_if(bcx: block,
     let _indenter = indenter();
 
     let _icx = push_ctxt("trans_if");
+
+    match cond.node {
+        // `if true` and `if false` can be trans'd more efficiently,
+        // by dropping branches that are known to be impossible.
+        ast::expr_lit(@ref l) => match l.node {
+            ast::lit_bool(true) => {
+                // if true { .. } [else { .. }]
+                let then_bcx_in = scope_block(bcx, thn.info(), "if_true_then");
+                let then_bcx_out = trans_block(then_bcx_in, thn, dest);
+                let then_bcx_out = trans_block_cleanups(then_bcx_out,
+                                                        block_cleanups(then_bcx_in));
+                Br(bcx, then_bcx_in.llbb);
+                return then_bcx_out;
+            }
+            ast::lit_bool(false) => {
+                match els {
+                    // if false { .. } else { .. }
+                    Some(elexpr) => {
+                        let (else_bcx_in, else_bcx_out) =
+                            trans_if_else(bcx, elexpr, dest, "if_false_else");
+                        Br(bcx, else_bcx_in.llbb);
+                        return else_bcx_out;
+                    }
+                    // if false { .. }
+                    None => return bcx,
+                }
+            }
+            _ => {}
+        },
+        _ => {}
+    }
+
     let Result {bcx, val: cond_val} =
         expr::trans_to_datum(bcx, cond).to_result();
 
@@ -80,22 +112,8 @@ pub fn trans_if(bcx: block,
     // 'else' context
     let (else_bcx_in, next_bcx) = match els {
       Some(elexpr) => {
-        let else_bcx_in = scope_block(bcx, els.info(), "else");
-        let else_bcx_out = match elexpr.node {
-          ast::expr_if(_, _, _) => {
-            let elseif_blk = ast_util::block_from_expr(elexpr);
-            trans_block(else_bcx_in, &elseif_blk, dest)
-          }
-          ast::expr_block(ref blk) => {
-            trans_block(else_bcx_in, blk, dest)
-          }
-          // would be nice to have a constraint on ifs
-          _ => bcx.tcx().sess.bug("strange alternative in if")
-        };
-        let else_bcx_out = trans_block_cleanups(else_bcx_out,
-                                                block_cleanups(else_bcx_in));
-
-        (else_bcx_in, join_blocks(bcx, [then_bcx_out, else_bcx_out]))
+          let (else_bcx_in, else_bcx_out) = trans_if_else(bcx, elexpr, dest, "else");
+          (else_bcx_in, join_blocks(bcx, [then_bcx_out, else_bcx_out]))
       }
       _ => {
           let next_bcx = sub_block(bcx, "next");
@@ -109,7 +127,27 @@ pub fn trans_if(bcx: block,
            then_bcx_in.to_str(), else_bcx_in.to_str());
 
     CondBr(bcx, cond_val, then_bcx_in.llbb, else_bcx_in.llbb);
-    next_bcx
+    return next_bcx;
+
+    // trans `else [ if { .. } ... | { .. } ]`
+    fn trans_if_else(bcx: block, elexpr: @ast::expr,
+                     dest: expr::Dest, scope_name: &str) -> (block, block) {
+        let else_bcx_in = scope_block(bcx, elexpr.info(), scope_name);
+        let else_bcx_out = match elexpr.node {
+            ast::expr_if(_, _, _) => {
+                let elseif_blk = ast_util::block_from_expr(elexpr);
+                trans_block(else_bcx_in, &elseif_blk, dest)
+            }
+            ast::expr_block(ref blk) => {
+                trans_block(else_bcx_in, blk, dest)
+            }
+            // would be nice to have a constraint on ifs
+            _ => bcx.tcx().sess.bug("strange alternative in if")
+        };
+        let else_bcx_out = trans_block_cleanups(else_bcx_out,
+                                                block_cleanups(else_bcx_in));
+        (else_bcx_in, else_bcx_out)
+    }
 }
 
 pub fn join_blocks(parent_bcx: block, in_cxs: &[block]) -> block {

src/librustc/middle/trans/datum.rs

@@ -413,7 +413,7 @@ impl Datum {
     pub fn to_value_datum(&self, bcx: block) -> Datum {
         /*!
          *
-         * Yields a by-ref form of this datum.  This may involve
+         * Yields a by-value form of this datum.  This may involve
          * creation of a temporary stack slot.  The value returned by
          * this function is not separately rooted from this datum, so
          * it will not live longer than the current datum. */

src/librustdoc/astsrv.rs

@@ -113,6 +113,8 @@ fn build_ctxt(sess: Session,
 
     use rustc::front::config;
 
+    let ast = syntax::ext::expand::inject_std_macros(sess.parse_sess,
+                                                     copy sess.opts.cfg, ast);
     let ast = config::strip_unconfigured_items(ast);
     let ast = syntax::ext::expand::expand_crate(sess.parse_sess,
                                                 copy sess.opts.cfg, ast);
@@ -138,7 +140,8 @@ fn should_prune_unconfigured_items() {
     let source = ~"#[cfg(shut_up_and_leave_me_alone)]fn a() { }";
     do from_str(source) |srv| {
         do exec(srv) |ctxt| {
-            assert!(ctxt.ast.node.module.items.is_empty());
+            // one item: the __std_macros secret module
+            assert_eq!(ctxt.ast.node.module.items.len(), 1);
         }
     }
 }

src/librustdoc/attr_pass.rs

@@ -255,7 +255,8 @@ mod test {
     #[test]
     fn should_should_extract_mod_attributes() {
         let doc = mk_doc(~"#[doc = \"test\"] mod a { }");
-        assert!(doc.cratemod().mods()[0].desc() == Some(~"test"));
+        // hidden __std_macros module at the start.
+        assert!(doc.cratemod().mods()[1].desc() == Some(~"test"));
     }
 
     #[test]

src/librustdoc/desc_to_brief_pass.rs

@@ -190,7 +190,8 @@ mod test {
     #[test]
     fn should_promote_desc() {
         let doc = mk_doc(~"#[doc = \"desc\"] mod m { }");
-        assert_eq!(doc.cratemod().mods()[0].brief(), Some(~"desc"));
+        // hidden __std_macros module at the start.
+        assert_eq!(doc.cratemod().mods()[1].brief(), Some(~"desc"));
     }
 
     #[test]

src/librustdoc/markdown_index_pass.rs

@@ -172,6 +172,7 @@ mod test {
     use extract;
     use markdown_index_pass::run;
     use path_pass;
+    use prune_hidden_pass;
     use super::pandoc_header_id;
 
     fn mk_doc(output_style: config::OutputStyle, source: ~str)
@@ -183,8 +184,10 @@ mod test {
             };
             let doc = extract::from_srv(srv.clone(), ~"");
             let doc = (attr_pass::mk_pass().f)(srv.clone(), doc);
+            let doc = (prune_hidden_pass::mk_pass().f)(srv.clone(), doc);
             let doc = (desc_to_brief_pass::mk_pass().f)(srv.clone(), doc);
             let doc = (path_pass::mk_pass().f)(srv.clone(), doc);
+
             run(srv.clone(), doc, config)
         }
     }
@@ -240,13 +243,13 @@ mod test {
             config::DocPerMod,
             ~"mod a { } fn b() { }"
         );
-        assert!(doc.cratemod().index.get().entries[0] == doc::IndexEntry {
+        assert_eq!(doc.cratemod().index.get().entries[0], doc::IndexEntry {
             kind: ~"Module",
             name: ~"a",
             brief: None,
             link: ~"a.html"
         });
-        assert!(doc.cratemod().index.get().entries[1] == doc::IndexEntry {
+        assert_eq!(doc.cratemod().index.get().entries[1], doc::IndexEntry {
             kind: ~"Function",
             name: ~"b",
             brief: None,
@@ -260,8 +263,7 @@ mod test {
             config::DocPerMod,
             ~"#[doc = \"test\"] mod a { }"
         );
-        assert!(doc.cratemod().index.get().entries[0].brief
-                == Some(~"test"));
+        assert_eq!(doc.cratemod().index.get().entries[0].brief, Some(~"test"));
     }
 
     #[test]
@@ -270,12 +272,13 @@ mod test {
             config::DocPerCrate,
             ~"extern { fn b(); }"
         );
-        assert!(doc.cratemod().nmods()[0].index.get().entries[0]
-                == doc::IndexEntry {
-                    kind: ~"Function",
-                    name: ~"b",
-                    brief: None,
-                    link: ~"#function-b"
-                });
+        // hidden __std_macros module at the start.
+        assert_eq!(doc.cratemod().nmods()[0].index.get().entries[0],
+                   doc::IndexEntry {
+                       kind: ~"Function",
+                       name: ~"b",
+                       brief: None,
+                       link: ~"#function-b"
+                   });
     }
 }

src/librustdoc/markdown_pass.rs

@@ -529,6 +529,7 @@ mod test {
     use markdown_writer;
     use path_pass;
     use page_pass;
+    use prune_hidden_pass;
     use sectionalize_pass;
     use trim_pass;
     use tystr_pass;
@@ -557,6 +558,8 @@ mod test {
             debug!("doc (path): %?", doc);
             let doc = (attr_pass::mk_pass().f)(srv.clone(), doc);
             debug!("doc (attr): %?", doc);
+            let doc = (prune_hidden_pass::mk_pass().f)(srv.clone(), doc);
+            debug!("doc (prune_hidden): %?", doc);
             let doc = (desc_to_brief_pass::mk_pass().f)(srv.clone(), doc);
             debug!("doc (desc_to_brief): %?", doc);
             let doc = (unindent_pass::mk_pass().f)(srv.clone(), doc);

src/librustdoc/markdown_writer.rs

@@ -277,7 +277,8 @@ mod test {
             .. config::default_config(&Path("input/test.rc"))
         };
         let doc = mk_doc(~"", ~"mod a { mod b { } }");
-        let modb = copy doc.cratemod().mods()[0].mods()[0];
+        // hidden __std_macros module at the start.
+        let modb = copy doc.cratemod().mods()[1].mods()[0];
         let page = doc::ItemPage(doc::ModTag(modb));
         let filename = make_local_filename(&config, page);
         assert_eq!(filename, Path("output/dir/a_b.html"));

src/librustdoc/page_pass.rs

@@ -152,8 +152,10 @@ fn fold_nmod(
 mod test {
     use astsrv;
     use config;
+    use attr_pass;
     use doc;
     use extract;
+    use prune_hidden_pass;
     use page_pass::run;
 
     fn mk_doc_(
@@ -162,6 +164,8 @@ mod test {
     ) -> doc::Doc {
         do astsrv::from_str(copy source) |srv| {
             let doc = extract::from_srv(srv.clone(), ~"");
+            let doc = (attr_pass::mk_pass().f)(srv.clone(), doc);
+            let doc = (prune_hidden_pass::mk_pass().f)(srv.clone(), doc);
             run(srv.clone(), doc, output_style)
         }
     }
@@ -182,6 +186,7 @@ mod test {
     #[test]
     fn should_make_a_page_for_every_mod() {
         let doc = mk_doc(~"mod a { }");
+        // hidden __std_macros module at the start.
         assert_eq!(doc.pages.mods()[0].name(), ~"a");
     }
 

src/librustdoc/path_pass.rs

@@ -97,10 +97,11 @@ fn should_record_mod_paths() {
     do astsrv::from_str(source) |srv| {
         let doc = extract::from_srv(srv.clone(), ~"");
         let doc = run(srv.clone(), doc);
-        assert!(doc.cratemod().mods()[0].mods()[0].mods()[0].path()
-            == ~[~"a", ~"b"]);
-        assert!(doc.cratemod().mods()[0].mods()[1].mods()[0].path()
-            == ~[~"a", ~"d"]);
+        // hidden __std_macros module at the start.
+        assert_eq!(doc.cratemod().mods()[1].mods()[0].mods()[0].path(),
+                   ~[~"a", ~"b"]);
+        assert_eq!(doc.cratemod().mods()[1].mods()[1].mods()[0].path(),
+                   ~[~"a", ~"d"]);
     }
 }
 
@@ -110,6 +111,7 @@ fn should_record_fn_paths() {
     do astsrv::from_str(source) |srv| {
         let doc = extract::from_srv(srv.clone(), ~"");
         let doc = run(srv.clone(), doc);
-        assert_eq!(doc.cratemod().mods()[0].fns()[0].path(), ~[~"a"]);
+        // hidden __std_macros module at the start.
+        assert_eq!(doc.cratemod().mods()[1].fns()[0].path(), ~[~"a"]);
     }
 }

src/librustdoc/sectionalize_pass.rs

@@ -166,12 +166,14 @@ mod test {
     use attr_pass;
     use doc;
     use extract;
+    use prune_hidden_pass;
     use sectionalize_pass::run;
 
     fn mk_doc(source: ~str) -> doc::Doc {
         do astsrv::from_str(copy source) |srv| {
             let doc = extract::from_srv(srv.clone(), ~"");
             let doc = (attr_pass::mk_pass().f)(srv.clone(), doc);
+            let doc = (prune_hidden_pass::mk_pass().f)(srv.clone(), doc);
             run(srv.clone(), doc)
         }
     }

src/librustdoc/sort_item_name_pass.rs

@@ -31,7 +31,8 @@ fn test() {
     do astsrv::from_str(source) |srv| {
         let doc = extract::from_srv(srv.clone(), ~"");
         let doc = (mk_pass().f)(srv.clone(), doc);
-        assert_eq!(doc.cratemod().items[0].name(), ~"y");
-        assert_eq!(doc.cratemod().items[1].name(), ~"z");
+        // hidden __std_macros module at the start.
+        assert_eq!(doc.cratemod().items[1].name(), ~"y");
+        assert_eq!(doc.cratemod().items[2].name(), ~"z");
     }
 }

src/librustdoc/sort_item_type_pass.rs

@@ -53,13 +53,15 @@ fn test() {
     do astsrv::from_str(source) |srv| {
         let doc = extract::from_srv(srv.clone(), ~"");
         let doc = (mk_pass().f)(srv.clone(), doc);
+        // hidden __std_macros module at the start.
         assert_eq!(doc.cratemod().items[0].name(), ~"iconst");
         assert_eq!(doc.cratemod().items[1].name(), ~"itype");
         assert_eq!(doc.cratemod().items[2].name(), ~"ienum");
         assert_eq!(doc.cratemod().items[3].name(), ~"istruct");
         assert_eq!(doc.cratemod().items[4].name(), ~"itrait");
         assert_eq!(doc.cratemod().items[5].name(), ~"__extensions__");
         assert_eq!(doc.cratemod().items[6].name(), ~"ifn");
-        assert_eq!(doc.cratemod().items[7].name(), ~"imod");
+        // hidden __std_macros module fits here.
+        assert_eq!(doc.cratemod().items[8].name(), ~"imod");
     }
 }