remove type_use

This is broken, and results in poor performance due to the undefined
behaviour in the LLVM IR. LLVM's `mergefunc` is a *much* better way of
doing this since it merges based on the equality of the bytecode.

For example, consider `std::repr`. It generates different code per
type, but is not included in the type bounds of generics.

The `mergefunc` pass works for most of our code but currently hits an
assert on libstd. It is receiving attention upstream so it will be
ready soon, but I don't think removing this broken code should wait any
longer. I've opened #9536 about enabling it by default.

Closes #8651
Closes #3547
Closes #2537
Closes #6971
Closes #9222

src/etc/zsh/_rust

@@ -71,7 +71,6 @@ _rustc_opts_debug=(
     'count-type-sizes:count the sizes of aggregate types'
     'meta-stats:gather metadata statistics'
     'no-opt:do not optimize, even if -O is passed'
-    'no-monomorphic-collapse:do not collapse template instantiations'
     'print-link-args:Print the arguments passed to the linker'
     'gc:Garbage collect shared data (experimental)'
     'jit:Execute using JIT (experimental)'

src/librustc/driver/driver.rs

@@ -748,13 +748,6 @@ pub fn build_session_options(binary: @str,
     let debuginfo = debugging_opts & session::debug_info != 0 ||
         extra_debuginfo;
 
-    // If debugging info is generated, do not collapse monomorphized function instances.
-    // Functions with equivalent llvm code still need separate debugging descriptions because names
-    // might differ.
-    if debuginfo {
-        debugging_opts |= session::no_monomorphic_collapse;
-    }
-
     let statik = debugging_opts & session::statik != 0;
 
     let addl_lib_search_paths = matches.opt_strs("L").map(|s| Path(*s));

src/librustc/driver/session.rs

@@ -67,20 +67,19 @@ pub static debug_llvm:              uint = 1 << 13;
 pub static count_type_sizes:        uint = 1 << 14;
 pub static meta_stats:              uint = 1 << 15;
 pub static no_opt:                  uint = 1 << 16;
-pub static no_monomorphic_collapse: uint = 1 << 17;
-pub static gc:                      uint = 1 << 18;
-pub static jit:                     uint = 1 << 19;
-pub static debug_info:              uint = 1 << 20;
-pub static extra_debug_info:        uint = 1 << 21;
-pub static statik:                  uint = 1 << 22;
-pub static print_link_args:         uint = 1 << 23;
-pub static no_debug_borrows:        uint = 1 << 24;
-pub static lint_llvm:               uint = 1 << 25;
-pub static once_fns:                uint = 1 << 26;
-pub static print_llvm_passes:       uint = 1 << 27;
-pub static no_vectorize_loops:      uint = 1 << 28;
-pub static no_vectorize_slp:        uint = 1 << 29;
-pub static no_prepopulate_passes:   uint = 1 << 30;
+pub static gc:                      uint = 1 << 17;
+pub static jit:                     uint = 1 << 18;
+pub static debug_info:              uint = 1 << 19;
+pub static extra_debug_info:        uint = 1 << 20;
+pub static statik:                  uint = 1 << 21;
+pub static print_link_args:         uint = 1 << 22;
+pub static no_debug_borrows:        uint = 1 << 23;
+pub static lint_llvm:               uint = 1 << 24;
+pub static once_fns:                uint = 1 << 25;
+pub static print_llvm_passes:       uint = 1 << 26;
+pub static no_vectorize_loops:      uint = 1 << 27;
+pub static no_vectorize_slp:        uint = 1 << 28;
+pub static no_prepopulate_passes:   uint = 1 << 29;
 
 pub fn debugging_opts_map() -> ~[(~str, ~str, uint)] {
     ~[(~"verbose", ~"in general, enable more debug printouts", verbose),
@@ -106,8 +105,6 @@ pub fn debugging_opts_map() -> ~[(~str, ~str, uint)] {
       count_type_sizes),
      (~"meta-stats", ~"gather metadata statistics", meta_stats),
      (~"no-opt", ~"do not optimize, even if -O is passed", no_opt),
-     (~"no-monomorphic-collapse", ~"do not collapse template instantiations",
-      no_monomorphic_collapse),
      (~"print-link-args", ~"Print the arguments passed to the linker", print_link_args),
      (~"gc", ~"Garbage collect shared data (experimental)", gc),
      (~"jit", ~"Execute using JIT (experimental)", jit),
@@ -326,9 +323,6 @@ impl Session_ {
     pub fn borrowck_note_loan(&self) -> bool {
         self.debugging_opt(borrowck_note_loan)
     }
-    pub fn no_monomorphic_collapse(&self) -> bool {
-        self.debugging_opt(no_monomorphic_collapse)
-    }
     pub fn debug_borrows(&self) -> bool {
         self.opts.optimize == No && !self.debugging_opt(no_debug_borrows)
     }

src/librustc/middle/trans/context.rs

@@ -22,7 +22,6 @@ use middle::trans::adt;
 use middle::trans::base;
 use middle::trans::builder::Builder;
 use middle::trans::debuginfo;
-use middle::trans::type_use;
 use middle::trans::common::{C_i32, C_null};
 use middle::ty;
 
@@ -73,8 +72,6 @@ pub struct CrateContext {
      // Cache instances of monomorphized functions
      monomorphized: HashMap<mono_id, ValueRef>,
      monomorphizing: HashMap<ast::DefId, uint>,
-     // Cache computed type parameter uses (see type_use.rs)
-     type_use_cache: HashMap<ast::DefId, @~[type_use::type_uses]>,
      // Cache generated vtables
      vtables: HashMap<(ty::t, mono_id), ValueRef>,
      // Cache of constant strings,
@@ -204,7 +201,6 @@ impl CrateContext {
                   non_inlineable_statics: HashSet::new(),
                   monomorphized: HashMap::new(),
                   monomorphizing: HashMap::new(),
-                  type_use_cache: HashMap::new(),
                   vtables: HashMap::new(),
                   const_cstr_cache: HashMap::new(),
                   const_globals: HashMap::new(),

src/librustc/middle/trans/meth.rs

@@ -520,8 +520,7 @@ pub fn vtable_id(ccx: @mut CrateContext,
             monomorphize::make_mono_id(
                 ccx,
                 impl_id,
-                &psubsts,
-                None)
+                &psubsts)
         }
 
         // can't this be checked at the callee?

src/librustc/middle/trans/mod.rs

@@ -38,7 +38,6 @@ pub mod foreign;
 pub mod intrinsic;
 pub mod reflect;
 pub mod debuginfo;
-pub mod type_use;
 pub mod machine;
 pub mod adt;
 pub mod asm;

src/librustc/middle/trans/monomorphize.rs

@@ -18,15 +18,11 @@ use middle::trans::base::{trans_fn, decl_internal_rust_fn};
 use middle::trans::base::{get_item_val, no_self};
 use middle::trans::base;
 use middle::trans::common::*;
-use middle::trans::datum;
-use middle::trans::machine;
 use middle::trans::meth;
-use middle::trans::type_of;
-use middle::trans::type_use;
 use middle::trans::intrinsic;
 use middle::ty;
 use middle::typeck;
-use util::ppaux::{Repr,ty_to_str};
+use util::ppaux::Repr;
 
 use syntax::ast;
 use syntax::ast_map;
@@ -65,10 +61,8 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
 
     for s in real_substs.tps.iter() { assert!(!ty::type_has_params(*s)); }
     for s in psubsts.tys.iter() { assert!(!ty::type_has_params(*s)); }
-    let param_uses = type_use::type_uses_for(ccx, fn_id, psubsts.tys.len());
 
-
-    let hash_id = make_mono_id(ccx, fn_id, &*psubsts, Some(param_uses));
+    let hash_id = make_mono_id(ccx, fn_id, &*psubsts);
     if hash_id.params.iter().any(
                 |p| match *p { mono_precise(_, _) => false, _ => true }) {
         must_cast = true;
@@ -302,8 +296,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
 
 pub fn make_mono_id(ccx: @mut CrateContext,
                     item: ast::DefId,
-                    substs: &param_substs,
-                    param_uses: Option<@~[type_use::type_uses]>) -> mono_id {
+                    substs: &param_substs) -> mono_id {
     // FIXME (possibly #5801): Need a lot of type hints to get
     // .collect() to work.
     let substs_iter = substs.self_ty.iter().chain(substs.tys.iter());
@@ -321,59 +314,9 @@ pub fn make_mono_id(ccx: @mut CrateContext,
     };
 
 
-    let param_ids = match param_uses {
-      Some(ref uses) => {
-        // param_uses doesn't include a use for the self type.
-        // We just say it is fully used.
-        let self_use =
-            substs.self_ty.map(|_| type_use::use_repr|type_use::use_tydesc);
-        let uses_iter = self_use.iter().chain(uses.iter());
-
-        precise_param_ids.iter().zip(uses_iter).map(|(id, uses)| {
-            if ccx.sess.no_monomorphic_collapse() {
-                match *id {
-                    (a, b) => mono_precise(a, b)
-                }
-            } else {
-                match *id {
-                    (a, b@Some(_)) => mono_precise(a, b),
-                    (subst, None) => {
-                        if *uses == 0 {
-                            mono_any
-                        } else if *uses == type_use::use_repr &&
-                            !ty::type_needs_drop(ccx.tcx, subst)
-                        {
-                            let llty = type_of::type_of(ccx, subst);
-                            let size = machine::llbitsize_of_real(ccx, llty);
-                            let align = machine::llalign_of_min(ccx, llty);
-                            let mode = datum::appropriate_mode(ccx.tcx, subst);
-                            let data_class = mono_data_classify(subst);
-
-                            debug!("make_mono_id: type %s -> size %u align %u mode %? class %?",
-                                  ty_to_str(ccx.tcx, subst),
-                                  size, align, mode, data_class);
-
-                            // Special value for nil to prevent problems
-                            // with undef return pointers.
-                            if size <= 8u && ty::type_is_nil(subst) {
-                                mono_repr(0u, 0u, data_class, mode)
-                            } else {
-                                mono_repr(size, align, data_class, mode)
-                            }
-                        } else {
-                            mono_precise(subst, None)
-                        }
-                    }
-                }
-            }
-        }).collect()
-      }
-      None => {
-          precise_param_ids.iter().map(|x| {
-              let (a, b) = *x;
-              mono_precise(a, b)
-          }).collect()
-      }
-    };
+    let param_ids = precise_param_ids.iter().map(|x| {
+        let (a, b) = *x;
+        mono_precise(a, b)
+    }).collect();
     @mono_id_ {def: item, params: param_ids}
 }