[WIP] Compute always-storage-liveness more efficiently

Cargo.lock

@@ -307,7 +307,7 @@ dependencies = [
  "cargo-test-macro",
  "cargo-test-support",
  "cargo-util",
- "clap",
+ "clap 3.2.5",
  "crates-io",
  "crossbeam-utils",
  "curl",
@@ -572,6 +572,22 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "clap"
+version = "2.34.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0610544180c38b88101fecf2dd634b174a62eef6946f84dfc6a7127512b381c"
+dependencies = [
+ "ansi_term",
+ "atty",
+ "bitflags",
+ "strsim 0.8.0",
+ "textwrap 0.11.0",
+ "unicode-width",
+ "vec_map",
+ "yaml-rust 0.3.5",
+]
+
 [[package]]
 name = "clap"
 version = "3.2.5"
@@ -584,9 +600,9 @@ dependencies = [
  "clap_lex",
  "indexmap",
  "once_cell",
- "strsim",
+ "strsim 0.10.0",
  "termcolor",
- "textwrap",
+ "textwrap 0.15.0",
 ]
 
 [[package]]
@@ -595,7 +611,7 @@ version = "3.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "df6f3613c0a3cddfd78b41b10203eb322cb29b600cbdf808a7d3db95691b8e25"
 dependencies = [
- "clap",
+ "clap 3.2.5",
 ]
 
 [[package]]
@@ -653,7 +669,7 @@ name = "clippy_dev"
 version = "0.0.1"
 dependencies = [
  "aho-corasick",
- "clap",
+ "clap 3.2.5",
  "indoc",
  "itertools",
  "opener",
@@ -1226,7 +1242,7 @@ name = "expand-yaml-anchors"
 version = "0.1.0"
 dependencies = [
  "yaml-merge-keys",
- "yaml-rust",
+ "yaml-rust 0.4.4",
 ]
 
 [[package]]
@@ -1846,7 +1862,7 @@ name = "installer"
 version = "0.0.0"
 dependencies = [
  "anyhow",
- "clap",
+ "clap 2.34.0",
  "flate2",
  "lazy_static",
  "num_cpus",
@@ -2294,7 +2310,7 @@ dependencies = [
  "ammonia",
  "anyhow",
  "chrono",
- "clap",
+ "clap 3.2.5",
  "clap_complete",
  "elasticlunr-rs",
  "env_logger 0.7.1",
@@ -3369,7 +3385,7 @@ dependencies = [
 name = "rustbook"
 version = "0.1.0"
 dependencies = [
- "clap",
+ "clap 3.2.5",
  "env_logger 0.7.1",
  "mdbook",
 ]
@@ -3457,7 +3473,7 @@ version = "1.0.0"
 dependencies = [
  "bstr",
  "byteorder",
- "clap",
+ "clap 3.2.5",
  "crossbeam-utils",
  "libc",
  "libz-sys",
@@ -4646,7 +4662,7 @@ dependencies = [
  "anyhow",
  "bytecount",
  "cargo_metadata",
- "clap",
+ "clap 3.2.5",
  "derive-new",
  "diff",
  "dirs",
@@ -5037,6 +5053,12 @@ dependencies = [
  "vte",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
+
 [[package]]
 name = "strsim"
 version = "0.10.0"
@@ -5177,6 +5199,15 @@ dependencies = [
  "term",
 ]
 
+[[package]]
+name = "textwrap"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
+dependencies = [
+ "unicode-width",
+]
+
 [[package]]
 name = "textwrap"
 version = "0.15.0"
@@ -5697,6 +5728,12 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6454029bf181f092ad1b853286f23e2c507d8e8194d01d92da4a55c274a5508c"
 
+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
 [[package]]
 name = "vergen"
 version = "5.1.0"
@@ -5855,9 +5892,15 @@ checksum = "fd236a7dc9bb598f349fe4a8754f49181fee50284daa15cd1ba652d722280004"
 dependencies = [
  "lazy_static",
  "thiserror",
- "yaml-rust",
+ "yaml-rust 0.4.4",
 ]
 
+[[package]]
+name = "yaml-rust"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e66366e18dc58b46801afbf2ca7661a9f59cc8c5962c29892b6039b4f86fa992"
+
 [[package]]
 name = "yaml-rust"
 version = "0.4.4"

compiler/rustc_middle/src/mir/mod.rs

@@ -824,6 +824,10 @@ pub struct LocalDecl<'tcx> {
     ///  │ │← `drop(x)` // This accesses `x: u32`.
     /// ```
     pub source_info: SourceInfo,
+
+    /// `true` if the local has a fixed storage for the duration of the body
+    /// (that is, it does not have `StorageLive`/`StorageDead` annotations).
+    pub always_storage_live: bool,
 }
 
 // `LocalDecl` is used a lot. Make sure it doesn't unintentionally get bigger.
@@ -949,6 +953,7 @@ impl<'tcx> LocalDecl<'tcx> {
             ty,
             user_ty: None,
             source_info,
+            always_storage_live: false,
         }
     }
 

compiler/rustc_middle/src/mir/visit.rs

@@ -867,6 +867,7 @@ macro_rules! make_mir_visitor {
                     internal: _,
                     local_info: _,
                     is_block_tail: _,
+                    always_storage_live: _,
                 } = local_decl;
 
                 self.visit_ty($(& $mutability)? *ty, TyContext::LocalDecl {

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -2241,6 +2241,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     pat_span,
                 },
             ))))),
+            always_storage_live: false,
         };
         let for_arm_body = self.local_decls.push(local);
         self.var_debug_info.push(VarDebugInfo {
@@ -2261,6 +2262,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 local_info: Some(Box::new(LocalInfo::User(ClearCrossCrate::Set(
                     BindingForm::RefForGuard,
                 )))),
+                always_storage_live: false,
             });
             self.var_debug_info.push(VarDebugInfo {
                 name,

compiler/rustc_mir_dataflow/src/storage.rs

@@ -1,21 +1,16 @@
 use rustc_index::bit_set::BitSet;
-use rustc_middle::mir::{self, Local};
+use rustc_middle::mir::{self, HasLocalDecls, Local};
 
-/// The set of locals in a MIR body that do not have `StorageLive`/`StorageDead` annotations.
+/// Returns the set of locals in a MIR body that do not have `StorageLive`/`StorageDead`
+/// annotations.
 ///
 /// These locals have fixed storage for the duration of the body.
-//
-// FIXME: Currently, we need to traverse the entire MIR to compute this. We should instead store it
-// as a field in the `LocalDecl` for each `Local`.
-pub fn always_storage_live_locals(body: &mir::Body<'_>) -> BitSet<Local> {
+pub fn always_live_locals(body: &mir::Body<'_>) -> BitSet<Local> {
     let mut always_live_locals = BitSet::new_filled(body.local_decls.len());
 
-    for block in body.basic_blocks() {
-        for statement in &block.statements {
-            use mir::StatementKind::{StorageDead, StorageLive};
-            if let StorageLive(l) | StorageDead(l) = statement.kind {
-                always_live_locals.remove(l);
-            }
+    for (local, local_decl) in body.local_decls().iter_enumerated() {
+        if !local_decl.always_storage_live {
+            always_live_locals.remove(local);
         }
     }