simplify-locals: Remove unused set-discriminant statements

tmiasko · tmiasko · commit 52d37826858e · 2020-10-26T10:41:44.000+01:00
Update affected ui &amp; incremental tests to use a user declared variable
bindings instead of temporaries. The former are preserved because of
debuginfo, the latter are not.
diff --git a/compiler/rustc_mir/src/transform/simplify.rs b/compiler/rustc_mir/src/transform/simplify.rs
@@ -427,7 +427,6 @@ impl Visitor<'_> for UsedLocals {
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
         match statement.kind {
             StatementKind::LlvmInlineAsm(..)
-            | StatementKind::SetDiscriminant { .. } // FIXME: Try to remove those as well.
             | StatementKind::Retag(..)
             | StatementKind::Coverage(..)
             | StatementKind::FakeRead(..)
@@ -467,6 +466,10 @@ impl Visitor<'_> for UsedLocals {
                 }
                 self.visit_rvalue(rvalue, location);
             }
+
+            StatementKind::SetDiscriminant { ref place, variant_index: _ } => {
+                self.visit_lhs(place, location);
+            }
         }
     }
 
@@ -481,10 +484,7 @@ impl Visitor<'_> for UsedLocals {
 }
 
 /// Removes unused definitions. Updates the used locals to reflect the changes made.
-fn remove_unused_definitions<'a, 'tcx>(
-    used_locals: &'a mut UsedLocals,
-    body: &mut Body<'tcx>,
-) {
+fn remove_unused_definitions<'a, 'tcx>(used_locals: &'a mut UsedLocals, body: &mut Body<'tcx>) {
     // The use counts are updated as we remove the statements. A local might become unused
     // during the retain operation, leading to a temporary inconsistency (storage statements or
     // definitions referencing the local might remain). For correctness it is crucial that this
@@ -502,6 +502,10 @@ fn remove_unused_definitions<'a, 'tcx>(
                         used_locals.is_used(*local)
                     }
                     StatementKind::Assign(box (place, _)) => used_locals.is_used(place.local),
+
+                    StatementKind::SetDiscriminant { ref place, .. } => {
+                        used_locals.is_used(place.local)
+                    }
                     _ => true,
                 };
 
diff --git a/src/test/incremental/hashes/enum_constructors.rs b/src/test/incremental/hashes/enum_constructors.rs
@@ -7,7 +7,7 @@
 
 // build-pass (FIXME(62277): could be check-pass?)
 // revisions: cfail1 cfail2 cfail3
-// compile-flags: -Z query-dep-graph -Zincremental-ignore-spans
+// compile-flags: -Z query-dep-graph -Zincremental-ignore-spans -Zmir-opt-level=0
 
 #![allow(warnings)]
 #![feature(rustc_attrs)]
diff --git a/src/test/mir-opt/simplify_locals.d1.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.d1.SimplifyLocals.diff
@@ -3,14 +3,14 @@
   
   fn d1() -> () {
       let mut _0: ();                      // return place in scope 0 at $DIR/simplify-locals.rs:20:9: 20:9
-      let mut _1: E;                       // in scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
+-     let mut _1: E;                       // in scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
       scope 1 {
       }
   
       bb0: {
-          StorageLive(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
-          discriminant(_1) = 0;            // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
-          StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:17: 22:18
+-         StorageLive(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
+-         discriminant(_1) = 0;            // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
+-         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:17: 22:18
           _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:20:9: 23:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:23:2: 23:2
       }
diff --git a/src/test/mir-opt/simplify_locals.d2.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.d2.SimplifyLocals.diff
@@ -3,14 +3,13 @@
   
   fn d2() -> () {
       let mut _0: ();                      // return place in scope 0 at $DIR/simplify-locals.rs:26:9: 26:9
-      let mut _1: E;                       // in scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
+-     let mut _1: E;                       // in scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
 -     let mut _2: (i32, E);                // in scope 0 at $DIR/simplify-locals.rs:28:5: 28:17
 -     let mut _3: E;                       // in scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
-+     let mut _2: E;                       // in scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
   
       bb0: {
-          StorageLive(_1);                 // scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
-          discriminant(_1) = 1;            // scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
+-         StorageLive(_1);                 // scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
+-         discriminant(_1) = 1;            // scope 0 at $DIR/simplify-locals.rs:28:22: 28:26
 -         StorageLive(_2);                 // scope 0 at $DIR/simplify-locals.rs:28:5: 28:17
 -         StorageLive(_3);                 // scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
 -         discriminant(_3) = 0;            // scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
@@ -30,10 +29,7 @@
 -                                          // mir::Constant
 -                                          // + span: $DIR/simplify-locals.rs:28:5: 28:26
 -                                          // + literal: Const { ty: E, val: Value(Scalar(0x01)) }
-+         StorageLive(_2);                 // scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
-+         discriminant(_2) = 0;            // scope 0 at $DIR/simplify-locals.rs:28:11: 28:15
-+         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:28:15: 28:16
-          StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:28:25: 28:26
+-         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:28:25: 28:26
 -         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:28:26: 28:27
           _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:26:9: 29:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:29:2: 29:2
diff --git a/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.32bit.mir b/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.32bit.mir
@@ -3,18 +3,14 @@
 fn change_loop_body() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/while_let_loops.rs:5:27: 5:27
     let mut _1: i32;                     // in scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
-    let mut _2: std::option::Option<u32>; // in scope 0 at $DIR/while_let_loops.rs:7:28: 7:32
     scope 1 {
         debug _x => _1;                  // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
     }
 
     bb0: {
         StorageLive(_1);                 // scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
         _1 = const 0_i32;                // scope 0 at $DIR/while_let_loops.rs:6:18: 6:19
-        StorageLive(_2);                 // scope 1 at $DIR/while_let_loops.rs:7:28: 7:32
-        discriminant(_2) = 0;            // scope 1 at $DIR/while_let_loops.rs:7:28: 7:32
         _0 = const ();                   // scope 1 at $DIR/while_let_loops.rs:7:5: 10:6
-        StorageDead(_2);                 // scope 1 at $DIR/while_let_loops.rs:10:5: 10:6
         StorageDead(_1);                 // scope 0 at $DIR/while_let_loops.rs:11:1: 11:2
         return;                          // scope 0 at $DIR/while_let_loops.rs:11:2: 11:2
     }
diff --git a/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.64bit.mir b/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.64bit.mir
@@ -3,18 +3,14 @@
 fn change_loop_body() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/while_let_loops.rs:5:27: 5:27
     let mut _1: i32;                     // in scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
-    let mut _2: std::option::Option<u32>; // in scope 0 at $DIR/while_let_loops.rs:7:28: 7:32
     scope 1 {
         debug _x => _1;                  // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
     }
 
     bb0: {
         StorageLive(_1);                 // scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
         _1 = const 0_i32;                // scope 0 at $DIR/while_let_loops.rs:6:18: 6:19
-        StorageLive(_2);                 // scope 1 at $DIR/while_let_loops.rs:7:28: 7:32
-        discriminant(_2) = 0;            // scope 1 at $DIR/while_let_loops.rs:7:28: 7:32
         _0 = const ();                   // scope 1 at $DIR/while_let_loops.rs:7:5: 10:6
-        StorageDead(_2);                 // scope 1 at $DIR/while_let_loops.rs:10:5: 10:6
         StorageDead(_1);                 // scope 0 at $DIR/while_let_loops.rs:11:1: 11:2
         return;                          // scope 0 at $DIR/while_let_loops.rs:11:2: 11:2
     }
diff --git a/src/test/ui/lint/issue-69485-var-size-diffs-too-large.rs b/src/test/ui/lint/issue-69485-var-size-diffs-too-large.rs
@@ -1,5 +1,6 @@
 // build-fail
 // only-x86_64
+// compile-flags: -Zmir-opt-level=0
 
 fn main() {
     Bug::V([0; !0]); //~ ERROR is too big for the current
diff --git a/src/test/ui/lint/issue-69485-var-size-diffs-too-large.stderr b/src/test/ui/lint/issue-69485-var-size-diffs-too-large.stderr
@@ -1,5 +1,5 @@
 error: the type `[u8; 18446744073709551615]` is too big for the current architecture
-  --> $DIR/issue-69485-var-size-diffs-too-large.rs:5:12
+  --> $DIR/issue-69485-var-size-diffs-too-large.rs:6:12
    |
 LL |     Bug::V([0; !0]);
    |            ^^^^^^^

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,5 @@`
`1`	`1`	error: the type `[u8; 18446744073709551615]` is too big for the current architecture
`2`		`- --> $DIR/issue-69485-var-size-diffs-too-large.rs:5:12`
	`2`	`+ --> $DIR/issue-69485-var-size-diffs-too-large.rs:6:12`
`3`	`3`	`\|`
`4`	`4`	`LL \| Bug::V([0; !0]);`
`5`	`5`	`\| ^^^^^^^`