Auto merge of #109900 - cjgillot:disable-const-prop, r=oli-obk

Only enable ConstProp at mir-opt-level >= 2.

That pass is not responsible for lints any more, so we can restrict it to optimized builds.

This reduces the amount of duplicated const-eval messages.

Author: bors

compiler/rustc_mir_transform/src/const_prop.rs

@@ -54,7 +54,7 @@ pub struct ConstProp;
 
 impl<'tcx> MirPass<'tcx> for ConstProp {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 1
+        sess.mir_opt_level() >= 2
     }
 
     #[instrument(skip(self, tcx), level = "debug")]
@@ -854,12 +854,6 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
         }
     }
 
-    fn visit_constant(&mut self, constant: &mut Constant<'tcx>, location: Location) {
-        trace!("visit_constant: {:?}", constant);
-        self.super_constant(constant, location);
-        self.eval_constant(constant);
-    }
-
     fn visit_assign(
         &mut self,
         place: &mut Place<'tcx>,

compiler/rustc_mir_transform/src/lib.rs

@@ -566,8 +566,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &separate_const_switch::SeparateConstSwitch,
             &simplify::SimplifyLocals::new("before-const-prop"),
             &copy_prop::CopyProp,
-            //
-            // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
             &const_prop::ConstProp,
             &dataflow_const_prop::DataflowConstProp,
             //

tests/codegen/optimize-attr-1.rs

@@ -8,7 +8,6 @@
 
 // CHECK-LABEL: define{{.*}}i32 @nothing
 // CHECK-SAME: [[NOTHING_ATTRS:#[0-9]+]]
-// NO-OPT: ret i32 4
 // SIZE-OPT: ret i32 4
 // SPEEC-OPT: ret i32 4
 #[no_mangle]
@@ -18,7 +17,6 @@ pub fn nothing() -> i32 {
 
 // CHECK-LABEL: define{{.*}}i32 @size
 // CHECK-SAME: [[SIZE_ATTRS:#[0-9]+]]
-// NO-OPT: ret i32 6
 // SIZE-OPT: ret i32 6
 // SPEED-OPT: ret i32 6
 #[optimize(size)]
@@ -31,7 +29,6 @@ pub fn size() -> i32 {
 // NO-OPT-SAME: [[NOTHING_ATTRS]]
 // SPEED-OPT-SAME: [[NOTHING_ATTRS]]
 // SIZE-OPT-SAME: [[SPEED_ATTRS:#[0-9]+]]
-// NO-OPT: ret i32 8
 // SIZE-OPT: ret i32 8
 // SPEED-OPT: ret i32 8
 #[optimize(speed)]

tests/mir-opt/div_overflow.const_dividend.PreCodegen.after.mir

@@ -2,9 +2,15 @@
 // and is subject to change without notice. Knock yourself out.
 fn foo() -> i32 {
     let mut _0: i32;                     // return place in scope 0 at main.rs:4:19: 4:22
+    let mut _1: (i32, bool);             // in scope 0 at main.rs:5:5: 5:10
 
     bb0: {
-        _0 = const 11_i32;               // scope 0 at main.rs:5:5: 5:10
+        _1 = CheckedAdd(const 5_i32, const 6_i32); // scope 0 at main.rs:5:5: 5:10
+        assert(!move (_1.1: bool), "attempt to compute `{} + {}`, which would overflow", const 5_i32, const 6_i32) -> bb1; // scope 0 at main.rs:5:5: 5:10
+    }
+
+    bb1: {
+        _0 = move (_1.0: i32);           // scope 0 at main.rs:5:5: 5:10
         return;                          // scope 0 at main.rs:6:2: 6:2
     }
 }

tests/mir-opt/div_overflow.const_divisor.PreCodegen.after.mir

@@ -26,14 +26,6 @@ LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
    |
    = note: this note originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-note: erroneous constant used
-  --> $DIR/defaults-not-assumed-fail.rs:33:5
-   |
-LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this note originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0080`.

tests/mir-opt/div_overflow.rs

@@ -28,12 +28,6 @@ note: erroneous constant used
 LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
    |                ^^^^^^^^^^^^^
 
-note: erroneous constant used
-  --> $DIR/const-err-late.rs:19:16
-   |
-LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
-   |                ^^^^^^^^^^^^^
-
 error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.

tests/run-make/const_fn_mir/dump.mir

@@ -26,14 +26,6 @@ LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT);
    |
    = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-note: erroneous constant used
-  --> $DIR/issue-44578.rs:25:20
-   |
-LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT);
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0080`.