Lift a few limitations on ConstProp optimization pass

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -568,8 +568,17 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // NOTE: Unlike binops, negation doesn't have its own
         // checked operation, just a comparison with the minimum
         // value, so we have to check for the assert message.
-        if !bx.check_overflow() {
-            if let AssertKind::OverflowNeg(_) = *msg {
+        if !bx.cx().check_overflow() {
+            if let AssertKind::OverflowNeg(_)
+            | AssertKind::Overflow(
+                mir::BinOp::Add
+                | mir::BinOp::Sub
+                | mir::BinOp::Mul
+                | mir::BinOp::Shl
+                | mir::BinOp::Shr,
+                ..,
+            ) = *msg
+            {
                 const_cond = Some(expected);
             }
         }

tests/mir-opt/const_prop/bad_op_div_by_zero.main.ConstProp.diff

@@ -24,9 +24,10 @@
           StorageLive(_3);                 // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:18: +2:19
 -         _3 = _1;                         // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:18: +2:19
 -         _4 = Eq(_3, const 0_i32);        // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:14: +2:19
+-         assert(!move _4, "attempt to divide `{}` by zero", const 1_i32) -> bb1; // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:14: +2:19
 +         _3 = const 0_i32;                // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:18: +2:19
 +         _4 = const true;                 // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:14: +2:19
-          assert(!move _4, "attempt to divide `{}` by zero", const 1_i32) -> bb1; // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:14: +2:19
++         assert(!const true, "attempt to divide `{}` by zero", const 1_i32) -> bb1; // scope 1 at $DIR/bad_op_div_by_zero.rs:+2:14: +2:19
       }
 
       bb1: {

tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.diff

@@ -8,8 +8,9 @@
 
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
-          _1 = const _;                    // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
+-         _1 = const _;                    // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
 -         switchInt(move _1) -> [0: bb2, otherwise: bb1]; // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
++         _1 = const false;                // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
 +         switchInt(const false) -> [0: bb2, otherwise: bb1]; // scope 0 at $DIR/control_flow_simplification.rs:+1:8: +1:21
       }
 

tests/mir-opt/const_prop/slice_len.main.ConstProp.32bit.diff

@@ -28,17 +28,15 @@
           StorageDead(_3);                 // scope 0 at $DIR/slice_len.rs:+1:18: +1:19
           StorageLive(_6);                 // scope 0 at $DIR/slice_len.rs:+1:31: +1:32
           _6 = const 1_usize;              // scope 0 at $DIR/slice_len.rs:+1:31: +1:32
--         _7 = Len((*_2));                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
+          _7 = const 3_usize;              // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 -         _8 = Lt(_6, _7);                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 -         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, _6) -> bb1; // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
-+         _7 = const 3_usize;              // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 +         _8 = const true;                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 +         assert(const true, "index out of bounds: the length is {} but the index is {}", move _7, _6) -> bb1; // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
       }
 
       bb1: {
--         _1 = (*_2)[_6];                  // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
-+         _1 = const 2_u32;                // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
+          _1 = (*_2)[_6];                  // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
           StorageDead(_6);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34
           StorageDead(_4);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34
           StorageDead(_2);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34

tests/mir-opt/const_prop/slice_len.main.ConstProp.64bit.diff

@@ -28,17 +28,15 @@
           StorageDead(_3);                 // scope 0 at $DIR/slice_len.rs:+1:18: +1:19
           StorageLive(_6);                 // scope 0 at $DIR/slice_len.rs:+1:31: +1:32
           _6 = const 1_usize;              // scope 0 at $DIR/slice_len.rs:+1:31: +1:32
--         _7 = Len((*_2));                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
+          _7 = const 3_usize;              // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 -         _8 = Lt(_6, _7);                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 -         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, _6) -> bb1; // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
-+         _7 = const 3_usize;              // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 +         _8 = const true;                 // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
 +         assert(const true, "index out of bounds: the length is {} but the index is {}", move _7, _6) -> bb1; // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
       }
 
       bb1: {
--         _1 = (*_2)[_6];                  // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
-+         _1 = const 2_u32;                // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
+          _1 = (*_2)[_6];                  // scope 0 at $DIR/slice_len.rs:+1:5: +1:33
           StorageDead(_6);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34
           StorageDead(_4);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34
           StorageDead(_2);                 // scope 0 at $DIR/slice_len.rs:+1:33: +1:34

tests/mir-opt/const_prop/slice_len.rs

@@ -1,5 +1,5 @@
 // unit-test: ConstProp
-// compile-flags: -Zmir-enable-passes=+InstCombine
+// compile-flags: -Zmir-enable-passes=+InstCombine,+NormalizeArrayLen
 // EMIT_MIR_FOR_EACH_BIT_WIDTH
 
 // EMIT_MIR slice_len.main.ConstProp.diff

tests/mir-opt/dataflow-const-prop/inherit_overflow.main.DataflowConstProp.diff

@@ -18,8 +18,8 @@
       bb0: {
           _1 = const u8::MAX;              // scope 0 at $DIR/inherit_overflow.rs:+3:13: +3:47
           _2 = const 1_u8;                 // scope 0 at $DIR/inherit_overflow.rs:+3:13: +3:47
-          _5 = CheckedAdd(const u8::MAX, const 1_u8); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
-          assert(!move (_5.1: bool), "attempt to compute `{} + {}`, which would overflow", const u8::MAX, const 1_u8) -> bb1; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
+          _5 = const (0_u8, true);         // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
+          assert(!const true, "attempt to compute `{} + {}`, which would overflow", const u8::MAX, const 1_u8) -> bb1; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
       }
 
       bb1: {

tests/ui/consts/const-eval/issue-50814.rs

@@ -14,11 +14,13 @@ struct Sum<A, B>(A, B);
 impl<A: Unsigned, B: Unsigned> Unsigned for Sum<A, B> {
     const MAX: u8 = A::MAX + B::MAX;
     //~^ ERROR evaluation of `<Sum<U8, U8> as Unsigned>::MAX` failed
+    //~| ERROR evaluation of `<Sum<U8, U8> as Unsigned>::MAX` failed
 }
 
 fn foo<T>(_: T) -> &'static u8 {
     &Sum::<U8, U8>::MAX
     //~^ constant
+    //~| constant
 }
 
 fn main() {

tests/ui/consts/const-eval/issue-50814.stderr

@@ -5,17 +5,35 @@ LL |     const MAX: u8 = A::MAX + B::MAX;
    |                     ^^^^^^^^^^^^^^^ attempt to compute `u8::MAX + u8::MAX`, which would overflow
 
 note: erroneous constant used
-  --> $DIR/issue-50814.rs:20:6
+  --> $DIR/issue-50814.rs:21:6
+   |
+LL |     &Sum::<U8, U8>::MAX
+   |      ^^^^^^^^^^^^^^^^^^
+
+note: erroneous constant used
+  --> $DIR/issue-50814.rs:21:5
+   |
+LL |     &Sum::<U8, U8>::MAX
+   |     ^^^^^^^^^^^^^^^^^^^
+
+error[E0080]: evaluation of `<Sum<U8, U8> as Unsigned>::MAX` failed
+  --> $DIR/issue-50814.rs:15:21
+   |
+LL |     const MAX: u8 = A::MAX + B::MAX;
+   |                     ^^^^^^^^^^^^^^^ attempt to compute `u8::MAX + u8::MAX`, which would overflow
+
+note: erroneous constant used
+  --> $DIR/issue-50814.rs:21:6
    |
 LL |     &Sum::<U8, U8>::MAX
    |      ^^^^^^^^^^^^^^^^^^
 
 note: the above error was encountered while instantiating `fn foo::<i32>`
-  --> $DIR/issue-50814.rs:25:5
+  --> $DIR/issue-50814.rs:27:5
    |
 LL |     foo(0);
    |     ^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.