Always propagate into operands.

Author: cjgillot

compiler/rustc_mir_transform/src/const_prop.rs

@@ -810,12 +810,7 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
 
     fn visit_operand(&mut self, operand: &mut Operand<'tcx>, location: Location) {
         self.super_operand(operand, location);
-
-        // Only const prop copies and moves on `mir_opt_level=3` as doing so
-        // currently slightly increases compile time in some cases.
-        if self.tcx.sess.mir_opt_level() >= 3 {
-            self.propagate_operand(operand)
-        }
+        self.propagate_operand(operand)
     }
 
     fn process_projection_elem(

tests/mir-opt/const_prop/aggregate.main.ConstProp.panic-abort.diff

@@ -26,8 +26,9 @@
           StorageLive(_4);
           StorageLive(_5);
 -         _5 = _1;
+-         _4 = foo(move _5) -> [return: bb1, unwind unreachable];
 +         _5 = const 1_u8;
-          _4 = foo(move _5) -> [return: bb1, unwind unreachable];
++         _4 = foo(const 1_u8) -> [return: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/const_prop/aggregate.main.ConstProp.panic-unwind.diff

@@ -26,8 +26,9 @@
           StorageLive(_4);
           StorageLive(_5);
 -         _5 = _1;
+-         _4 = foo(move _5) -> [return: bb1, unwind continue];
 +         _5 = const 1_u8;
-          _4 = foo(move _5) -> [return: bb1, unwind continue];
++         _4 = foo(const 1_u8) -> [return: bb1, unwind continue];
       }
 
       bb1: {

tests/mir-opt/const_prop/aggregate.main.PreCodegen.after.panic-abort.mir

@@ -23,7 +23,7 @@ fn main() -> () {
         StorageLive(_4);
         StorageLive(_5);
         _5 = const 1_u8;
-        _4 = foo(move _5) -> [return: bb1, unwind unreachable];
+        _4 = foo(const 1_u8) -> [return: bb1, unwind unreachable];
     }
 
     bb1: {

tests/mir-opt/const_prop/aggregate.main.PreCodegen.after.panic-unwind.mir

@@ -23,7 +23,7 @@ fn main() -> () {
         StorageLive(_4);
         StorageLive(_5);
         _5 = const 1_u8;
-        _4 = foo(move _5) -> [return: bb1, unwind continue];
+        _4 = foo(const 1_u8) -> [return: bb1, unwind continue];
     }
 
     bb1: {

tests/mir-opt/const_prop/array_index.main.ConstProp.32bit.panic-abort.diff

@@ -23,7 +23,7 @@
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
 +         _4 = const 4_usize;
 +         _5 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/const_prop/array_index.main.ConstProp.32bit.panic-unwind.diff

@@ -23,7 +23,7 @@
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
 +         _4 = const 4_usize;
 +         _5 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind continue];
       }
 
       bb1: {

tests/mir-opt/const_prop/array_index.main.ConstProp.64bit.panic-abort.diff

@@ -23,7 +23,7 @@
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
 +         _4 = const 4_usize;
 +         _5 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind unreachable];
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/const_prop/array_index.main.ConstProp.64bit.panic-unwind.diff

@@ -23,7 +23,7 @@
 -         assert(move _5, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
 +         _4 = const 4_usize;
 +         _5 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", move _4, _3) -> [success: bb1, unwind continue];
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 4_usize, const 2_usize) -> [success: bb1, unwind continue];
       }
 
       bb1: {

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

@@ -38,11 +38,12 @@
 +         _5 = const false;
 +         _6 = const false;
 +         _7 = const false;
-+         assert(!const false, "attempt to compute `{} / {}`, which would overflow", const 1_i32, _3) -> [success: bb2, unwind unreachable];
++         assert(!const false, "attempt to compute `{} / {}`, which would overflow", const 1_i32, const 0_i32) -> [success: bb2, unwind unreachable];
       }
 
       bb2: {
-          _2 = Div(const 1_i32, move _3);
+-         _2 = Div(const 1_i32, move _3);
++         _2 = Div(const 1_i32, const 0_i32);
           StorageDead(_3);
           _0 = const ();
           StorageDead(_2);