Lower the assume intrinsic to a MIR statement

4 files changed, 13 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index f3676604bb0..48eb292c490 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1377,6 +1377,7 @@ impl Debug for Statement<'_> {
             }) => {
                 write!(fmt, "copy_nonoverlapping(src={:?}, dst={:?}, count={:?})", src, dst, count)
             }
+            Assume(box ref cond) => write!(fmt, "assume({:?})", cond),
             Nop => write!(fmt, "nop"),
         }
     }
diff --git a/compiler/rustc_middle/src/mir/spanview.rs b/compiler/rustc_middle/src/mir/spanview.rs
index 6e64a3b80c1..cb5adee6910 100644
--- a/compiler/rustc_middle/src/mir/spanview.rs
+++ b/compiler/rustc_middle/src/mir/spanview.rs
@@ -250,6 +250,7 @@ pub fn statement_kind_name(statement: &Statement<'_>) -> &'static str {
         AscribeUserType(..) => "AscribeUserType",
         Coverage(..) => "Coverage",
         CopyNonOverlapping(..) => "CopyNonOverlapping",
+        Assume(..) => "Assume",
         Nop => "Nop",
     }
 }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index d7b9d59eced..01ac2456a13 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -342,6 +342,14 @@ pub enum StatementKind<'tcx> {
     /// I vaguely remember Ralf saying somewhere that he thought it should not be.
     CopyNonOverlapping(Box<CopyNonOverlapping<'tcx>>),
 
+    /// Denotes a call to the intrinsic function `assume`.
+    ///
+    /// The operand must be a boolean. Optimizers may use the value of the boolean to backtrack its
+    /// computation to infer information about other variables. So if the boolean came from a
+    /// `x < y` operation, subsequent operations on `x` and `y` could elide various bound checks.
+    /// If the argument is `false`, this operation is equivalent to `TerminatorKind::Unreachable`.
+    Assume(Box<Operand<'tcx>>),
+
     /// No-op. Useful for deleting instructions without affecting statement indices.
     Nop,
 }
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 7bd65f42e3f..a0273e78b8f 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -434,6 +434,9 @@ macro_rules! make_mir_visitor {
                       self.visit_operand(dst, location);
                       self.visit_operand(count, location)
                     }
+                    StatementKind::Assume(box ref $($mutability)? val) => {
+                        self.visit_operand(val, location)
+                    }
                     StatementKind::Nop => {}
                 }
             }