Merging upstream version 1.75.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 84 insertions, 5 deletions

diff --git a/compiler/rustc_middle/src/mir/consts.rs b/compiler/rustc_middle/src/mir/consts.rs
index 7c8a57b84..a9d09709e 100644
--- a/compiler/rustc_middle/src/mir/consts.rs
+++ b/compiler/rustc_middle/src/mir/consts.rs
@@ -3,6 +3,7 @@ use std::fmt::{self, Debug, Display, Formatter};
 use rustc_hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{self as hir};
+use rustc_session::RemapFileNameExt;
 use rustc_span::Span;
 use rustc_target::abi::{HasDataLayout, Size};
 
@@ -172,6 +173,24 @@ impl<'tcx> ConstValue<'tcx> {
         let end = end.try_into().unwrap();
         Some(data.inner().inspect_with_uninit_and_ptr_outside_interpreter(start..end))
     }
+
+    /// Check if a constant may contain provenance information. This is used by MIR opts.
+    /// Can return `true` even if there is no provenance.
+    pub fn may_have_provenance(&self, tcx: TyCtxt<'tcx>, size: Size) -> bool {
+        match *self {
+            ConstValue::ZeroSized | ConstValue::Scalar(Scalar::Int(_)) => return false,
+            ConstValue::Scalar(Scalar::Ptr(..)) => return true,
+            // It's hard to find out the part of the allocation we point to;
+            // just conservatively check everything.
+            ConstValue::Slice { data, meta: _ } => !data.inner().provenance().ptrs().is_empty(),
+            ConstValue::Indirect { alloc_id, offset } => !tcx
+                .global_alloc(alloc_id)
+                .unwrap_memory()
+                .inner()
+                .provenance()
+                .range_empty(super::AllocRange::from(offset..offset + size), &tcx),
+        }
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -213,10 +232,10 @@ impl<'tcx> Const<'tcx> {
     pub fn try_to_scalar(self) -> Option<Scalar> {
         match self {
             Const::Ty(c) => match c.kind() {
-                ty::ConstKind::Value(valtree) => match valtree {
-                    ty::ValTree::Leaf(scalar_int) => Some(Scalar::Int(scalar_int)),
-                    ty::ValTree::Branch(_) => None,
-                },
+                ty::ConstKind::Value(valtree) if c.ty().is_primitive() => {
+                    // A valtree of a type where leaves directly represent the scalar const value.
+                    Some(valtree.unwrap_leaf().into())
+                }
                 _ => None,
             },
             Const::Val(val, _) => val.try_to_scalar(),
@@ -279,7 +298,16 @@ impl<'tcx> Const<'tcx> {
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> Option<Scalar> {
-        self.eval(tcx, param_env, None).ok()?.try_to_scalar()
+        match self {
+            Const::Ty(c) if c.ty().is_primitive() => {
+                // Avoid the `valtree_to_const_val` query. Can only be done on primitive types that
+                // are valtree leaves, and *not* on references. (References should return the
+                // pointer here, which valtrees don't represent.)
+                let val = c.eval(tcx, param_env, None).ok()?;
+                Some(val.unwrap_leaf().into())
+            }
+            _ => self.eval(tcx, param_env, None).ok()?.try_to_scalar(),
+        }
     }
 
     #[inline]
@@ -476,6 +504,40 @@ impl<'tcx> Const<'tcx> {
             _ => Self::Ty(c),
         }
     }
+
+    /// Return true if any evaluation of this constant always returns the same value,
+    /// taking into account even pointer identity tests.
+    pub fn is_deterministic(&self) -> bool {
+        // Some constants may generate fresh allocations for pointers they contain,
+        // so using the same constant twice can yield two different results:
+        // - valtrees purposefully generate new allocations
+        // - ConstValue::Slice also generate new allocations
+        match self {
+            Const::Ty(c) => match c.kind() {
+                ty::ConstKind::Param(..) => true,
+                // A valtree may be a reference. Valtree references correspond to a
+                // different allocation each time they are evaluated. Valtrees for primitive
+                // types are fine though.
+                ty::ConstKind::Value(_) => c.ty().is_primitive(),
+                ty::ConstKind::Unevaluated(..) | ty::ConstKind::Expr(..) => false,
+                // This can happen if evaluation of a constant failed. The result does not matter
+                // much since compilation is doomed.
+                ty::ConstKind::Error(..) => false,
+                // Should not appear in runtime MIR.
+                ty::ConstKind::Infer(..)
+                | ty::ConstKind::Bound(..)
+                | ty::ConstKind::Placeholder(..) => bug!(),
+            },
+            Const::Unevaluated(..) => false,
+            // If the same slice appears twice in the MIR, we cannot guarantee that we will
+            // give the same `AllocId` to the data.
+            Const::Val(ConstValue::Slice { .. }, _) => false,
+            Const::Val(
+                ConstValue::ZeroSized | ConstValue::Scalar(_) | ConstValue::Indirect { .. },
+                _,
+            ) => true,
+        }
+    }
 }
 
 /// An unevaluated (potentially generic) constant used in MIR.
@@ -520,3 +582,20 @@ impl<'tcx> Display for Const<'tcx> {
         }
     }
 }
+
+///////////////////////////////////////////////////////////////////////////
+/// Const-related utilities
+
+impl<'tcx> TyCtxt<'tcx> {
+    pub fn span_as_caller_location(self, span: Span) -> ConstValue<'tcx> {
+        let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
+        let caller = self.sess.source_map().lookup_char_pos(topmost.lo());
+        self.const_caller_location(
+            rustc_span::symbol::Symbol::intern(
+                &caller.file.name.for_codegen(&self.sess).to_string_lossy(),
+            ),
+            caller.line as u32,
+            caller.col_display as u32 + 1,
+        )
+    }
+}