use GlobalId in eval_to_valtree query and introduce query for valtree_to_const_val

compiler/rustc_mir_build/src/build/mod.rs

@@ -1,7 +1,9 @@
 use crate::build;
 use crate::build::expr::as_place::PlaceBuilder;
 use crate::build::scope::DropKind;
+use crate::thir::constant::parse_float;
 use crate::thir::pattern::pat_from_hir;
+use rustc_ast as ast;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -11,12 +13,15 @@ use rustc_index::vec::{Idx, IndexVec};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::middle::region;
+use rustc_middle::mir::interpret::Allocation;
+use rustc_middle::mir::interpret::{ConstValue, LitToConstError, LitToConstInput, Scalar};
 use rustc_middle::mir::*;
 use rustc_middle::thir::{BindingMode, Expr, ExprId, LintLevel, PatKind, Thir};
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeckResults};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
+use rustc_target::abi::Size;
 use rustc_target::spec::abi::Abi;
 
 use super::lints;
@@ -260,6 +265,57 @@ fn mir_build(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_
     })
 }
 
+#[instrument(skip(tcx, lit_input))]
+pub(crate) fn lit_to_mir_constant<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    lit_input: LitToConstInput<'tcx>,
+) -> Result<ConstantKind<'tcx>, LitToConstError> {
+    let LitToConstInput { lit, ty, neg } = lit_input;
+    let trunc = |n| {
+        let param_ty = ty::ParamEnv::reveal_all().and(ty);
+        let width = tcx.layout_of(param_ty).map_err(|_| LitToConstError::Reported)?.size;
+        trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
+        let result = width.truncate(n);
+        trace!("trunc result: {}", result);
+        Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
+    };
+
+    let value = match (lit, &ty.kind()) {
+        (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
+            let s = s.as_str();
+            let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes());
+            let allocation = tcx.intern_const_alloc(allocation);
+            ConstValue::Slice { data: allocation, start: 0, end: s.len() }
+        }
+        (ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _))
+            if matches!(inner_ty.kind(), ty::Slice(_)) =>
+        {
+            let allocation = Allocation::from_bytes_byte_aligned_immutable(data as &[u8]);
+            let allocation = tcx.intern_const_alloc(allocation);
+            ConstValue::Slice { data: allocation, start: 0, end: data.len() }
+        }
+        (ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => {
+            let id = tcx.allocate_bytes(data);
+            ConstValue::Scalar(Scalar::from_pointer(id.into(), &tcx))
+        }
+        (ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
+            ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
+        }
+        (ast::LitKind::Int(n, _), ty::Uint(_)) | (ast::LitKind::Int(n, _), ty::Int(_)) => {
+            trunc(if neg { (*n as i128).overflowing_neg().0 as u128 } else { *n })?
+        }
+        (ast::LitKind::Float(n, _), ty::Float(fty)) => {
+            parse_float(*n, *fty, neg).ok_or(LitToConstError::Reported)?
+        }
+        (ast::LitKind::Bool(b), ty::Bool) => ConstValue::Scalar(Scalar::from_bool(*b)),
+        (ast::LitKind::Char(c), ty::Char) => ConstValue::Scalar(Scalar::from_char(*c)),
+        (ast::LitKind::Err(_), _) => return Err(LitToConstError::Reported),
+        _ => return Err(LitToConstError::TypeError),
+    };
+
+    Ok(ConstantKind::Val(value, ty))
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // BuildMir -- walks a crate, looking for fn items and methods to build MIR from