compiler/rustc_codegen_ssa/src/mir/constant.rs

   1 use crate::mir::operand::OperandRef;
   2 use crate::traits::*;
   3 use rustc_middle::mir;
   4 use rustc_middle::mir::interpret::{ConstValue, ErrorHandled};
   5 use rustc_middle::ty::layout::HasTyCtxt;
   6 use rustc_middle::ty::{self, Ty};
   7 use rustc_span::source_map::Span;
   8 use rustc_target::abi::Abi;
   9
  10 use super::FunctionCx;
  11
  12 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  13     pub fn eval_mir_constant_to_operand(
  14         &self,
  15         bx: &mut Bx,
  16         constant: &mir::Constant<'tcx>,
  17     ) -> Result<OperandRef<'tcx, Bx::Value>, ErrorHandled> {
  18         let val = self.eval_mir_constant(constant)?;
  19         let ty = self.monomorphize(constant.ty());
  20         Ok(OperandRef::from_const(bx, val, ty))
  21     }
  22
  23     pub fn eval_mir_constant(
  24         &self,
  25         constant: &mir::Constant<'tcx>,
  26     ) -> Result<ConstValue<'tcx>, ErrorHandled> {
  27         let ct = self.monomorphize(constant.literal);
  28         let uv = match ct {
  29             mir::ConstantKind::Ty(ct) => match ct.kind() {
  30                 ty::ConstKind::Unevaluated(uv) => uv.expand(),
  31                 ty::ConstKind::Value(val) => {
  32                     return Ok(self.cx.tcx().valtree_to_const_val((ct.ty(), val)));
  33                 }
  34                 err => span_bug!(
  35                     constant.span,
  36                     "encountered bad ConstKind after monomorphizing: {:?}",
  37                     err
  38                 ),
  39             },
  40             mir::ConstantKind::Unevaluated(uv, _) => uv,
  41             mir::ConstantKind::Val(val, _) => return Ok(val),
  42         };
  43
  44         self.cx.tcx().const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None).map_err(|err| {
  45             self.cx.tcx().sess.span_err(constant.span, "erroneous constant encountered");
  46             err
  47         })
  48     }
  49
  50     /// process constant containing SIMD shuffle indices
  51     pub fn simd_shuffle_indices(
  52         &mut self,
  53         bx: &Bx,
  54         span: Span,
  55         ty: Ty<'tcx>,
  56         constant: Result<ConstValue<'tcx>, ErrorHandled>,
  57     ) -> (Bx::Value, Ty<'tcx>) {
  58         constant
  59             .map(|val| {
  60                 let field_ty = ty.builtin_index().unwrap();
  61                 let c = mir::ConstantKind::from_value(val, ty);
  62                 let values: Vec<_> = bx
  63                     .tcx()
  64                     .destructure_mir_constant(ty::ParamEnv::reveal_all(), c)
  65                     .fields
  66                     .iter()
  67                     .map(|field| {
  68                         if let Some(prim) = field.try_to_scalar() {
  69                             let layout = bx.layout_of(field_ty);
  70                             let Abi::Scalar(scalar) = layout.abi else {
  71                                 bug!("from_const: invalid ByVal layout: {:#?}", layout);
  72                             };
  73                             bx.scalar_to_backend(prim, scalar, bx.immediate_backend_type(layout))
  74                         } else {
  75                             bug!("simd shuffle field {:?}", field)
  76                         }
  77                     })
  78                     .collect();
  79                 let llval = bx.const_struct(&values, false);
  80                 (llval, c.ty())
  81             })
  82             .unwrap_or_else(|_| {
  83                 bx.tcx().sess.span_err(span, "could not evaluate shuffle_indices at compile time");
  84                 // We've errored, so we don't have to produce working code.
  85                 let ty = self.monomorphize(ty);
  86                 let llty = bx.backend_type(bx.layout_of(ty));
  87                 (bx.const_undef(llty), ty)
  88             })
  89     }
  90 }