compiler/rustc_codegen_ssa/src/mir/constant.rs

   1 use crate::errors;
   2 use crate::mir::operand::OperandRef;
   3 use crate::traits::*;
   4 use rustc_middle::mir;
   5 use rustc_middle::mir::interpret::{ConstValue, ErrorHandled};
   6 use rustc_middle::ty::layout::HasTyCtxt;
   7 use rustc_middle::ty::{self, Ty};
   8 use rustc_span::source_map::Span;
   9 use rustc_target::abi::Abi;
  10
  11 use super::FunctionCx;
  12
  13 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  14     pub fn eval_mir_constant_to_operand(
  15         &self,
  16         bx: &mut Bx,
  17         constant: &mir::Constant<'tcx>,
  18     ) -> Result<OperandRef<'tcx, Bx::Value>, ErrorHandled> {
  19         let val = self.eval_mir_constant(constant)?;
  20         let ty = self.monomorphize(constant.ty());
  21         Ok(OperandRef::from_const(bx, val, ty))
  22     }
  23
  24     pub fn eval_mir_constant(
  25         &self,
  26         constant: &mir::Constant<'tcx>,
  27     ) -> Result<ConstValue<'tcx>, ErrorHandled> {
  28         let ct = self.monomorphize(constant.literal);
  29         let uv = match ct {
  30             mir::ConstantKind::Ty(ct) => match ct.kind() {
  31                 ty::ConstKind::Unevaluated(uv) => uv.expand(),
  32                 ty::ConstKind::Value(val) => {
  33                     return Ok(self.cx.tcx().valtree_to_const_val((ct.ty(), val)));
  34                 }
  35                 err => span_bug!(
  36                     constant.span,
  37                     "encountered bad ConstKind after monomorphizing: {:?}",
  38                     err
  39                 ),
  40             },
  41             mir::ConstantKind::Unevaluated(uv, _) => uv,
  42             mir::ConstantKind::Val(val, _) => return Ok(val),
  43         };
  44
  45         self.cx.tcx().const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None).map_err(|err| {
  46             match err {
  47                 ErrorHandled::Reported(_) => {
  48                     self.cx.tcx().sess.emit_err(errors::ErroneousConstant { span: constant.span });
  49                 }
  50                 ErrorHandled::TooGeneric => {
  51                     self.cx
  52                         .tcx()
  53                         .sess
  54                         .diagnostic()
  55                         .emit_bug(errors::PolymorphicConstantTooGeneric { span: constant.span });
  56                 }
  57             }
  58             err
  59         })
  60     }
  61
  62     /// process constant containing SIMD shuffle indices
  63     pub fn simd_shuffle_indices(
  64         &mut self,
  65         bx: &Bx,
  66         span: Span,
  67         ty: Ty<'tcx>,
  68         constant: Result<ConstValue<'tcx>, ErrorHandled>,
  69     ) -> (Bx::Value, Ty<'tcx>) {
  70         constant
  71             .map(|val| {
  72                 let field_ty = ty.builtin_index().unwrap();
  73                 let c = mir::ConstantKind::from_value(val, ty);
  74                 let values: Vec<_> = bx
  75                     .tcx()
  76                     .destructure_mir_constant(ty::ParamEnv::reveal_all(), c)
  77                     .fields
  78                     .iter()
  79                     .map(|field| {
  80                         if let Some(prim) = field.try_to_scalar() {
  81                             let layout = bx.layout_of(field_ty);
  82                             let Abi::Scalar(scalar) = layout.abi else {
  83                                 bug!("from_const: invalid ByVal layout: {:#?}", layout);
  84                             };
  85                             bx.scalar_to_backend(prim, scalar, bx.immediate_backend_type(layout))
  86                         } else {
  87                             bug!("simd shuffle field {:?}", field)
  88                         }
  89                     })
  90                     .collect();
  91                 let llval = bx.const_struct(&values, false);
  92                 (llval, c.ty())
  93             })
  94             .unwrap_or_else(|_| {
  95                 bx.tcx().sess.emit_err(errors::ShuffleIndicesEvaluation { span });
  96                 // We've errored, so we don't have to produce working code.
  97                 let ty = self.monomorphize(ty);
  98                 let llty = bx.backend_type(bx.layout_of(ty));
  99                 (bx.const_undef(llty), ty)
 100             })
 101     }
 102 }