compiler/rustc_codegen_ssa/src/mir/statement.rs

   1 use rustc_middle::mir;
   2 use rustc_middle::mir::NonDivergingIntrinsic;
   3
   4 use super::FunctionCx;
   5 use super::LocalRef;
   6 use crate::traits::BuilderMethods;
   7 use crate::traits::*;
   8
   9 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  10     #[instrument(level = "debug", skip(self, bx))]
  11     pub fn codegen_statement(&mut self, mut bx: Bx, statement: &mir::Statement<'tcx>) -> Bx {
  12         self.set_debug_loc(&mut bx, statement.source_info);
  13         match statement.kind {
  14             mir::StatementKind::Assign(box (ref place, ref rvalue)) => {
  15                 if let Some(index) = place.as_local() {
  16                     match self.locals[index] {
  17                         LocalRef::Place(cg_dest) => self.codegen_rvalue(bx, cg_dest, rvalue),
  18                         LocalRef::UnsizedPlace(cg_indirect_dest) => {
  19                             self.codegen_rvalue_unsized(bx, cg_indirect_dest, rvalue)
  20                         }
  21                         LocalRef::Operand(None) => {
  22                             let (mut bx, operand) = self.codegen_rvalue_operand(bx, rvalue);
  23                             self.locals[index] = LocalRef::Operand(Some(operand));
  24                             self.debug_introduce_local(&mut bx, index);
  25                             bx
  26                         }
  27                         LocalRef::Operand(Some(op)) => {
  28                             if !op.layout.is_zst() {
  29                                 span_bug!(
  30                                     statement.source_info.span,
  31                                     "operand {:?} already assigned",
  32                                     rvalue
  33                                 );
  34                             }
  35
  36                             // If the type is zero-sized, it's already been set here,
  37                             // but we still need to make sure we codegen the operand
  38                             self.codegen_rvalue_operand(bx, rvalue).0
  39                         }
  40                     }
  41                 } else {
  42                     let cg_dest = self.codegen_place(&mut bx, place.as_ref());
  43                     self.codegen_rvalue(bx, cg_dest, rvalue)
  44                 }
  45             }
  46             mir::StatementKind::SetDiscriminant { box ref place, variant_index } => {
  47                 self.codegen_place(&mut bx, place.as_ref())
  48                     .codegen_set_discr(&mut bx, variant_index);
  49                 bx
  50             }
  51             mir::StatementKind::Deinit(..) => {
  52                 // For now, don't codegen this to anything. In the future it may be worth
  53                 // experimenting with what kind of information we can emit to LLVM without hurting
  54                 // perf here
  55                 bx
  56             }
  57             mir::StatementKind::StorageLive(local) => {
  58                 if let LocalRef::Place(cg_place) = self.locals[local] {
  59                     cg_place.storage_live(&mut bx);
  60                 } else if let LocalRef::UnsizedPlace(cg_indirect_place) = self.locals[local] {
  61                     cg_indirect_place.storage_live(&mut bx);
  62                 }
  63                 bx
  64             }
  65             mir::StatementKind::StorageDead(local) => {
  66                 if let LocalRef::Place(cg_place) = self.locals[local] {
  67                     cg_place.storage_dead(&mut bx);
  68                 } else if let LocalRef::UnsizedPlace(cg_indirect_place) = self.locals[local] {
  69                     cg_indirect_place.storage_dead(&mut bx);
  70                 }
  71                 bx
  72             }
  73             mir::StatementKind::Coverage(box ref coverage) => {
  74                 self.codegen_coverage(&mut bx, coverage.clone(), statement.source_info.scope);
  75                 bx
  76             }
  77             mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(ref op)) => {
  78                 let op_val = self.codegen_operand(&mut bx, op);
  79                 bx.assume(op_val.immediate());
  80                 bx
  81             }
  82             mir::StatementKind::Intrinsic(box NonDivergingIntrinsic::CopyNonOverlapping(
  83                 mir::CopyNonOverlapping { ref count, ref src, ref dst },
  84             )) => {
  85                 let dst_val = self.codegen_operand(&mut bx, dst);
  86                 let src_val = self.codegen_operand(&mut bx, src);
  87                 let count = self.codegen_operand(&mut bx, count).immediate();
  88                 let pointee_layout = dst_val
  89                     .layout
  90                     .pointee_info_at(&bx, rustc_target::abi::Size::ZERO)
  91                     .expect("Expected pointer");
  92                 let bytes = bx.mul(count, bx.const_usize(pointee_layout.size.bytes()));
  93
  94                 let align = pointee_layout.align;
  95                 let dst = dst_val.immediate();
  96                 let src = src_val.immediate();
  97                 bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty());
  98                 bx
  99             }
 100             mir::StatementKind::FakeRead(..)
 101             | mir::StatementKind::Retag { .. }
 102             | mir::StatementKind::AscribeUserType(..)
 103             | mir::StatementKind::Nop => bx,
 104         }
 105     }
 106 }