Auto merge of #96862 - oli-obk:enum_cast_mir, r=RalfJung
Change enum->int casts to not go through MIR casts. follow-up to https://github.com/rust-lang/rust/pull/96814 this simplifies all backends and even gives LLVM more information about the return value of `Rvalue::Discriminant`, enabling optimizations in more cases.
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commit
53792b9c5c
21 changed files with 238 additions and 143 deletions
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@ -204,6 +204,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
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}
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/// Obtain the actual discriminant of a value.
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#[instrument(level = "trace", skip(bx))]
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pub fn codegen_get_discr<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
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self,
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bx: &mut Bx,
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@ -420,12 +421,12 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
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}
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impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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#[instrument(level = "trace", skip(self, bx))]
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pub fn codegen_place(
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&mut self,
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bx: &mut Bx,
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place_ref: mir::PlaceRef<'tcx>,
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) -> PlaceRef<'tcx, Bx::Value> {
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debug!("codegen_place(place_ref={:?})", place_ref);
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let cx = self.cx;
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let tcx = self.cx.tcx();
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@ -12,17 +12,15 @@ use rustc_middle::ty::cast::{CastTy, IntTy};
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use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
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use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
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use rustc_span::source_map::{Span, DUMMY_SP};
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use rustc_target::abi::{Abi, Int, Variants};
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impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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#[instrument(level = "trace", skip(self, bx))]
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pub fn codegen_rvalue(
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&mut self,
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mut bx: Bx,
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dest: PlaceRef<'tcx, Bx::Value>,
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rvalue: &mir::Rvalue<'tcx>,
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) -> Bx {
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debug!("codegen_rvalue(dest.llval={:?}, rvalue={:?})", dest.llval, rvalue);
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match *rvalue {
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mir::Rvalue::Use(ref operand) => {
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let cg_operand = self.codegen_operand(&mut bx, operand);
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@ -285,74 +283,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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CastTy::from_ty(operand.layout.ty).expect("bad input type for cast");
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let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
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let ll_t_in = bx.cx().immediate_backend_type(operand.layout);
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match operand.layout.variants {
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Variants::Single { index } => {
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if let Some(discr) =
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operand.layout.ty.discriminant_for_variant(bx.tcx(), index)
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{
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let discr_layout = bx.cx().layout_of(discr.ty);
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let discr_t = bx.cx().immediate_backend_type(discr_layout);
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let discr_val = bx.cx().const_uint_big(discr_t, discr.val);
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let discr_val =
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bx.intcast(discr_val, ll_t_out, discr.ty.is_signed());
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return (
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bx,
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OperandRef {
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val: OperandValue::Immediate(discr_val),
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layout: cast,
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},
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);
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}
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}
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Variants::Multiple { .. } => {}
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}
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let llval = operand.immediate();
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let mut signed = false;
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if let Abi::Scalar(scalar) = operand.layout.abi {
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if let Int(_, s) = scalar.primitive() {
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// We use `i1` for bytes that are always `0` or `1`,
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// e.g., `#[repr(i8)] enum E { A, B }`, but we can't
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// let LLVM interpret the `i1` as signed, because
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// then `i1 1` (i.e., E::B) is effectively `i8 -1`.
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signed = !scalar.is_bool() && s;
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if !scalar.is_always_valid(bx.cx())
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&& scalar.valid_range(bx.cx()).end
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>= scalar.valid_range(bx.cx()).start
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{
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// We want `table[e as usize ± k]` to not
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// have bound checks, and this is the most
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// convenient place to put the `assume`s.
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if scalar.valid_range(bx.cx()).start > 0 {
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let enum_value_lower_bound = bx.cx().const_uint_big(
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ll_t_in,
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scalar.valid_range(bx.cx()).start,
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);
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let cmp_start = bx.icmp(
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IntPredicate::IntUGE,
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llval,
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enum_value_lower_bound,
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);
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bx.assume(cmp_start);
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}
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let enum_value_upper_bound = bx
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.cx()
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.const_uint_big(ll_t_in, scalar.valid_range(bx.cx()).end);
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let cmp_end = bx.icmp(
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IntPredicate::IntULE,
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llval,
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enum_value_upper_bound,
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);
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bx.assume(cmp_end);
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}
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}
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}
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let newval = match (r_t_in, r_t_out) {
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(CastTy::Int(_), CastTy::Int(_)) => bx.intcast(llval, ll_t_out, signed),
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(CastTy::Int(i), CastTy::Int(_)) => {
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bx.intcast(llval, ll_t_out, i.is_signed())
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}
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(CastTy::Float, CastTy::Float) => {
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let srcsz = bx.cx().float_width(ll_t_in);
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let dstsz = bx.cx().float_width(ll_t_out);
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@ -364,8 +300,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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llval
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}
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}
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(CastTy::Int(_), CastTy::Float) => {
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if signed {
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(CastTy::Int(i), CastTy::Float) => {
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if i.is_signed() {
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bx.sitofp(llval, ll_t_out)
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} else {
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bx.uitofp(llval, ll_t_out)
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@ -374,8 +310,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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(CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Ptr(_)) => {
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bx.pointercast(llval, ll_t_out)
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}
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(CastTy::Int(_), CastTy::Ptr(_)) => {
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let usize_llval = bx.intcast(llval, bx.cx().type_isize(), signed);
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(CastTy::Int(i), CastTy::Ptr(_)) => {
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let usize_llval =
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bx.intcast(llval, bx.cx().type_isize(), i.is_signed());
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bx.inttoptr(usize_llval, ll_t_out)
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}
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(CastTy::Float, CastTy::Int(IntTy::I)) => {
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@ -6,9 +6,8 @@ use crate::traits::BuilderMethods;
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use crate::traits::*;
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impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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#[instrument(level = "debug", skip(self, bx))]
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pub fn codegen_statement(&mut self, mut bx: Bx, statement: &mir::Statement<'tcx>) -> Bx {
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debug!("codegen_statement(statement={:?})", statement);
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self.set_debug_loc(&mut bx, statement.source_info);
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match statement.kind {
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mir::StatementKind::Assign(box (ref place, ref rvalue)) => {
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