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Rollup merge of #104605 - RalfJung:clf_consts, r=bjorn3

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deduplicate constant evaluation in cranelift backend

The cranelift backend had two matches on `ConstantKind`, which can be avoided, and used this `eval_for_mir` that nothing else uses... this makes things more consistent with the (better-tested) LLVM backend.

I noticed this because cranelift was the only user of `eval_for_mir`. However `try_eval_for_mir` still has one other user in `eval`... the odd thing is that the interpreter has its own `eval_mir_constant` which seems to duplicate the same functionality and does not use `try_eval_for_mir`. No idea what is happening here.

r? ``@bjorn3``
Cc ``@lcnr``
This commit is contained in:
Matthias Krüger 2022-11-21 14:11:12 +01:00 committed by GitHub
commit ed22bdc18f
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3 changed files with 31 additions and 51 deletions
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58
compiler/rustc_codegen_cranelift/src/constant.rs
View File

@ -38,22 +38,8 @@ impl ConstantCx {
pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
let mut all_constants_ok = true;
for constant in &fx.mir.required_consts {
let unevaluated = match fx.monomorphize(constant.literal) {
ConstantKind::Ty(_) => unreachable!(),
ConstantKind::Unevaluated(uv, _) => uv,
ConstantKind::Val(..) => continue,
};
if let Err(err) = fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {
if eval_mir_constant(fx, constant).is_none() {
all_constants_ok = false;
match err {
ErrorHandled::Reported(_) => {
fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
}
ErrorHandled::TooGeneric => {
span_bug!(constant.span, "codegen encountered polymorphic constant: {:?}", err);
}
}
}
}
all_constants_ok
@ -80,15 +66,15 @@ pub(crate) fn codegen_tls_ref<'tcx>(
}
pub(crate) fn eval_mir_constant<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
fx: &FunctionCx<'_, '_, 'tcx>,
constant: &Constant<'tcx>,
) -> (ConstValue<'tcx>, Ty<'tcx>) {
) -> Option<(ConstValue<'tcx>, Ty<'tcx>)> {
let constant_kind = fx.monomorphize(constant.literal);
let uv = match constant_kind {
ConstantKind::Ty(const_) => match const_.kind() {
ty::ConstKind::Unevaluated(uv) => uv.expand(),
ty::ConstKind::Value(val) => {
return (fx.tcx.valtree_to_const_val((const_.ty(), val)), const_.ty());
return Some((fx.tcx.valtree_to_const_val((const_.ty(), val)), const_.ty()));
}
err => span_bug!(
constant.span,
@ -102,22 +88,31 @@ pub(crate) fn eval_mir_constant<'tcx>(
span_bug!(constant.span, "MIR constant refers to static");
}
ConstantKind::Unevaluated(uv, _) => uv,
ConstantKind::Val(val, _) => return (val, constant_kind.ty()),
ConstantKind::Val(val, _) => return Some((val, constant_kind.ty())),
};
(
fx.tcx.const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None).unwrap_or_else(|_err| {
span_bug!(constant.span, "erroneous constant not captured by required_consts");
}),
constant_kind.ty(),
)
let val = fx
.tcx
.const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None)
.map_err(|err| match err {
ErrorHandled::Reported(_) => {
fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
}
ErrorHandled::TooGeneric => {
span_bug!(constant.span, "codegen encountered polymorphic constant: {:?}", err);
}
})
.ok();
val.map(|val| (val, constant_kind.ty()))
}
pub(crate) fn codegen_constant_operand<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
constant: &Constant<'tcx>,
) -> CValue<'tcx> {
let (const_val, ty) = eval_mir_constant(fx, constant);
let (const_val, ty) = eval_mir_constant(fx, constant).unwrap_or_else(|| {
span_bug!(constant.span, "erroneous constant not captured by required_consts")
});
codegen_const_value(fx, const_val, ty)
}
@ -453,20 +448,13 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
assert!(cx.todo.is_empty(), "{:?}", cx.todo);
}
/// Used only for intrinsic implementations that need a compile-time constant
pub(crate) fn mir_operand_get_const_val<'tcx>(
fx: &FunctionCx<'_, '_, 'tcx>,
operand: &Operand<'tcx>,
) -> Option<ConstValue<'tcx>> {
match operand {
Operand::Constant(const_) => match fx.monomorphize(const_.literal) {
ConstantKind::Ty(const_) => Some(
const_.eval_for_mir(fx.tcx, ParamEnv::reveal_all()).try_to_value(fx.tcx).unwrap(),
),
ConstantKind::Val(val, _) => Some(val),
ConstantKind::Unevaluated(uv, _) => {
Some(fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), uv, None).unwrap())
}
},
Operand::Constant(const_) => Some(eval_mir_constant(fx, const_).unwrap().0),
// FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
// inside a temporary before being passed to the intrinsic requiring the const argument.
// This code tries to find a single constant defining definition of the referenced local.

9
compiler/rustc_codegen_ssa/src/mir/constant.rs
View File

@ -42,7 +42,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
};
self.cx.tcx().const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None).map_err(|err| {
self.cx.tcx().sess.span_err(constant.span, "erroneous constant encountered");
match err {
ErrorHandled::Reported(_) => {
self.cx.tcx().sess.span_err(constant.span, "erroneous constant encountered");
}
ErrorHandled::TooGeneric => {
span_bug!(constant.span, "codegen encountered polymorphic constant: {:?}", err);
}
}
err
})
}

15
compiler/rustc_middle/src/ty/consts.rs
View File

@ -1,5 +1,4 @@
use crate::mir::interpret::LitToConstInput;
use crate::mir::ConstantKind;
use crate::ty::{self, DefIdTree, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt};
use rustc_data_structures::intern::Interned;
use rustc_hir as hir;
@ -230,20 +229,6 @@ impl<'tcx> Const<'tcx> {
}
}
#[inline]
/// Tries to evaluate the constant if it is `Unevaluated` and creates a ConstValue if the
/// evaluation succeeds. If it doesn't succeed, returns the unevaluated constant.
pub fn eval_for_mir(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> ConstantKind<'tcx> {
if let Some(val) = self.kind().try_eval_for_mir(tcx, param_env) {
match val {
Ok(const_val) => ConstantKind::from_value(const_val, self.ty()),
Err(guar) => ConstantKind::Ty(tcx.const_error_with_guaranteed(self.ty(), guar)),
}
} else {
ConstantKind::Ty(self)
}
}
#[inline]
/// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {