Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

deduplicate constant evaluation in cranelift backend #104605

Merged
merged 1 commit into from
Nov 21, 2022
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
58 changes: 23 additions & 35 deletions compiler/rustc_codegen_cranelift/src/constant.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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,
Expand All @@ -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)
}
Expand Down Expand Up @@ -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.
Expand Down
9 changes: 8 additions & 1 deletion compiler/rustc_codegen_ssa/src/mir/constant.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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
})
}
Expand Down
15 changes: 0 additions & 15 deletions compiler/rustc_middle/src/ty/consts.rs
Original file line number Diff line number Diff line change
@@ -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;
Expand Down Expand Up @@ -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 {
Expand Down