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core/stmt: Remove gen_if_chained* 

Turns out it is really difficult to get lifetimes and closures right, so
let's just provide the most rudimentary if-else codegen and we can nest
them if necessary.
This commit is contained in:
David Mak 2024-04-16 16:30:18 +08:00
parent e0f440040c
commit 025b3cd02f
1 changed files with 61 additions and 194 deletions
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255
nac3core/src/codegen/stmt.rs
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@ -29,7 +29,6 @@ use nac3parser::ast::{
Constant, ExcepthandlerKind, Expr, ExprKind, Location, Stmt, StmtKind, StrRef, Constant, ExcepthandlerKind, Expr, ExprKind, Location, Stmt, StmtKind, StrRef,
}; };
use std::convert::TryFrom; use std::convert::TryFrom;
use itertools::Itertools;
/// See [`CodeGenerator::gen_var_alloc`]. /// See [`CodeGenerator::gen_var_alloc`].
pub fn gen_var<'ctx>( pub fn gen_var<'ctx>(
@ -695,173 +694,6 @@ pub fn gen_while<G: CodeGenerator>(
Ok(()) Ok(())
} }
/// Generates a C-style chained-`if` construct using lambdas, similar to the following C code:
///
/// ```c
/// T val;
/// if (ifts[0].cond()) {
/// val = ifts[0].then();
/// } else if (ifts[1].cond()) {
/// val = ifts[1].then();
/// } else if /* ... */
/// else {
/// if (else_fn) {
/// val = else_fn();
/// } else {
/// __builtin_unreachable();
/// }
/// }
/// ```
///
/// - `ifts` - A slice of tuples containing the condition and body of a branch respectively. The
/// branches will be generated in the order as appears in the slice.
/// - `else_fn` - The body to generate if no other branches evaluates to `true`. If [`None`], a call
/// to `__builtin_unreachable` will be generated instead.
pub fn gen_chained_if_expr_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn, R>(
generator: &mut G,
ctx: &mut CodeGenContext<'ctx, 'a>,
ifts: &[(CondFn, ThenFn)],
else_fn: Option<ElseFn>,
) -> Result<Option<BasicValueEnum<'ctx>>, String>
where
G: CodeGenerator + ?Sized,
CondFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>,
ThenFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>,
ElseFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>,
R: BasicValue<'ctx>,
{
assert!(!ifts.is_empty());
let current_bb = ctx.builder.get_insert_block().unwrap();
let current_fn = current_bb.get_parent().unwrap();
let end_bb = ctx.ctx.append_basic_block(current_fn, "if.end");
let vals = {
let mut vals = ifts.iter()
.map(|(cond, then)| -> Result<_, String> {
let then_bb = ctx.ctx.insert_basic_block_after(current_bb, "if.then");
let else_bb = ctx.ctx.insert_basic_block_after(current_bb, "if.else");
let cond = cond(generator, ctx)?;
assert_eq!(cond.get_type().get_bit_width(), ctx.ctx.bool_type().get_bit_width());
ctx.builder.build_conditional_branch(cond, then_bb, else_bb).unwrap();
ctx.builder.position_at_end(then_bb);
let val = then(generator, ctx)?;
if !ctx.is_terminated() {
ctx.builder.build_unconditional_branch(end_bb).unwrap();
}
ctx.builder.position_at_end(else_bb);
Ok((val, then_bb))
})
.collect::<Result<Vec<_>, _>>()?;
if let Some(else_fn) = else_fn {
let else_bb = ctx.builder.get_insert_block().unwrap();
let else_val = else_fn(generator, ctx)?;
vals.push((else_val, else_bb));
if !ctx.is_terminated() {
ctx.builder.build_unconditional_branch(end_bb).unwrap();
}
} else {
ctx.builder.build_unreachable().unwrap();
}
vals
};
ctx.builder.position_at_end(end_bb);
let phi = if vals.is_empty() {
None
} else {
let llvm_val_ty = vals.iter()
.filter_map(|(val, _)| val.as_ref().map(|v| v.as_basic_value_enum().get_type()))
.reduce(|acc, ty| {
assert_eq!(acc, ty);
acc
})
.unwrap();
let phi = ctx.builder.build_phi(llvm_val_ty, "").unwrap();
vals.into_iter()
.filter_map(|(val, bb)| val.map(|v| (v, bb)))
.for_each(|(val, bb)| phi.add_incoming(&[(&val.as_basic_value_enum(), bb)]));
Some(phi.as_basic_value())
};
Ok(phi)
}
/// Generates a C-style chained-`if` construct using lambdas, similar to the following C code:
///
/// ```c
/// if (ifts[0].cond()) {
/// ifts[0].then();
/// } else if (ifts[1].cond()) {
/// ifts[1].then();
/// } else if /* ... */
/// else {
/// if (else_fn) {
/// else_fn();
/// } else {
/// __builtin_unreachable();
/// }
/// }
/// ```
///
/// This function mainly serves as an abstraction over [`gen_chained_if_expr_callback`] when a value
/// does not need to be returned from the `if` construct.
///
/// - `ifts` - A slice of tuples containing the condition and body of a branch respectively. The
/// branches will be generated in the order as appears in the slice.
/// - `else_fn` - The body to generate if no other branches evaluates to `true`. If [`None`], a call
/// to `__builtin_unreachable` will be generated instead.
pub fn gen_chained_if_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn>(
generator: &mut G,
ctx: &mut CodeGenContext<'ctx, 'a>,
ifts: &[(CondFn, ThenFn)],
else_fn: &Option<ElseFn>,
) -> Result<(), String>
where
G: CodeGenerator + ?Sized,
CondFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>,
ThenFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>,
ElseFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>,
{
let res = gen_chained_if_expr_callback(
generator,
ctx,
ifts.iter()
.map(|(cond, then)| {
(
cond,
|generator: &mut G, ctx: &mut CodeGenContext<'ctx, 'a>| {
then(generator, ctx)?;
Ok(None::<BasicValueEnum<'ctx>>)
},
)
})
.collect_vec()
.as_slice(),
else_fn
.as_ref()
.map(|else_fn| |generator: &mut G, ctx: &mut CodeGenContext<'ctx, 'a>| {
else_fn(generator, ctx)?;
Ok(None)
}),
)?;
assert!(res.is_none());
Ok(())
}
/// Generates a C-style chained-`if` construct using lambdas, similar to the following C code: /// Generates a C-style chained-`if` construct using lambdas, similar to the following C code:
/// ///
/// ```c /// ```c
@ -872,9 +704,6 @@ pub fn gen_chained_if_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn>(
/// val = else_fn(); /// val = else_fn();
/// } /// }
/// ``` /// ```
///
/// This function mainly serves as an abstraction over [`gen_chained_if_expr_callback`] for a basic
/// `if`-`else` construct that returns a value.
pub fn gen_if_else_expr_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn, R>( pub fn gen_if_else_expr_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn, R>(
generator: &mut G, generator: &mut G,
ctx: &mut CodeGenContext<'ctx, 'a>, ctx: &mut CodeGenContext<'ctx, 'a>,
@ -884,17 +713,51 @@ pub fn gen_if_else_expr_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn, R>(
) -> Result<Option<BasicValueEnum<'ctx>>, String> ) -> Result<Option<BasicValueEnum<'ctx>>, String>
where where
G: CodeGenerator + ?Sized, G: CodeGenerator + ?Sized,
CondFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>, CondFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>,
ThenFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>, ThenFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>,
ElseFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>, ElseFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<Option<R>, String>,
R: BasicValue<'ctx>, R: BasicValue<'ctx>,
{ {
gen_chained_if_expr_callback( let current_bb = ctx.builder.get_insert_block().unwrap();
generator, let current_fn = current_bb.get_parent().unwrap();
ctx,
&[(cond_fn, then_fn)], let end_bb = ctx.ctx.append_basic_block(current_fn, "if.end");
Some(else_fn),
) let then_bb = ctx.ctx.insert_basic_block_after(current_bb, "if.then");
let else_bb = ctx.ctx.insert_basic_block_after(current_bb, "if.else");
let cond = cond_fn(generator, ctx)?;
assert_eq!(cond.get_type().get_bit_width(), ctx.ctx.bool_type().get_bit_width());
ctx.builder.build_conditional_branch(cond, then_bb, else_bb).unwrap();
ctx.builder.position_at_end(then_bb);
let then_val = then_fn(generator, ctx)?;
if !ctx.is_terminated() {
ctx.builder.build_unconditional_branch(end_bb).unwrap();
}
ctx.builder.position_at_end(else_bb);
let else_val = else_fn(generator, ctx)?;
if !ctx.is_terminated() {
ctx.builder.build_unconditional_branch(end_bb).unwrap();
}
let phi = match (then_val, else_val) {
(Some(tv), Some(ev)) => {
let tv_ty = tv.as_basic_value_enum().get_type();
assert_eq!(tv_ty, ev.as_basic_value_enum().get_type());
let phi = ctx.builder.build_phi(tv_ty, "").unwrap();
phi.add_incoming(&[(&tv, then_bb), (&ev, else_bb)]);
Some(phi.as_basic_value())
},
(Some(tv), None) => Some(tv.as_basic_value_enum()),
(None, Some(ev)) => Some(ev.as_basic_value_enum()),
(None, None) => None,
};
Ok(phi)
} }
/// Generates a C-style chained-`if` construct using lambdas, similar to the following C code: /// Generates a C-style chained-`if` construct using lambdas, similar to the following C code:
@ -903,33 +766,37 @@ pub fn gen_if_else_expr_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn, R>(
/// if (cond_fn()) { /// if (cond_fn()) {
/// then_fn(); /// then_fn();
/// } else { /// } else {
/// if (else_fn) { /// else_fn();
/// else_fn();
/// }
/// } /// }
/// ``` /// ```
///
/// This function mainly serves as an abstraction over [`gen_chained_if_expr_callback`] for a basic
/// `if`-`else` construct that does not return a value.
pub fn gen_if_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn>( pub fn gen_if_callback<'ctx, 'a, G, CondFn, ThenFn, ElseFn>(
generator: &mut G, generator: &mut G,
ctx: &mut CodeGenContext<'ctx, 'a>, ctx: &mut CodeGenContext<'ctx, 'a>,
cond_fn: CondFn, cond_fn: CondFn,
then_fn: ThenFn, then_fn: ThenFn,
else_fn: &Option<ElseFn>, else_fn: ElseFn,
) -> Result<(), String> ) -> Result<(), String>
where where
G: CodeGenerator + ?Sized, G: CodeGenerator + ?Sized,
CondFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>, CondFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<IntValue<'ctx>, String>,
ThenFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>, ThenFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>,
ElseFn: Fn(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>, ElseFn: FnOnce(&mut G, &mut CodeGenContext<'ctx, 'a>) -> Result<(), String>,
{ {
gen_chained_if_callback( gen_if_else_expr_callback(
generator, generator,
ctx, ctx,
&[(cond_fn, then_fn)], cond_fn,
else_fn, |generator, ctx| {
) then_fn(generator, ctx)?;
Ok(None::<BasicValueEnum<'ctx>>)
},
|generator, ctx| {
else_fn(generator, ctx)?;
Ok(None)
}
)?;
Ok(())
} }
/// See [`CodeGenerator::gen_if`]. /// See [`CodeGenerator::gen_if`].