bjoernager/rust
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Optimize some alloc_from_iter call sites.

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There's no need to collect an iterator into a `Vec`, or to call
`into_iter` at the call sites.
This commit is contained in:
Nicholas Nethercote 2023-10-03 12:20:15 +11:00
parent 816383c60d
commit a2051dd578
5 changed files with 29 additions and 38 deletions
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47
compiler/rustc_ast_lowering/src/format.rs
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@ -410,15 +410,11 @@ fn expand_format_args<'hir>(
let format_options = use_format_options.then(|| {
// Generate:
// &[format_spec_0, format_spec_1, format_spec_2]
let elements: Vec<_> = fmt
.template
.iter()
.filter_map(|piece| {
let FormatArgsPiece::Placeholder(placeholder) = piece else { return None };
Some(make_format_spec(ctx, macsp, placeholder, &mut argmap))
})
.collect();
ctx.expr_array_ref(macsp, ctx.arena.alloc_from_iter(elements))
let elements = ctx.arena.alloc_from_iter(fmt.template.iter().filter_map(|piece| {
let FormatArgsPiece::Placeholder(placeholder) = piece else { return None };
Some(make_format_spec(ctx, macsp, placeholder, &mut argmap))
}));
ctx.expr_array_ref(macsp, elements)
});
let arguments = fmt.arguments.all_args();
@ -477,10 +473,8 @@ fn expand_format_args<'hir>(
// <core::fmt::Argument>::new_debug(&arg2),
// …
// ]
let elements: Vec<_> = arguments
.iter()
.zip(argmap)
.map(|(arg, ((_, ty), placeholder_span))| {
let elements = ctx.arena.alloc_from_iter(arguments.iter().zip(argmap).map(
|(arg, ((_, ty), placeholder_span))| {
let placeholder_span =
placeholder_span.unwrap_or(arg.expr.span).with_ctxt(macsp.ctxt());
let arg_span = match arg.kind {
@ -493,9 +487,9 @@ fn expand_format_args<'hir>(
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, arg),
));
make_argument(ctx, placeholder_span, ref_arg, ty)
})
.collect();
ctx.expr_array_ref(macsp, ctx.arena.alloc_from_iter(elements))
},
));
ctx.expr_array_ref(macsp, elements)
} else {
// Generate:
// &match (&arg0, &arg1, &…) {
@ -528,19 +522,14 @@ fn expand_format_args<'hir>(
make_argument(ctx, placeholder_span, arg, ty)
},
));
let elements: Vec<_> = arguments
.iter()
.map(|arg| {
let arg_expr = ctx.lower_expr(&arg.expr);
ctx.expr(
arg.expr.span.with_ctxt(macsp.ctxt()),
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, arg_expr),
)
})
.collect();
let args_tuple = ctx
.arena
.alloc(ctx.expr(macsp, hir::ExprKind::Tup(ctx.arena.alloc_from_iter(elements))));
let elements = ctx.arena.alloc_from_iter(arguments.iter().map(|arg| {
let arg_expr = ctx.lower_expr(&arg.expr);
ctx.expr(
arg.expr.span.with_ctxt(macsp.ctxt()),
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, arg_expr),
)
}));
let args_tuple = ctx.arena.alloc(ctx.expr(macsp, hir::ExprKind::Tup(elements)));
let array = ctx.arena.alloc(ctx.expr(macsp, hir::ExprKind::Array(args)));
let match_arms = ctx.arena.alloc_from_iter([ctx.arm(args_pat, array)]);
let match_expr = ctx.arena.alloc(ctx.expr_match(