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mir-opt: Do not create storage marks for temporary locals

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This commit is contained in:
dianqk 2025-05-24 15:36:06 +08:00
parent 145d2266d9
commit 8c7faa6ed1
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7 changed files with 8 additions and 69 deletions
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48
compiler/rustc_mir_transform/src/early_otherwise_branch.rs
View file

@ -128,28 +128,20 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
let mut patch = MirPatch::new(body);
let (second_discriminant_temp, second_operand) = if opt_data.need_hoist_discriminant {
let second_operand = if opt_data.need_hoist_discriminant {
// create temp to store second discriminant in, `_s` in example above
let second_discriminant_temp =
patch.new_temp(opt_data.child_ty, opt_data.child_source.span);
patch.add_statement(
parent_end,
StatementKind::StorageLive(second_discriminant_temp),
);
// create assignment of discriminant
patch.add_assign(
parent_end,
Place::from(second_discriminant_temp),
Rvalue::Discriminant(opt_data.child_place),
);
(
Some(second_discriminant_temp),
Operand::Move(Place::from(second_discriminant_temp)),
)
Operand::Move(Place::from(second_discriminant_temp))
} else {
(None, Operand::Copy(opt_data.child_place))
Operand::Copy(opt_data.child_place)
};
// create temp to store inequality comparison between the two discriminants, `_t` in
@ -157,7 +149,6 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
let nequal = BinOp::Ne;
let comp_res_type = nequal.ty(tcx, parent_ty, opt_data.child_ty);
let comp_temp = patch.new_temp(comp_res_type, opt_data.child_source.span);
patch.add_statement(parent_end, StatementKind::StorageLive(comp_temp));
// create inequality comparison
let comp_rvalue =
@ -193,42 +184,13 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
let eq_bb = patch.new_block(eq_switch);
// Jump to it on the basis of the inequality comparison
let mut true_case = opt_data.destination;
let mut false_case = eq_bb;
// Create an indirect BB to add `StorageDead` If the jump target is itself.
for bb in [&mut false_case, &mut true_case].into_iter() {
if *bb == parent {
*bb = patch.new_block(BasicBlockData::new(
Some(Terminator {
kind: TerminatorKind::Goto { target: parent },
source_info: bbs[parent].terminator().source_info,
}),
bbs[parent].is_cleanup,
));
}
}
let true_case = opt_data.destination;
let false_case = eq_bb;
patch.patch_terminator(
parent,
TerminatorKind::if_(Operand::Move(Place::from(comp_temp)), true_case, false_case),
);
if let Some(second_discriminant_temp) = second_discriminant_temp {
// generate StorageDead for the second_discriminant_temp not in use anymore
patch.add_statement(
parent_end,
StatementKind::StorageDead(second_discriminant_temp),
);
}
// Generate a StorageDead for comp_temp in each of the targets, since we moved it into
// the switch
for bb in [false_case, true_case].into_iter() {
patch.add_statement(
Location { block: bb, statement_index: 0 },
StatementKind::StorageDead(comp_temp),
);
}
patch.apply(body);
}

5
tests/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff
View file

@ -32,16 +32,12 @@
StorageDead(_4);
_9 = discriminant((_3.0: Option2<u32>));
- switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
+ StorageLive(_12);
+ _12 = discriminant((_3.1: Option2<bool>));
+ StorageLive(_13);
+ _13 = Ne(copy _9, move _12);
+ StorageDead(_12);
+ switchInt(move _13) -> [0: bb7, otherwise: bb1];
}
bb1: {
+ StorageDead(_13);
_0 = const 1_u32;
- goto -> bb8;
+ goto -> bb5;
@ -100,7 +96,6 @@
+ }
+
+ bb7: {
+ StorageDead(_13);
+ switchInt(copy _9) -> [0: bb4, 1: bb3, 2: bb2, otherwise: bb6];
}
}

5
tests/mir-opt/early_otherwise_branch.opt4.EarlyOtherwiseBranch.diff
View file

@ -32,16 +32,12 @@
StorageDead(_4);
_9 = discriminant((_3.0: Option2<u32>));
- switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
+ StorageLive(_12);
+ _12 = discriminant((_3.1: Option2<u32>));
+ StorageLive(_13);
+ _13 = Ne(copy _9, move _12);
+ StorageDead(_12);
+ switchInt(move _13) -> [0: bb7, otherwise: bb1];
}
bb1: {
+ StorageDead(_13);
_0 = const 1_u32;
- goto -> bb8;
+ goto -> bb5;
@ -100,7 +96,6 @@
+ }
+
+ bb7: {
+ StorageDead(_13);
+ switchInt(copy _9) -> [0: bb4, 1: bb3, 2: bb2, otherwise: bb6];
}
}

3
tests/mir-opt/early_otherwise_branch.opt5.EarlyOtherwiseBranch.diff
View file

@ -20,13 +20,11 @@
StorageDead(_5);
StorageDead(_4);
- switchInt(copy (_3.0: u32)) -> [1: bb2, 2: bb3, 3: bb4, otherwise: bb1];
+ StorageLive(_6);
+ _6 = Ne(copy (_3.0: u32), copy (_3.1: u32));
+ switchInt(move _6) -> [0: bb6, otherwise: bb1];
}
bb1: {
+ StorageDead(_6);
_0 = const 0_u32;
- goto -> bb8;
+ goto -> bb5;
@ -70,7 +68,6 @@
- bb8: {
- StorageDead(_3);
- return;
+ StorageDead(_6);
+ switchInt(copy (_3.0: u32)) -> [1: bb4, 2: bb3, 3: bb2, otherwise: bb1];
}
}

2
tests/mir-opt/early_otherwise_branch.rs
View file

@ -132,6 +132,8 @@ fn opt5_failed_type(x: u32, y: u64) -> u32 {
#[custom_mir(dialect = "runtime")]
fn target_self(val: i32) {
// CHECK-LABEL: fn target_self(
// CHECK: Ne(
// CHECK-NEXT: switchInt
mir! {
{
Goto(bb1)

9
tests/mir-opt/early_otherwise_branch.target_self.EarlyOtherwiseBranch.diff
View file

@ -11,9 +11,8 @@
bb1: {
- switchInt(copy _1) -> [0: bb2, otherwise: bb1];
+ StorageLive(_2);
+ _2 = Ne(copy _1, copy _1);
+ switchInt(move _2) -> [0: bb3, otherwise: bb4];
+ switchInt(move _2) -> [0: bb3, otherwise: bb1];
}
bb2: {
@ -23,13 +22,7 @@
bb3: {
- return;
+ StorageDead(_2);
+ switchInt(copy _1) -> [0: bb2, otherwise: bb1];
+ }
+
+ bb4: {
+ StorageDead(_2);
+ goto -> bb1;
}
}

5
tests/mir-opt/early_otherwise_branch_3_element_tuple.opt2.EarlyOtherwiseBranch.diff
View file

@ -42,16 +42,12 @@
StorageDead(_5);
_14 = discriminant((_4.0: Option2<u32>));
- switchInt(move _14) -> [0: bb2, 1: bb4, 2: bb6, otherwise: bb12];
+ StorageLive(_18);
+ _18 = discriminant((_4.1: Option2<u32>));
+ StorageLive(_19);
+ _19 = Ne(copy _14, move _18);
+ StorageDead(_18);
+ switchInt(move _19) -> [0: bb10, otherwise: bb1];
}
bb1: {
+ StorageDead(_19);
_0 = const 1_u32;
- goto -> bb11;
+ goto -> bb8;
@ -134,7 +130,6 @@
+ }
+
+ bb10: {
+ StorageDead(_19);
+ switchInt(copy _14) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
}
}