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rust/tests/mir-opt/jump_threading.rs
Tomasz Miąsko 1be1c2ebcf Fix insertion of statements to be executed along return edge in inlining 
Inlining creates additional statements to be executed along the return
edge: an assignment to the destination, storage end for temporaries.

Previously those statements where inserted directly into a call target,
but this is incorrect when the target has other predecessors.

Avoid the issue by creating a new dedicated block for those statements.
When the block happens to be redundant it will be removed by CFG
simplification that follows inlining.

Fixes #117355
2023-11-20 09:27:30 +01:00

481 lines
13 KiB
Rust
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// unit-test: JumpThreading
// compile-flags: -Zmir-enable-passes=+Inline
// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
#![feature(control_flow_enum)]
#![feature(try_trait_v2)]
#![feature(custom_mir, core_intrinsics, rustc_attrs)]
use std::intrinsics::mir::*;
use std::ops::ControlFlow;
fn too_complex(x: Result<i32, usize>) -> Option<i32> {
// CHECK-LABEL: fn too_complex(
// CHECK: bb0: {
// CHECK: switchInt(move {{_.*}}) -> [0: bb3, 1: bb1, otherwise: bb2];
// CHECK: bb1: {
// CHECK: [[controlflow:_.*]] = ControlFlow::<usize, i32>::Break(
// CHECK: goto -> bb8;
// CHECK: bb2: {
// CHECK: unreachable;
// CHECK: bb3: {
// CHECK: [[controlflow]] = ControlFlow::<usize, i32>::Continue(
// CHECK: goto -> bb4;
// CHECK: bb4: {
// CHECK: goto -> bb6;
// CHECK: bb5: {
// CHECK: {{_.*}} = (([[controlflow]] as Break).0: usize);
// CHECK: _0 = Option::<i32>::None;
// CHECK: goto -> bb7;
// CHECK: bb6: {
// CHECK: {{_.*}} = (([[controlflow]] as Continue).0: i32);
// CHECK: _0 = Option::<i32>::Some(
// CHECK: goto -> bb7;
// CHECK: bb7: {
// CHECK: return;
// CHECK: bb8: {
// CHECK: goto -> bb5;
match {
match x {
Ok(v) => ControlFlow::Continue(v),
Err(r) => ControlFlow::Break(r),
}
} {
ControlFlow::Continue(v) => Some(v),
ControlFlow::Break(r) => None,
}
}
fn identity(x: Result<i32, i32>) -> Result<i32, i32> {
// CHECK-LABEL: fn identity(
// CHECK: bb0: {
// CHECK: [[x:_.*]] = _1;
// CHECK: switchInt(move {{_.*}}) -> [0: bb8, 1: bb6, otherwise: bb7];
// CHECK: bb1: {
// CHECK: {{_.*}} = (([[controlflow:_.*]] as Continue).0: i32);
// CHECK: _0 = Result::<i32, i32>::Ok(
// CHECK: goto -> bb4;
// CHECK: bb2: {
// CHECK: unreachable;
// CHECK: bb3: {
// CHECK: {{_.*}} = (([[controlflow]] as Break).0: std::result::Result<std::convert::Infallible, i32>);
// CHECK: _0 = Result::<i32, i32>::Err(
// CHECK: goto -> bb4;
// CHECK: bb4: {
// CHECK: return;
// CHECK: bb5: {
// CHECK: goto -> bb1;
// CHECK: bb6: {
// CHECK: {{_.*}} = move (([[x]] as Err).0: i32);
// CHECK: [[controlflow]] = ControlFlow::<Result<Infallible, i32>, i32>::Break(
// CHECK: goto -> bb9;
// CHECK: bb7: {
// CHECK: unreachable;
// CHECK: bb8: {
// CHECK: {{_.*}} = move (([[x]] as Ok).0: i32);
// CHECK: [[controlflow]] = ControlFlow::<Result<Infallible, i32>, i32>::Continue(
// CHECK: goto -> bb5;
// CHECK: bb9: {
// CHECK: goto -> bb3;
Ok(x?)
}
enum DFA {
A,
B,
C,
D,
}
/// Check that we do not thread through a loop header,
/// to avoid creating an irreducible CFG.
fn dfa() {
// CHECK-LABEL: fn dfa(
// CHECK: bb0: {
// CHECK: {{_.*}} = DFA::A;
// CHECK: goto -> bb1;
// CHECK: bb1: {
// CHECK: switchInt({{.*}}) -> [0: bb4, 1: bb5, 2: bb6, 3: bb2, otherwise: bb3];
// CHECK: bb2: {
// CHECK: return;
// CHECK: bb3: {
// CHECK: unreachable;
// CHECK: bb4: {
// CHECK: {{_.*}} = DFA::B;
// CHECK: goto -> bb1;
// CHECK: bb5: {
// CHECK: {{_.*}} = DFA::C;
// CHECK: goto -> bb1;
// CHECK: bb6: {
// CHECK: {{_.*}} = DFA::D;
// CHECK: goto -> bb1;
let mut state = DFA::A;
loop {
match state {
DFA::A => state = DFA::B,
DFA::B => state = DFA::C,
DFA::C => state = DFA::D,
DFA::D => return,
}
}
}
#[repr(u8)]
enum CustomDiscr {
A = 35,
B = 73,
C = 99,
}
/// Verify that we correctly match the discriminant value, and not its index.
fn custom_discr(x: bool) -> u8 {
// CHECK-LABEL: fn custom_discr(
// CHECK: bb0: {
// CHECK: switchInt({{.*}}) -> [0: bb2, otherwise: bb1];
// CHECK: bb1: {
// CHECK: {{_.*}} = CustomDiscr::A;
// CHECK: goto -> bb7;
// CHECK: bb2: {
// CHECK: {{_.*}} = CustomDiscr::B;
// CHECK: goto -> bb3;
// CHECK: bb3: {
// CHECK: goto -> bb4;
// CHECK: bb4: {
// CHECK: _0 = const 13_u8;
// CHECK: goto -> bb6;
// CHECK: bb5: {
// CHECK: _0 = const 5_u8;
// CHECK: goto -> bb6;
// CHECK: bb6: {
// CHECK: return;
// CHECK: bb7: {
// CHECK: goto -> bb5;
match if x { CustomDiscr::A } else { CustomDiscr::B } {
CustomDiscr::A => 5,
_ => 13,
}
}
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn multiple_match(x: u8) -> u8 {
// CHECK-LABEL: fn multiple_match(
mir!(
{
// CHECK: bb0: {
// CHECK: switchInt([[x:_.*]]) -> [3: bb1, otherwise: bb2];
match x { 3 => bb1, _ => bb2 }
}
bb1 = {
// We know `x == 3`, so we can take `bb3`.
// CHECK: bb1: {
// CHECK: {{_.*}} = [[x]];
// CHECK: goto -> bb3;
let y = x;
match y { 3 => bb3, _ => bb4 }
}
bb2 = {
// We know `x != 3`, so we can take `bb6`.
// CHECK: bb2: {
// CHECK: [[z:_.*]] = [[x]];
// CHECK: goto -> bb6;
let z = x;
match z { 3 => bb5, _ => bb6 }
}
bb3 = {
// CHECK: bb3: {
// CHECK: _0 = const 5_u8;
// CHECK: return;
RET = 5;
Return()
}
bb4 = {
// CHECK: bb4: {
// CHECK: _0 = const 7_u8;
// CHECK: return;
RET = 7;
Return()
}
bb5 = {
// CHECK: bb5: {
// CHECK: _0 = const 9_u8;
// CHECK: return;
RET = 9;
Return()
}
bb6 = {
// We know `z != 3`, so we CANNOT take `bb7`.
// CHECK: bb6: {
// CHECK: switchInt([[z]]) -> [1: bb7, otherwise: bb8];
match z { 1 => bb7, _ => bb8 }
}
bb7 = {
// CHECK: bb7: {
// CHECK: _0 = const 9_u8;
// CHECK: return;
RET = 9;
Return()
}
bb8 = {
// CHECK: bb8: {
// CHECK: _0 = const 11_u8;
// CHECK: return;
RET = 11;
Return()
}
)
}
/// Both 1-3-4 and 2-3-4 are threadable. As 1 and 2 are the only predecessors of 3,
/// verify that we only thread the 3-4 part.
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn duplicate_chain(x: bool) -> u8 {
// CHECK-LABEL: fn duplicate_chain(
mir!(
let a: u8;
{
// CHECK: bb0: {
// CHECK: switchInt({{.*}}) -> [1: bb1, otherwise: bb2];
match x { true => bb1, _ => bb2 }
}
bb1 = {
// CHECK: bb1: {
// CHECK: [[a:_.*]] = const 5_u8;
// CHECK: goto -> bb3;
a = 5;
Goto(bb3)
}
bb2 = {
// CHECK: bb2: {
// CHECK: [[a]] = const 5_u8;
// CHECK: goto -> bb3;
a = 5;
Goto(bb3)
}
bb3 = {
// CHECK: bb3: {
// CHECK: {{_.*}} = const 13_i32;
// CHECK: goto -> bb4;
let b = 13;
Goto(bb4)
}
bb4 = {
// CHECK: bb4: {
// CHECK: {{_.*}} = const 15_i32;
// CHECK-NOT: switchInt(
// CHECK: goto -> bb5;
let c = 15;
match a { 5 => bb5, _ => bb6 }
}
bb5 = {
// CHECK: bb5: {
// CHECK: _0 = const 7_u8;
// CHECK: return;
RET = 7;
Return()
}
bb6 = {
// CHECK: bb6: {
// CHECK: _0 = const 9_u8;
// CHECK: return;
RET = 9;
Return()
}
)
}
#[rustc_layout_scalar_valid_range_start(1)]
#[rustc_nonnull_optimization_guaranteed]
struct NonZeroUsize(usize);
/// Verify that we correctly discard threads that may mutate a discriminant by aliasing.
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn mutate_discriminant() -> u8 {
// CHECK-LABEL: fn mutate_discriminant(
// CHECK-NOT: goto -> {{bb.*}};
// CHECK: switchInt(
// CHECK-NOT: goto -> {{bb.*}};
mir!(
let x: Option<NonZeroUsize>;
{
SetDiscriminant(x, 1);
// This assignment overwrites the niche in which the discriminant is stored.
place!(Field(Field(Variant(x, 1), 0), 0)) = 0_usize;
// So we cannot know the value of this discriminant.
let a = Discriminant(x);
match a {
0 => bb1,
_ => bad,
}
}
bb1 = {
RET = 1;
Return()
}
bad = {
RET = 2;
Unreachable()
}
)
}
/// Verify that we do not try to reason when there are mutable pointers involved.
fn mutable_ref() -> bool {
// CHECK-LABEL: fn mutable_ref(
// CHECK-NOT: goto -> {{bb.*}};
// CHECK: switchInt(
// CHECK: goto -> [[bbret:bb.*]];
// CHECK: goto -> [[bbret]];
// CHECK: [[bbret]]: {
// CHECK-NOT: {{bb.*}}: {
// CHECK: return;
let mut x = 5;
let a = std::ptr::addr_of_mut!(x);
x = 7;
unsafe { *a = 8 };
if x == 7 {
true
} else {
false
}
}
/// This function has 2 TOs: 1-3-4 and 0-1-3-4-6.
/// We verify that the second TO does not modify 3 once the first has been applied.
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn renumbered_bb(x: bool) -> u8 {
// CHECK-LABEL: fn renumbered_bb(
mir!(
let a: bool;
let b: bool;
{
// CHECK: bb0: {
// CHECK: switchInt({{.*}}) -> [1: bb1, otherwise: bb2];
b = false;
match x { true => bb1, _ => bb2 }
}
bb1 = {
// CHECK: bb1: {
// CHECK: goto -> bb8;
a = false;
Goto(bb3)
}
bb2 = {
// CHECK: bb2: {
// CHECK: goto -> bb3;
a = x;
b = x;
Goto(bb3)
}
bb3 = {
// CHECK: bb3: {
// CHECK: switchInt({{.*}}) -> [0: bb4, otherwise: bb5];
match a { false => bb4, _ => bb5 }
}
bb4 = {
// CHECK: bb4: {
// CHECK: switchInt({{.*}}) -> [0: bb6, otherwise: bb7];
match b { false => bb6, _ => bb7 }
}
bb5 = {
// CHECK: bb5: {
// CHECK: _0 = const 7_u8;
RET = 7;
Return()
}
bb6 = {
// CHECK: bb6: {
// CHECK: _0 = const 9_u8;
RET = 9;
Return()
}
bb7 = {
// CHECK: bb7: {
// CHECK: _0 = const 11_u8;
RET = 11;
Return()
}
// Duplicate of bb3.
// CHECK: bb8: {
// CHECK-NEXT: goto -> bb9;
// Duplicate of bb4.
// CHECK: bb9: {
// CHECK-NEXT: goto -> bb6;
)
}
/// This function has 3 TOs: 1-4-5, 0-1-4-7-5-8 and 3-4-7-5-6
/// After applying the first TO, we create bb9 to replace 4, and rename 1-4 edge by 1-9. The
/// second TO may try to thread non-existing edge 9-4.
/// This test verifies that we preserve semantics by bailing out of this second TO.
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn disappearing_bb(x: u8) -> u8 {
// CHECK-LABEL: fn disappearing_bb(
mir!(
let a: bool;
let b: bool;
{
a = true;
b = true;
match x { 0 => bb3, 1 => bb3, 2 => bb1, _ => bb2 }
}
bb1 = {
// CHECK: bb1: {
// CHECK: goto -> bb9;
b = false;
Goto(bb4)
}
bb2 = {
Unreachable()
}
bb3 = {
// CHECK: bb3: {
// CHECK: goto -> bb10;
a = false;
Goto(bb4)
}
bb4 = {
match b { false => bb5, _ => bb7 }
}
bb5 = {
match a { false => bb6, _ => bb8 }
}
bb6 = {
Return()
}
bb7 = {
Goto(bb5)
}
bb8 = {
Goto(bb6)
}
// CHECK: bb9: {
// CHECK: goto -> bb5;
// CHECK: bb10: {
// CHECK: goto -> bb6;
)
}
fn main() {
too_complex(Ok(0));
identity(Ok(0));
custom_discr(false);
dfa();
multiple_match(5);
duplicate_chain(false);
mutate_discriminant();
mutable_ref();
renumbered_bb(true);
disappearing_bb(7);
}
// EMIT_MIR jump_threading.too_complex.JumpThreading.diff
// EMIT_MIR jump_threading.identity.JumpThreading.diff
// EMIT_MIR jump_threading.custom_discr.JumpThreading.diff
// EMIT_MIR jump_threading.dfa.JumpThreading.diff
// EMIT_MIR jump_threading.multiple_match.JumpThreading.diff
// EMIT_MIR jump_threading.duplicate_chain.JumpThreading.diff
// EMIT_MIR jump_threading.mutate_discriminant.JumpThreading.diff
// EMIT_MIR jump_threading.mutable_ref.JumpThreading.diff
// EMIT_MIR jump_threading.renumbered_bb.JumpThreading.diff
// EMIT_MIR jump_threading.disappearing_bb.JumpThreading.diff
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