Auto merge of #38265 - bluss:mir-deaggregator-loop, r=nagisa
Reinstate while loop in deaggregator pass A previous commit must have removed the `while let` loop here by mistake; for each basic block, it should find and deaggregate multiple statements in their index order, and the `curr` index tracks the progress through the block. This fixes both the case of deaggregating statements in separate basic blocks (preserving `curr` could prevent that) as well as multiple times in the same block (missing loop prevented that). The loop was lost in commit bda46c21fe30377b9587b584c64ffe99da6c14ce.
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commit
3db197aa9d
@ -36,71 +36,70 @@ impl<'tcx> MirPass<'tcx> for Deaggregator {
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// In fact, we might not want to trigger in other cases.
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// Ex: when we could use SROA. See issue #35259
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let mut curr: usize = 0;
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for bb in mir.basic_blocks_mut() {
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let idx = match get_aggregate_statement_index(curr, &bb.statements) {
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Some(idx) => idx,
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None => continue,
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};
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// do the replacement
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debug!("removing statement {:?}", idx);
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let src_info = bb.statements[idx].source_info;
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let suffix_stmts = bb.statements.split_off(idx+1);
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let orig_stmt = bb.statements.pop().unwrap();
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let (lhs, rhs) = match orig_stmt.kind {
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StatementKind::Assign(ref lhs, ref rhs) => (lhs, rhs),
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_ => span_bug!(src_info.span, "expected assign, not {:?}", orig_stmt),
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};
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let (agg_kind, operands) = match rhs {
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&Rvalue::Aggregate(ref agg_kind, ref operands) => (agg_kind, operands),
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_ => span_bug!(src_info.span, "expected aggregate, not {:?}", rhs),
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};
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let (adt_def, variant, substs) = match agg_kind {
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&AggregateKind::Adt(adt_def, variant, substs, None) => (adt_def, variant, substs),
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_ => span_bug!(src_info.span, "expected struct, not {:?}", rhs),
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};
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let n = bb.statements.len();
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bb.statements.reserve(n + operands.len() + suffix_stmts.len());
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for (i, op) in operands.iter().enumerate() {
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let ref variant_def = adt_def.variants[variant];
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let ty = variant_def.fields[i].ty(tcx, substs);
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let rhs = Rvalue::Use(op.clone());
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let mut curr: usize = 0;
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while let Some(idx) = get_aggregate_statement_index(curr, &bb.statements) {
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// do the replacement
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debug!("removing statement {:?}", idx);
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let src_info = bb.statements[idx].source_info;
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let suffix_stmts = bb.statements.split_off(idx+1);
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let orig_stmt = bb.statements.pop().unwrap();
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let (lhs, rhs) = match orig_stmt.kind {
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StatementKind::Assign(ref lhs, ref rhs) => (lhs, rhs),
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_ => span_bug!(src_info.span, "expected assign, not {:?}", orig_stmt),
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};
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let (agg_kind, operands) = match rhs {
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&Rvalue::Aggregate(ref agg_kind, ref operands) => (agg_kind, operands),
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_ => span_bug!(src_info.span, "expected aggregate, not {:?}", rhs),
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};
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let (adt_def, variant, substs) = match agg_kind {
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&AggregateKind::Adt(adt_def, variant, substs, None)
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=> (adt_def, variant, substs),
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_ => span_bug!(src_info.span, "expected struct, not {:?}", rhs),
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};
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let n = bb.statements.len();
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bb.statements.reserve(n + operands.len() + suffix_stmts.len());
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for (i, op) in operands.iter().enumerate() {
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let ref variant_def = adt_def.variants[variant];
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let ty = variant_def.fields[i].ty(tcx, substs);
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let rhs = Rvalue::Use(op.clone());
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let lhs_cast = if adt_def.variants.len() > 1 {
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Lvalue::Projection(Box::new(LvalueProjection {
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base: lhs.clone(),
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elem: ProjectionElem::Downcast(adt_def, variant),
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}))
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} else {
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lhs.clone()
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let lhs_cast = if adt_def.variants.len() > 1 {
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Lvalue::Projection(Box::new(LvalueProjection {
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base: lhs.clone(),
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elem: ProjectionElem::Downcast(adt_def, variant),
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}))
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} else {
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lhs.clone()
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};
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let lhs_proj = Lvalue::Projection(Box::new(LvalueProjection {
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base: lhs_cast,
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elem: ProjectionElem::Field(Field::new(i), ty),
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}));
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let new_statement = Statement {
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source_info: src_info,
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kind: StatementKind::Assign(lhs_proj, rhs),
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};
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debug!("inserting: {:?} @ {:?}", new_statement, idx + i);
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bb.statements.push(new_statement);
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}
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// if the aggregate was an enum, we need to set the discriminant
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if adt_def.variants.len() > 1 {
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let set_discriminant = Statement {
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kind: StatementKind::SetDiscriminant {
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lvalue: lhs.clone(),
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variant_index: variant,
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},
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source_info: src_info,
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};
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bb.statements.push(set_discriminant);
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};
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let lhs_proj = Lvalue::Projection(Box::new(LvalueProjection {
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base: lhs_cast,
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elem: ProjectionElem::Field(Field::new(i), ty),
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}));
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let new_statement = Statement {
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source_info: src_info,
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kind: StatementKind::Assign(lhs_proj, rhs),
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};
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debug!("inserting: {:?} @ {:?}", new_statement, idx + i);
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bb.statements.push(new_statement);
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curr = bb.statements.len();
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bb.statements.extend(suffix_stmts);
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}
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// if the aggregate was an enum, we need to set the discriminant
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if adt_def.variants.len() > 1 {
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let set_discriminant = Statement {
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kind: StatementKind::SetDiscriminant {
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lvalue: lhs.clone(),
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variant_index: variant,
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},
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source_info: src_info,
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};
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bb.statements.push(set_discriminant);
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};
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curr = bb.statements.len();
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bb.statements.extend(suffix_stmts);
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}
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}
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}
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57
src/test/mir-opt/deaggregator_test_enum_2.rs
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57
src/test/mir-opt/deaggregator_test_enum_2.rs
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@ -0,0 +1,57 @@
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test that deaggregate fires in more than one basic block
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enum Foo {
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A(i32),
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B(i32),
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}
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fn test1(x: bool, y: i32) -> Foo {
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if x {
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Foo::A(y)
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} else {
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Foo::B(y)
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}
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}
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fn main() {}
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// END RUST SOURCE
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// START rustc.node12.Deaggregator.before.mir
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// bb1: {
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// _6 = _4;
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// _0 = Foo::A(_6,);
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// goto -> bb3;
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// }
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//
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// bb2: {
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// _7 = _4;
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// _0 = Foo::B(_7,);
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// goto -> bb3;
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// }
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// END rustc.node12.Deaggregator.before.mir
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// START rustc.node12.Deaggregator.after.mir
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// bb1: {
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// _6 = _4;
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// ((_0 as A).0: i32) = _6;
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// discriminant(_0) = 0;
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// goto -> bb3;
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// }
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//
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// bb2: {
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// _7 = _4;
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// ((_0 as B).0: i32) = _7;
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// discriminant(_0) = 1;
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// goto -> bb3;
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// }
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// END rustc.node12.Deaggregator.after.mir
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//
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48
src/test/mir-opt/deaggregator_test_multiple.rs
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48
src/test/mir-opt/deaggregator_test_multiple.rs
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@ -0,0 +1,48 @@
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test that deaggregate fires more than once per block
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enum Foo {
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A(i32),
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B,
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}
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fn test(x: i32) -> [Foo; 2] {
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[Foo::A(x), Foo::A(x)]
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}
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fn main() { }
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// END RUST SOURCE
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// START rustc.node10.Deaggregator.before.mir
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// bb0: {
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// _2 = _1;
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// _4 = _2;
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// _3 = Foo::A(_4,);
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// _6 = _2;
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// _5 = Foo::A(_6,);
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// _0 = [_3, _5];
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// return;
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// }
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// END rustc.node10.Deaggregator.before.mir
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// START rustc.node10.Deaggregator.after.mir
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// bb0: {
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// _2 = _1;
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// _4 = _2;
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// ((_3 as A).0: i32) = _4;
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// discriminant(_3) = 0;
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// _6 = _2;
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// ((_5 as A).0: i32) = _6;
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// discriminant(_5) = 0;
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// _0 = [_3, _5];
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// return;
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// }
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// END rustc.node10.Deaggregator.after.mir
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