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Auto merge of #106428 - saethlin:inline-diverging-functions, r=cjgillot
Permit the MIR inliner to inline diverging functions This heuristic prevents inlining of `hint::unreachable_unchecked`, which in turn makes `Option/Result::unwrap_unchecked` a bad inlining candidate. I looked through the changes to `core`, `alloc`, `std`, and `hashbrown` by hand and they all seem reasonable. Let's see how this looks in perf... --- Based on rustc-perf it looks like this regresses ctfe-stress, and the cachegrind diff indicates that this regression is in `InterpCx::statement`. I don't know how to do any deeper analysis because that function is _enormous_ in the try toolchain, which has no debuginfo in it. And a local build produces significantly different codegen for that function, even with LTO.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| #![crate_type = "lib"] | ||
| #![feature(unchecked_math)] | ||
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| // ignore-debug: the debug assertions prevent the inlining we are testing for | ||
| // compile-flags: -Zmir-opt-level=2 -Zinline-mir | ||
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| // EMIT_MIR unchecked_shifts.unchecked_shl_unsigned_smaller.Inline.diff | ||
| // EMIT_MIR unchecked_shifts.unchecked_shl_unsigned_smaller.PreCodegen.after.mir | ||
| pub unsafe fn unchecked_shl_unsigned_smaller(a: u16, b: u32) -> u16 { | ||
| a.unchecked_shl(b) | ||
| } | ||
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| // EMIT_MIR unchecked_shifts.unchecked_shr_signed_smaller.Inline.diff | ||
| // EMIT_MIR unchecked_shifts.unchecked_shr_signed_smaller.PreCodegen.after.mir | ||
| pub unsafe fn unchecked_shr_signed_smaller(a: i16, b: u32) -> i16 { | ||
| a.unchecked_shr(b) | ||
| } |
115 changes: 115 additions & 0 deletions
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tests/mir-opt/inline/unchecked_shifts.unchecked_shl_unsigned_smaller.Inline.diff
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| - // MIR for `unchecked_shl_unsigned_smaller` before Inline | ||
| + // MIR for `unchecked_shl_unsigned_smaller` after Inline | ||
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| fn unchecked_shl_unsigned_smaller(_1: u16, _2: u32) -> u16 { | ||
| debug a => _1; // in scope 0 at $DIR/unchecked_shifts.rs:+0:46: +0:47 | ||
| debug b => _2; // in scope 0 at $DIR/unchecked_shifts.rs:+0:54: +0:55 | ||
| let mut _0: u16; // return place in scope 0 at $DIR/unchecked_shifts.rs:+0:65: +0:68 | ||
| let mut _3: u16; // in scope 0 at $DIR/unchecked_shifts.rs:+1:5: +1:6 | ||
| let mut _4: u32; // in scope 0 at $DIR/unchecked_shifts.rs:+1:21: +1:22 | ||
| + scope 1 (inlined core::num::<impl u16>::unchecked_shl) { // at $DIR/unchecked_shifts.rs:10:7: 10:23 | ||
| + debug self => _3; // in scope 1 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + debug rhs => _4; // in scope 1 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + let mut _5: u16; // in scope 1 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + let mut _6: std::option::Option<u16>; // in scope 1 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + let mut _7: std::result::Result<u16, std::num::TryFromIntError>; // in scope 1 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + scope 2 { | ||
| + scope 3 (inlined Result::<u16, TryFromIntError>::ok) { // at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + debug self => _7; // in scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + let mut _8: isize; // in scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + let _9: u16; // in scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + scope 4 { | ||
| + debug x => _9; // in scope 4 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + scope 5 { | ||
| + scope 6 { | ||
| + debug x => const TryFromIntError(()); // in scope 6 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + } | ||
| + } | ||
| + scope 7 (inlined #[track_caller] Option::<u16>::unwrap_unchecked) { // at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + debug self => _6; // in scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + let mut _10: &std::option::Option<u16>; // in scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + let mut _11: isize; // in scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + scope 8 { | ||
| + debug val => _5; // in scope 8 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + } | ||
| + scope 9 { | ||
| + scope 11 (inlined unreachable_unchecked) { // at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + scope 12 { | ||
| + scope 13 (inlined unreachable_unchecked::runtime) { // at $SRC_DIR/core/src/intrinsics.rs:LL:COL | ||
| + } | ||
| + } | ||
| + } | ||
| + } | ||
| + scope 10 (inlined Option::<u16>::is_some) { // at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + debug self => _10; // in scope 10 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + } | ||
| + } | ||
| + } | ||
| + } | ||
|
|
||
| bb0: { | ||
| StorageLive(_3); // scope 0 at $DIR/unchecked_shifts.rs:+1:5: +1:6 | ||
| _3 = _1; // scope 0 at $DIR/unchecked_shifts.rs:+1:5: +1:6 | ||
| StorageLive(_4); // scope 0 at $DIR/unchecked_shifts.rs:+1:21: +1:22 | ||
| _4 = _2; // scope 0 at $DIR/unchecked_shifts.rs:+1:21: +1:22 | ||
| - _0 = core::num::<impl u16>::unchecked_shl(move _3, move _4) -> bb1; // scope 0 at $DIR/unchecked_shifts.rs:+1:5: +1:23 | ||
| + StorageLive(_5); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + StorageLive(_6); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + StorageLive(_7); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + _7 = <u32 as TryInto<u16>>::try_into(_4) -> bb1; // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| // mir::Constant | ||
| - // + span: $DIR/unchecked_shifts.rs:10:7: 10:20 | ||
| - // + literal: Const { ty: unsafe fn(u16, u32) -> u16 {core::num::<impl u16>::unchecked_shl}, val: Value(<ZST>) } | ||
| + // + span: $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + // + literal: Const { ty: fn(u32) -> Result<u16, <u32 as TryInto<u16>>::Error> {<u32 as TryInto<u16>>::try_into}, val: Value(<ZST>) } | ||
| } | ||
|
|
||
| bb1: { | ||
| + StorageLive(_9); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + _8 = discriminant(_7); // scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + switchInt(move _8) -> [0: bb6, 1: bb4, otherwise: bb5]; // scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + | ||
| + bb2: { | ||
| + StorageDead(_9); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + StorageDead(_7); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + StorageLive(_10); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + _11 = discriminant(_6); // scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + switchInt(move _11) -> [1: bb7, otherwise: bb5]; // scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + } | ||
| + | ||
| + bb3: { | ||
| + StorageDead(_5); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| StorageDead(_4); // scope 0 at $DIR/unchecked_shifts.rs:+1:22: +1:23 | ||
| StorageDead(_3); // scope 0 at $DIR/unchecked_shifts.rs:+1:22: +1:23 | ||
| return; // scope 0 at $DIR/unchecked_shifts.rs:+2:2: +2:2 | ||
| + } | ||
| + | ||
| + bb4: { | ||
| + _6 = Option::<u16>::None; // scope 6 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + goto -> bb2; // scope 5 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + | ||
| + bb5: { | ||
| + unreachable; // scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + | ||
| + bb6: { | ||
| + _9 = move ((_7 as Ok).0: u16); // scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + _6 = Option::<u16>::Some(move _9); // scope 4 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + goto -> bb2; // scope 3 at $SRC_DIR/core/src/result.rs:LL:COL | ||
| + } | ||
| + | ||
| + bb7: { | ||
| + _5 = move ((_6 as Some).0: u16); // scope 7 at $SRC_DIR/core/src/option.rs:LL:COL | ||
| + StorageDead(_10); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + StorageDead(_6); // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + _0 = unchecked_shl::<u16>(_3, move _5) -> bb3; // scope 2 at $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + // mir::Constant | ||
| + // + span: $SRC_DIR/core/src/num/uint_macros.rs:LL:COL | ||
| + // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(u16, u16) -> u16 {unchecked_shl::<u16>}, val: Value(<ZST>) } | ||
| } | ||
| } | ||
|
|
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