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Commit 11ee3a8

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Auto merge of #131201 - compiler-errors:unop-not, r=cjgillot
Disable jump threading `UnOp::Not` for non-bool Fix #131195, where jumpthreading was optimizing `!a == b` into `a != b` for non-bool, where this is definitely not true.
2 parents 7067e4a + f0bfba2 commit 11ee3a8

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4 files changed

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4 files changed

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‎compiler/rustc_mir_transform/src/jump_threading.rs

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@@ -494,8 +494,16 @@ impl<'a, 'tcx> TOFinder<'a, 'tcx> {
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}
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// Transfer the conditions on the copy rhs, after inversing polarity.
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Rvalue::UnaryOp(UnOp::Not, Operand::Move(place) | Operand::Copy(place)) => {
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if !place.ty(self.body, self.tcx).ty.is_bool() {
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// Constructing the conditions by inverting the polarity
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// of equality is only correct for bools. That is to say,
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// `!a == b` is not `a != b` for integers greater than 1 bit.
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return;
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}
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let Some(conditions) = state.try_get_idx(lhs, &self.map) else { return };
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let Some(place) = self.map.find(place.as_ref()) else { return };
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// FIXME: I think This could be generalized to not bool if we
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// actually perform a logical not on the condition's value.
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let conds = conditions.map(self.arena, Condition::inv);
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state.insert_value_idx(place, conds, &self.map);
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}
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@@ -0,0 +1,46 @@
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- // MIR for `bitwise_not` before JumpThreading
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+ // MIR for `bitwise_not` after JumpThreading
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fn bitwise_not() -> i32 {
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let mut _0: i32;
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let mut _1: i32;
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let mut _2: bool;
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let mut _3: i32;
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let mut _4: i32;
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scope 1 {
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debug a => _1;
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}
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bb0: {
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StorageLive(_1);
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_1 = const 0_i32;
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_1 = const 1_i32;
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StorageLive(_2);
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StorageLive(_3);
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StorageLive(_4);
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_4 = copy _1;
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_3 = Not(move _4);
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StorageDead(_4);
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_2 = Eq(move _3, const 0_i32);
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switchInt(move _2) -> [0: bb2, otherwise: bb1];
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}
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bb1: {
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StorageDead(_3);
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_0 = const 1_i32;
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goto -> bb3;
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}
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bb2: {
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StorageDead(_3);
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_0 = const 0_i32;
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goto -> bb3;
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}
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bb3: {
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StorageDead(_2);
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StorageDead(_1);
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return;
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}
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}
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,46 @@
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- // MIR for `bitwise_not` before JumpThreading
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+ // MIR for `bitwise_not` after JumpThreading
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fn bitwise_not() -> i32 {
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let mut _0: i32;
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let mut _1: i32;
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let mut _2: bool;
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let mut _3: i32;
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let mut _4: i32;
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scope 1 {
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debug a => _1;
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}
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bb0: {
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StorageLive(_1);
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_1 = const 0_i32;
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_1 = const 1_i32;
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StorageLive(_2);
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StorageLive(_3);
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StorageLive(_4);
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_4 = copy _1;
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_3 = Not(move _4);
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StorageDead(_4);
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_2 = Eq(move _3, const 0_i32);
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switchInt(move _2) -> [0: bb2, otherwise: bb1];
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}
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bb1: {
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StorageDead(_3);
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_0 = const 1_i32;
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goto -> bb3;
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}
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bb2: {
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StorageDead(_3);
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_0 = const 0_i32;
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goto -> bb3;
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}
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bb3: {
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StorageDead(_2);
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StorageDead(_1);
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return;
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}
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}
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‎tests/mir-opt/jump_threading.rs

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Original file line numberDiff line numberDiff line change
@@ -531,6 +531,16 @@ fn floats() -> u32 {
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if x == 0.0 { 0 } else { 1 }
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}
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pub fn bitwise_not() -> i32 {
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// CHECK-LABEL: fn bitwise_not(
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// CHECK: switchInt(
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// Test for #131195, which was optimizing `!a == b` into `a != b`.
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let mut a: i32 = 0;
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a = 1;
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if !a == 0 { 1 } else { 0 }
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}
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fn main() {
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// CHECK-LABEL: fn main(
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too_complex(Ok(0));
@@ -562,3 +572,4 @@ fn main() {
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// EMIT_MIR jump_threading.assume.JumpThreading.diff
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// EMIT_MIR jump_threading.aggregate_copy.JumpThreading.diff
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// EMIT_MIR jump_threading.floats.JumpThreading.diff
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// EMIT_MIR jump_threading.bitwise_not.JumpThreading.diff

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