Use Copy in the SwitchInt terminator

dianqk · dianqk · commit 8c1875b9d703 · 2026-01-10T21:44:47.000+08:00
Move can be used only when both the compared operand and the operand on switch are move operands.
This commit directly changes to Copy, because I don't know if Move has beneficial.
diff --git a/compiler/rustc_mir_transform/src/simplify_comparison_integral.rs b/compiler/rustc_mir_transform/src/simplify_comparison_integral.rs
@@ -136,7 +136,7 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyComparisonIntegral {
 
             let terminator = bb.terminator_mut();
             terminator.kind =
-                TerminatorKind::SwitchInt { discr: Operand::Move(opt.to_switch_on), targets };
+                TerminatorKind::SwitchInt { discr: Operand::Copy(opt.to_switch_on), targets };
         }
 
         for (idx, bb_idx) in storage_deads_to_remove {
diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.32bit.panic-abort.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.32bit.panic-abort.diff
@@ -74,7 +74,7 @@
           _23 = copy (((*_1).0: std::fmt::FormattingOptions).0: u32);
           _22 = BitAnd(move _23, const core::fmt::flags::PRECISION_FLAG);
           StorageDead(_23);
-          switchInt(move _22) -> [0: bb10, otherwise: bb11];
+          switchInt(copy _22) -> [0: bb10, otherwise: bb11];
       }
   
       bb4: {
diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.32bit.panic-unwind.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.32bit.panic-unwind.diff
@@ -74,7 +74,7 @@
           _23 = copy (((*_1).0: std::fmt::FormattingOptions).0: u32);
           _22 = BitAnd(move _23, const core::fmt::flags::PRECISION_FLAG);
           StorageDead(_23);
-          switchInt(move _22) -> [0: bb10, otherwise: bb11];
+          switchInt(copy _22) -> [0: bb10, otherwise: bb11];
       }
   
       bb4: {
diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.64bit.panic-abort.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.64bit.panic-abort.diff
@@ -74,7 +74,7 @@
           _23 = copy (((*_1).0: std::fmt::FormattingOptions).0: u32);
           _22 = BitAnd(move _23, const core::fmt::flags::PRECISION_FLAG);
           StorageDead(_23);
-          switchInt(move _22) -> [0: bb10, otherwise: bb11];
+          switchInt(copy _22) -> [0: bb10, otherwise: bb11];
       }
   
       bb4: {
diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.64bit.panic-unwind.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.GVN.64bit.panic-unwind.diff
@@ -74,7 +74,7 @@
           _23 = copy (((*_1).0: std::fmt::FormattingOptions).0: u32);
           _22 = BitAnd(move _23, const core::fmt::flags::PRECISION_FLAG);
           StorageDead(_23);
-          switchInt(move _22) -> [0: bb10, otherwise: bb11];
+          switchInt(copy _22) -> [0: bb10, otherwise: bb11];
       }
   
       bb4: {
diff --git a/tests/mir-opt/if_condition_int.dont_remove_comparison.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.dont_remove_comparison.SimplifyComparisonIntegral.diff
@@ -21,7 +21,7 @@
           _2 = Eq(copy _1, const 17_i8);
           StorageDead(_3);
 -         switchInt(copy _2) -> [0: bb2, otherwise: bb1];
-+         switchInt(move _1) -> [17: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [17: bb1, otherwise: bb2];
       }
   
       bb1: {
diff --git a/tests/mir-opt/if_condition_int.opt_char.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.opt_char.SimplifyComparisonIntegral.diff
@@ -14,7 +14,7 @@
 -         _2 = Eq(copy _1, const 'x');
 -         switchInt(move _2) -> [0: bb2, otherwise: bb1];
 +         nop;
-+         switchInt(move _1) -> [120: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [120: bb1, otherwise: bb2];
       }
   
       bb1: {
diff --git a/tests/mir-opt/if_condition_int.opt_i8.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.opt_i8.SimplifyComparisonIntegral.diff
@@ -14,7 +14,7 @@
 -         _2 = Eq(copy _1, const 42_i8);
 -         switchInt(move _2) -> [0: bb2, otherwise: bb1];
 +         nop;
-+         switchInt(move _1) -> [42: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [42: bb1, otherwise: bb2];
       }
   
       bb1: {
diff --git a/tests/mir-opt/if_condition_int.opt_multiple_ifs.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.opt_multiple_ifs.SimplifyComparisonIntegral.diff
@@ -16,7 +16,7 @@
 -         _2 = Eq(copy _1, const 42_u32);
 -         switchInt(move _2) -> [0: bb2, otherwise: bb1];
 +         nop;
-+         switchInt(move _1) -> [42: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [42: bb1, otherwise: bb2];
       }
   
       bb1: {
@@ -33,7 +33,7 @@
 -         _4 = Ne(copy _1, const 21_u32);
 -         switchInt(move _4) -> [0: bb4, otherwise: bb3];
 +         nop;
-+         switchInt(move _1) -> [21: bb4, otherwise: bb3];
++         switchInt(copy _1) -> [21: bb4, otherwise: bb3];
       }
   
       bb3: {
diff --git a/tests/mir-opt/if_condition_int.opt_negative.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.opt_negative.SimplifyComparisonIntegral.diff
@@ -14,7 +14,7 @@
 -         _2 = Eq(copy _1, const -42_i32);
 -         switchInt(move _2) -> [0: bb2, otherwise: bb1];
 +         nop;
-+         switchInt(move _1) -> [4294967254: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [4294967254: bb1, otherwise: bb2];
       }
   
       bb1: {
diff --git a/tests/mir-opt/if_condition_int.opt_u32.SimplifyComparisonIntegral.diff b/tests/mir-opt/if_condition_int.opt_u32.SimplifyComparisonIntegral.diff
@@ -14,7 +14,7 @@
 -         _2 = Eq(copy _1, const 42_u32);
 -         switchInt(move _2) -> [0: bb2, otherwise: bb1];
 +         nop;
-+         switchInt(move _1) -> [42: bb1, otherwise: bb2];
++         switchInt(copy _1) -> [42: bb1, otherwise: bb2];
       }
   
       bb1: {
diff --git a/tests/mir-opt/if_condition_int.rs b/tests/mir-opt/if_condition_int.rs
@@ -10,8 +10,7 @@ use core::intrinsics::mir::*;
 // EMIT_MIR if_condition_int.opt_u32.SimplifyComparisonIntegral.diff
 fn opt_u32(x: u32) -> u32 {
     // CHECK-LABEL: fn opt_u32(
-    // FIXME: This should be copy.
-    // CHECK: switchInt(move _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: _0 = const 0_u32;
     // CHECK: [[BB2]]:
@@ -34,7 +33,7 @@ fn dont_opt_bool(x: bool) -> u32 {
 // EMIT_MIR if_condition_int.opt_char.SimplifyComparisonIntegral.diff
 fn opt_char(x: char) -> u32 {
     // CHECK-LABEL: fn opt_char(
-    // CHECK: switchInt(move _1) -> [120: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [120: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: _0 = const 0_u32;
     // CHECK: [[BB2]]:
@@ -45,7 +44,7 @@ fn opt_char(x: char) -> u32 {
 // EMIT_MIR if_condition_int.opt_i8.SimplifyComparisonIntegral.diff
 fn opt_i8(x: i8) -> u32 {
     // CHECK-LABEL: fn opt_i8(
-    // CHECK: switchInt(move _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: _0 = const 0_u32;
     // CHECK: [[BB2]]:
@@ -56,7 +55,7 @@ fn opt_i8(x: i8) -> u32 {
 // EMIT_MIR if_condition_int.opt_negative.SimplifyComparisonIntegral.diff
 fn opt_negative(x: i32) -> u32 {
     // CHECK-LABEL: fn opt_negative(
-    // CHECK: switchInt(move _1) -> [4294967254: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [4294967254: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: _0 = const 0_u32;
     // CHECK: [[BB2]]:
@@ -67,11 +66,11 @@ fn opt_negative(x: i32) -> u32 {
 // EMIT_MIR if_condition_int.opt_multiple_ifs.SimplifyComparisonIntegral.diff
 fn opt_multiple_ifs(x: u32) -> u32 {
     // CHECK-LABEL: fn opt_multiple_ifs(
-    // CHECK: switchInt(move _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [42: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: _0 = const 0_u32;
     // CHECK: [[BB2]]:
-    // CHECK: switchInt(move _1) -> [21: [[BB4:bb.*]], otherwise: [[BB3:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [21: [[BB4:bb.*]], otherwise: [[BB3:bb.*]]];
     // CHECK: [[BB3]]:
     // CHECK: _0 = const 1_u32;
     // CHECK: [[BB4]]:
@@ -90,7 +89,7 @@ fn opt_multiple_ifs(x: u32) -> u32 {
 fn dont_remove_comparison(a: i8) -> i32 {
     // CHECK-LABEL: fn dont_remove_comparison(
     // CHECK: [[b:_.*]] = Eq(copy _1, const 17_i8);
-    // CHECK: switchInt(move _1) -> [17: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
+    // CHECK: switchInt(copy _1) -> [17: [[BB1:bb.*]], otherwise: [[BB2:bb.*]]];
     // CHECK: [[BB1]]:
     // CHECK: [[cast_1:_.*]] = copy [[b]] as i32 (IntToInt);
     // CHECK: _0 = Add(const 100_i32, move [[cast_1]]);
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.32bit.panic-abort.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.32bit.panic-abort.mir
@@ -28,7 +28,7 @@ fn num_to_digit(_1: char) -> u32 {
         StorageLive(_3);
         _3 = discriminant(_2);
         StorageDead(_2);
-        switchInt(move _3) -> [1: bb2, otherwise: bb7];
+        switchInt(copy _3) -> [1: bb2, otherwise: bb7];
     }
 
     bb2: {
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.32bit.panic-unwind.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.32bit.panic-unwind.mir
@@ -28,7 +28,7 @@ fn num_to_digit(_1: char) -> u32 {
         StorageLive(_3);
         _3 = discriminant(_2);
         StorageDead(_2);
-        switchInt(move _3) -> [1: bb2, otherwise: bb7];
+        switchInt(copy _3) -> [1: bb2, otherwise: bb7];
     }
 
     bb2: {
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.64bit.panic-abort.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.64bit.panic-abort.mir
@@ -28,7 +28,7 @@ fn num_to_digit(_1: char) -> u32 {
         StorageLive(_3);
         _3 = discriminant(_2);
         StorageDead(_2);
-        switchInt(move _3) -> [1: bb2, otherwise: bb7];
+        switchInt(copy _3) -> [1: bb2, otherwise: bb7];
     }
 
     bb2: {
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.64bit.panic-unwind.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.64bit.panic-unwind.mir
@@ -28,7 +28,7 @@ fn num_to_digit(_1: char) -> u32 {
         StorageLive(_3);
         _3 = discriminant(_2);
         StorageDead(_2);
-        switchInt(move _3) -> [1: bb2, otherwise: bb7];
+        switchInt(copy _3) -> [1: bb2, otherwise: bb7];
     }
 
     bb2: {

Original file line number	Diff line number	Diff line change
`@@ -136,7 +136,7 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyComparisonIntegral {`
`136`	`136`
`137`	`137`	`let terminator = bb.terminator_mut();`
`138`	`138`	`terminator.kind =`
`139`		`- TerminatorKind::SwitchInt { discr: Operand::Move(opt.to_switch_on), targets };`
	`139`	`+ TerminatorKind::SwitchInt { discr: Operand::Copy(opt.to_switch_on), targets };`
`140`	`140`	`}`
`141`	`141`
`142`	`142`	`for (idx, bb_idx) in storage_deads_to_remove {`
Original file line number	Diff line number	Diff line change
`@@ -74,7 +74,7 @@`
`74`	`74`	`_23 = copy (((*_1).0: std::fmt::FormattingOptions).0: u32);`
`75`	`75`	`_22 = BitAnd(move _23, const core::fmt::flags::PRECISION_FLAG);`
`76`	`76`	`StorageDead(_23);`
`77`		`- switchInt(move _22) -> [0: bb10, otherwise: bb11];`
	`77`	`+ switchInt(copy _22) -> [0: bb10, otherwise: bb11];`
`78`	`78`	`}`
`79`	`79`
`80`	`80`	`bb4: {`
Original file line number	Diff line number	Diff line change
`@@ -21,7 +21,7 @@`
`21`	`21`	`_2 = Eq(copy _1, const 17_i8);`
`22`	`22`	`StorageDead(_3);`
`23`	`23`	`- switchInt(copy _2) -> [0: bb2, otherwise: bb1];`
`24`		`-+ switchInt(move _1) -> [17: bb1, otherwise: bb2];`
	`24`	`++ switchInt(copy _1) -> [17: bb1, otherwise: bb2];`
`25`	`25`	`}`
`26`	`26`
`27`	`27`	`bb1: {`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@`
`14`	`14`	`- _2 = Eq(copy _1, const 'x');`
`15`	`15`	`- switchInt(move _2) -> [0: bb2, otherwise: bb1];`
`16`	`16`	`+ nop;`
`17`		`-+ switchInt(move _1) -> [120: bb1, otherwise: bb2];`
	`17`	`++ switchInt(copy _1) -> [120: bb1, otherwise: bb2];`
`18`	`18`	`}`
`19`	`19`
`20`	`20`	`bb1: {`