Rollup merge of #102778 - nbdd0121:mir, r=tmiasko

Fix MIR inlining of asm_unwind

The MIR inlining currently doesn't handle inline asm's unwind edge correctly.

This code will cause ICE:
```rust
struct D;

impl Drop for D {
    fn drop(&mut self) {}
}

#[inline(always)]
fn foo() {
    let _d = D;
    unsafe { std::arch::asm!("", options(may_unwind)) };
}

pub fn main() {
    foo();
}
```

This PR fixes this issue. I also take the opportunity to extract common code into a method.

compiler/rustc_mir_transform/src/inline.rs

@@ -977,6 +977,21 @@ impl Integrator<'_, '_> {
         trace!("mapping block `{:?}` to `{:?}`", block, new);
         new
     }
+
+    fn map_unwind(&self, unwind: Option<BasicBlock>) -> Option<BasicBlock> {
+        if self.in_cleanup_block {
+            if unwind.is_some() {
+                bug!("cleanup on cleanup block");
+            }
+            return unwind;
+        }
+
+        match unwind {
+            Some(target) => Some(self.map_block(target)),
+            // Add an unwind edge to the original call's cleanup block
+            None => self.cleanup_block,
+        }
+    }
 }
 
 impl<'tcx> MutVisitor<'tcx> for Integrator<'_, 'tcx> {
@@ -1085,35 +1100,17 @@ impl<'tcx> MutVisitor<'tcx> for Integrator<'_, 'tcx> {
             TerminatorKind::Drop { ref mut target, ref mut unwind, .. }
             | TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
                 *target = self.map_block(*target);
-                if let Some(tgt) = *unwind {
-                    *unwind = Some(self.map_block(tgt));
-                } else if !self.in_cleanup_block {
-                    // Unless this drop is in a cleanup block, add an unwind edge to
-                    // the original call's cleanup block
-                    *unwind = self.cleanup_block;
-                }
+                *unwind = self.map_unwind(*unwind);
             }
             TerminatorKind::Call { ref mut target, ref mut cleanup, .. } => {
                 if let Some(ref mut tgt) = *target {
                     *tgt = self.map_block(*tgt);
                 }
-                if let Some(tgt) = *cleanup {
-                    *cleanup = Some(self.map_block(tgt));
-                } else if !self.in_cleanup_block {
-                    // Unless this call is in a cleanup block, add an unwind edge to
-                    // the original call's cleanup block
-                    *cleanup = self.cleanup_block;
-                }
+                *cleanup = self.map_unwind(*cleanup);
             }
             TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
                 *target = self.map_block(*target);
-                if let Some(tgt) = *cleanup {
-                    *cleanup = Some(self.map_block(tgt));
-                } else if !self.in_cleanup_block {
-                    // Unless this assert is in a cleanup block, add an unwind edge to
-                    // the original call's cleanup block
-                    *cleanup = self.cleanup_block;
-                }
+                *cleanup = self.map_unwind(*cleanup);
             }
             TerminatorKind::Return => {
                 terminator.kind = if let Some(tgt) = self.callsite.target {
@@ -1141,11 +1138,8 @@ impl<'tcx> MutVisitor<'tcx> for Integrator<'_, 'tcx> {
             TerminatorKind::InlineAsm { ref mut destination, ref mut cleanup, .. } => {
                 if let Some(ref mut tgt) = *destination {
                     *tgt = self.map_block(*tgt);
-                } else if !self.in_cleanup_block {
-                    // Unless this inline asm is in a cleanup block, add an unwind edge to
-                    // the original call's cleanup block
-                    *cleanup = self.cleanup_block;
                 }
+                *cleanup = self.map_unwind(*cleanup);
             }
         }
     }

src/test/mir-opt/inline/asm-unwind.rs

@@ -0,0 +1,22 @@
+// Tests inlining of `may_unwind` inline assembly.
+//
+// ignore-wasm32-bare compiled with panic=abort by default
+// needs-asm-support
+#![feature(asm_unwind)]
+
+struct D;
+
+impl Drop for D {
+    fn drop(&mut self) {}
+}
+
+#[inline(always)]
+fn foo() {
+    let _d = D;
+    unsafe { std::arch::asm!("", options(may_unwind)) };
+}
+
+// EMIT_MIR asm_unwind.main.Inline.diff
+pub fn main() {
+    foo();
+}

src/test/mir-opt/inline/asm_unwind.main.Inline.diff

@@ -0,0 +1,45 @@
+- // MIR for `main` before Inline
++ // MIR for `main` after Inline
+
+  fn main() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/asm-unwind.rs:+0:15: +0:15
+      let _1: ();                          // in scope 0 at $DIR/asm-unwind.rs:+1:5: +1:10
++     scope 1 (inlined foo) {              // at $DIR/asm-unwind.rs:21:5: 21:10
++         let _2: D;                       // in scope 1 at $DIR/asm-unwind.rs:15:9: 15:11
++         scope 2 {
++             debug _d => _2;              // in scope 2 at $DIR/asm-unwind.rs:15:9: 15:11
++             scope 3 {
++             }
++         }
++     }
+
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/asm-unwind.rs:+1:5: +1:10
+-         _1 = foo() -> bb1;               // scope 0 at $DIR/asm-unwind.rs:+1:5: +1:10
+-                                          // mir::Constant
+-                                          // + span: $DIR/asm-unwind.rs:21:5: 21:8
+-                                          // + literal: Const { ty: fn() {foo}, val: Value(<ZST>) }
++         StorageLive(_2);                 // scope 1 at $DIR/asm-unwind.rs:15:9: 15:11
++         asm!("", options(MAY_UNWIND)) -> [return: bb1, unwind: bb3]; // scope 3 at $DIR/asm-unwind.rs:16:14: 16:54
+      }
+
+      bb1: {
++         drop(_2) -> bb2;                 // scope 1 at $DIR/asm-unwind.rs:17:1: 17:2
++     }
++ 
++     bb2: {
++         StorageDead(_2);                 // scope 1 at $DIR/asm-unwind.rs:17:1: 17:2
+          StorageDead(_1);                 // scope 0 at $DIR/asm-unwind.rs:+1:10: +1:11
+          _0 = const ();                   // scope 0 at $DIR/asm-unwind.rs:+0:15: +2:2
+          return;                          // scope 0 at $DIR/asm-unwind.rs:+2:2: +2:2
++     }
++ 
++     bb3 (cleanup): {
++         drop(_2) -> bb4;                 // scope 1 at $DIR/asm-unwind.rs:17:1: 17:2
++     }
++ 
++     bb4 (cleanup): {
++         resume;                          // scope 1 at $DIR/asm-unwind.rs:14:1: 17:2
+      }
+  }
+