Auto merge of #123785 - bjorn3:sync_cg_clif-2024-04-11, r=bjorn3

Subtree sync for rustc_codegen_cranelift

This fixes an ICE for unreachable blocks.

r? `@ghost`

`@rustbot` label +A-codegen +A-cranelift +T-compiler

1 files changed, 10 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 771e5b21958..f07421431da 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -267,10 +267,19 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
         .generic_activity("codegen prelude")
         .run(|| crate::abi::codegen_fn_prelude(fx, start_block));
 
-    for (bb, bb_data) in traversal::mono_reachable(fx.mir, fx.tcx, fx.instance) {
+    let reachable_blocks = traversal::mono_reachable_as_bitset(fx.mir, fx.tcx, fx.instance);
+
+    for (bb, bb_data) in fx.mir.basic_blocks.iter_enumerated() {
         let block = fx.get_block(bb);
         fx.bcx.switch_to_block(block);
 
+        if !reachable_blocks.contains(bb) {
+            // We want to skip this block, because it's not reachable. But we still create
+            // the block so terminators in other blocks can reference it.
+            fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
+            continue;
+        }
+
         if bb_data.is_cleanup {
             // Unwinding after panicking is not supported
             continue;