[llvm] [SandboxIR] Implement UnreachableInst (PR #101856)

[via llvm-commits]

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@@ -2037,3 +2037,33 @@ define void @foo(i32 %arg) {
   }
   EXPECT_EQ(NewPHI->getNumIncomingValues(), PHI->getNumIncomingValues());
 }
+
+TEST_F(SandboxIRTest, UnreachableInst) {
+  parseIR(C, R"IR(
+define void @foo() {
+  call void @llvm.donothing()
+  unreachable
+  ret void
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vporpo wrote:

I think I figured out what the problem was. `unreachable` seemed to terminate the BB and a new BB would start right after it that includes only `ret void`. So while iterating over the instructions starting from `unreachable` we would just go out of bounds right away.

The easiest solution seems to just drop the `ret void` line.

https://github.com/llvm/llvm-project/pull/101856