test: Add test for debug locations

[djolertrk]

This demonstrates that simple "assert-based debugging" does not work.
The reason is that there is no source locations attached to ub.unreachable.

It can be confirmed by using following commands:

  # Build the example
  cargo build --release --target wasm32-unknown-unknown \
    --manifest-path examples/assert-debug-test/Cargo.toml

  # Check HIR with source locations  
  ./bin/midenc examples/assert-debug-test/target/wasm32-unknown-unknown/release/assert_debug_test.wasm \
    --entrypoint=assert_debug_test::test_assert \
    -Ztrim-path-prefix=examples/assert-debug-test \
    -Zprint-hir-source-locations \
    --debug full --emit=hir=-

And to run the integration test:

cargo test --release -p miden-integration-tests debug_source_locations -- --nocapture

This addresses #806.

[djolertrk]

Similar situation is when an assert_eq is being used, since in that case an intrinsic is being used that also has a default/unknown source location attached, a solution for that case can be inlining of the call to intrinsic itself, so we can find a reasonable span for it,.

[djolertrk]

cc @greenhat @bitwalker

[greenhat]

This demonstrates that simple "assert-based debugging" does not work. The reason is that there is no source locations attached to ub.unreachable.

Interesting. I see we set the passed span for the unreachable at

compiler/frontend/wasm/src/code_translator/mod.rs

Line 151 in cccf958

builder.unreachable(span);

I wonder how it ends up being lost. Or do we pass an empty span here? Any ideas?

EDIT: Oh, I'm just slow. #812 (comment) fixes it, right?

[djolertrk]

I double checked now, without changes from #812 (comment) (so basically with this branch only), we have this situation:

        public builtin.function @test_assert(v1: i32) -> i32 {
        ^block8(v1: i32):
            v3 = arith.constant 100 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":23:1);
            v4 = hir.bitcast v1 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v5 = hir.bitcast v3 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v6 = arith.gt v4, v5 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v7 = arith.zext v6 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v8 = hir.bitcast v7 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v9 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            v10 = arith.neq v8, v9 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
            cf.cond_br v10 ^block10, ^block11 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:13);
        ^block9(v2: i32):
            builtin.ret v2 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":27:1);
        ^block10:
            cf.br ^block9(v1) #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":27:1);
        ^block11:
            v11 = arith.constant 1048576 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:5);
            v12 = arith.constant 25 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:5);
            v13 = arith.constant 1048612 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:5);
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v11, v12, v13)
            ub.unreachable  #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":24:5);
        };
        
         public builtin.function @test_multiple_asserts(v14: i32, v15: i32) -> i32 {
        ^block12(v14: i32, v15: i32):
            v17 = arith.constant 0 : i32;
            v18 = arith.eq v14, v17 : i1;
            v19 = arith.zext v18 : u32;
            v20 = hir.bitcast v19 : i32;
            v21 = arith.constant 0 : i32;
            v22 = arith.neq v20, v21 : i1;
            cf.cond_br v22 ^block16, ^block17;
        ^block13(v16: i32):

        ^block14:
            v41 = arith.constant 1048708 : i32;
            v42 = arith.constant 24 : i32;
            v43 = arith.constant 1048732 : i32;
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v41, v42, v43)
            ub.unreachable ;
        ^block15:
            v38 = arith.constant 1048668 : i32;
            v39 = arith.constant 23 : i32;
            v40 = arith.constant 1048692 : i32;
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v38, v39, v40)
            ub.unreachable ;
        ^block16:
            v35 = arith.constant 1048628 : i32;
            v36 = arith.constant 23 : i32;
            v37 = arith.constant 1048652 : i32;
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v35, v36, v37)
            ub.unreachable ;
        ^block17:
            v23 = arith.constant 0 : i32;
            v24 = arith.eq v15, v23 : i1;
            v25 = arith.zext v24 : u32;
            v26 = hir.bitcast v25 : i32;
            v27 = arith.constant 0 : i32;
            v28 = arith.neq v26, v27 : i1;
            cf.cond_br v28 ^block15, ^block18;
        ^block18:
            v29 = arith.eq v14, v15 : i1;
            v30 = arith.zext v29 : u32;
            v31 = hir.bitcast v30 : i32;
            v32 = arith.constant 0 : i32;
            v33 = arith.neq v31, v32 : i1;
            cf.cond_br v33 ^block14, ^block19;
        ^block19:
            v34 = arith.add v15, v14 : i32 #[overflow = wrapping];
            builtin.ret v34;
        };

As you can see test_assert has valid source location attachments, but test_multiple_asserts has no location at all -- all of them are UNKNOWN.
However, I was able to find the root cause of the issue -- the problem is caused by the comments in the rust example (https://github.com/walnuthq/compiler/blob/pr/assert-debugging/examples/assert-debug-test/src/lib.rs#L4)... The compute_line_starts() incorrectly parses those (in a C-like style), causing source manager to incorrectly compute source locations, and that is why we ended up with no locations at all in the test_multiple_asserts.

Here is the fix 0xMiden/miden-vm#2449. So, only with this fix (we can completely forget about #812 for now), we see:

        public builtin.function @test_multiple_asserts(v14: i32, v15: i32) -> i32 {
        ^block12(v14: i32, v15: i32):
            v17 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            v18 = arith.eq v14, v17 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            v19 = arith.zext v18 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            v20 = hir.bitcast v19 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            v21 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            v22 = arith.neq v20, v21 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
            cf.cond_br v22 ^block16, ^block17 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:13);
        ^block13(v16: i32):

        ^block14:
            v41 = arith.constant 1048708 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:5);
            v42 = arith.constant 24 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:5);
            v43 = arith.constant 1048732 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:5);
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v41, v42, v43)
            ub.unreachable  #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:5);
        ^block15:
            v38 = arith.constant 1048668 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:5);
            v39 = arith.constant 23 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:5);
            v40 = arith.constant 1048692 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:5);
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v38, v39, v40)
            ub.unreachable  #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:5);
        ^block16:
            v35 = arith.constant 1048628 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:5);
            v36 = arith.constant 23 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:5);
            v37 = arith.constant 1048652 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:5);
            hir.exec @root_ns:root@1.0.0/assert_debug_test/_ZN4core9panicking5panic17h4cab4a0cdc8b5cb0E(v35, v36, v37)
            ub.unreachable  #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":30:5);
        ^block17:
            v23 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            v24 = arith.eq v15, v23 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            v25 = arith.zext v24 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            v26 = hir.bitcast v25 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            v27 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            v28 = arith.neq v26, v27 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
            cf.cond_br v28 ^block15, ^block18 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":32:13);
        ^block18:
            v29 = arith.eq v14, v15 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
            v30 = arith.zext v29 : u32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
            v31 = hir.bitcast v30 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
            v32 = arith.constant 0 : i32 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
            v33 = arith.neq v31, v32 : i1 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
            cf.cond_br v33 ^block14, ^block19 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":34:13);
        ^block19:
            v34 = arith.add v15, v14 : i32 #[overflow = wrapping] #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":36:5);
            builtin.ret v34 #loc("/path/to/compiler/examples/assert-debug-test/src/lib.rs":37:2);
        };

But, for the test I added here, the miden-debug still prints:

Stack Trace:
 |-> root_ns:root@1.0.0::init in <unavailable>
 |-> root_ns:root@1.0.0::assert_debug_test::test_assert in <unavailable>
 |-> root_ns:root@1.0.0::assert_debug_test::core::panicking::panic in <unavailable>
 `-> root_ns:root@1.0.0::assert_debug_test::core::panicking::panic_fmt in <unavailable>:

Last 3 Instructions (of current frame):
 |   drop
 |   drop
 |   pad
 `-> <error occured here>


Last 5 Instructions (any frame):
 |   u32add
 |   drop
 |   noop
 |   drop
 |   pad
 `-> <error occured here>

[greenhat]

So we have source location for the panic function call but no source code for the unreachable op inside it. I wonder if miden-debug could go up the stack and find the first source span. But it would not help when we're running in the VM through the miden-client. So whatever solution we find needs to be implemented in the VM.
@bitwalker thoughts?

[greenhat]

@djolertrk good catch! Great job!