coverage: Enlarge empty spans during MIR instrumentation, not codegen

This re-lands the part of rust-lang#140847 that was (hopefully) not responsible for the coverage-instrumentation regressions that caused that PR to be reverted.

---

Enlarging empty spans was historically performed during MIR instrumentation, but had to be moved to codegen as part of larger changes in rust-lang#134497, leading to the status quo. But now there should be no reason not to move that step back to its more logical home in instrumentaion.

coverage: Enlarge empty spans during MIR instrumentation, not codegen

This re-lands the part of rust-lang#140847 that was (hopefully) not responsible for the coverage-instrumentation regressions that caused that PR to be reverted.

---

Enlarging empty spans was historically performed during MIR instrumentation, but had to be moved to codegen as part of larger changes in rust-lang#134497, leading to the status quo. But now there should be no reason not to move that step back to its more logical home in instrumentaion.

coverage: Enlarge empty spans during MIR instrumentation, not codegen

This re-lands the part of rust-lang#140847 that was (hopefully) not responsible for the coverage-instrumentation regressions that caused that PR to be reverted.

---

Enlarging empty spans was historically performed during MIR instrumentation, but had to be moved to codegen as part of larger changes in rust-lang#134497, leading to the status quo. But now there should be no reason not to move that step back to its more logical home in instrumentaion.

coverage: Enlarge empty spans during MIR instrumentation, not codegen

This re-lands the part of rust-lang#140847 that was (hopefully) not responsible for the coverage-instrumentation regressions that caused that PR to be reverted.

---

Enlarging empty spans was historically performed during MIR instrumentation, but had to be moved to codegen as part of larger changes in rust-lang#134497, leading to the status quo. But now there should be no reason not to move that step back to its more logical home in instrumentaion.

Rollup of 10 pull requests

Successful merges:

 - #144173 (Remove tidy checks for `tests/ui/issues/`)
 - #144234 (Fix broken TLS destructors on 32-bit win7)
 - #144239 (Clean `rustc/parse/src/lexer` to improve maintainability)
 - #144247 (coretests/num: use ldexp instead of hard-coding a power of 2)
 - #144256 (Don't ICE on non-TypeId metadata within TypeId)
 - #144290 (update tests/ui/SUMMARY.md)
 - #144292 (mbe: Use concrete type for `get_unused_rule`)
 - #144298 (coverage: Enlarge empty spans during MIR instrumentation, not codegen)
 - #144311 (Add powerpc64le-unknown-linux-musl to CI rustc targets)
 - #144315 (bootstrap: add package.json and package-lock.json to dist tarball)

r? `@ghost`
`@rustbot` modify labels: rollup

try-job: x86_64-gnu-aux

Rollup of 9 pull requests

Successful merges:

 - #144173 (Remove tidy checks for `tests/ui/issues/`)
 - #144234 (Fix broken TLS destructors on 32-bit win7)
 - #144239 (Clean `rustc/parse/src/lexer` to improve maintainability)
 - #144256 (Don't ICE on non-TypeId metadata within TypeId)
 - #144290 (update tests/ui/SUMMARY.md)
 - #144292 (mbe: Use concrete type for `get_unused_rule`)
 - #144298 (coverage: Enlarge empty spans during MIR instrumentation, not codegen)
 - #144311 (Add powerpc64le-unknown-linux-musl to CI rustc targets)
 - #144315 (bootstrap: add package.json and package-lock.json to dist tarball)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #144298 - Zalathar:empty-span, r=wesleywiser

coverage: Enlarge empty spans during MIR instrumentation, not codegen

This re-lands the part of #140847 that was (hopefully) not responsible for the coverage-instrumentation regressions that caused that PR to be reverted.

---

Enlarging empty spans was historically performed during MIR instrumentation, but had to be moved to codegen as part of larger changes in #134497, leading to the status quo. But now there should be no reason not to move that step back to its more logical home in instrumentaion.

Rollup merge of #144480 - Zalathar:revert-empty-span, r=Zalathar

Revert "coverage: Enlarge empty spans during MIR instrumentation, not codegen"

Surprisingly, #144298 alone (extracted from #140847) was enough to re-trigger the failures observed in #141577 (comment).

---

This reverts commit f877aa7.

---

r? ghost

coverage: Infer `instances_used` from `pgo_func_name_var_map`

In obscure circumstances involving macro-expanded spans, we would sometimes emit a covfun record for a function with no physical coverage counters, and therefore no corresponding entry in the “PGO names” section of the binary. The absence of that name entry causes `llvm-cov` to fail with the cryptic error message:

```text
malformed instrumentation profile data: function name is empty
```

We can eliminate this mismatch by removing `instances_used` entirely, and instead inferring its contents from the keys of `pgo_func_name_var_map`.

This makes it impossible for a "used" function to lack a PGO name entry.

---

This is an attempt to eliminate the cause of rust-lang#141577 when re-landing changes like rust-lang#144298 in the future.

I haven't been able to reproduce the underlying issue in an in-tree test, because the only known repro involves a non-trivial derive proc-macro that relies on `syn` and `proc-macro2`. But I have manually verified in a separate branch that this change would have prevented the reoccurrence of rust-lang#141577 (comment).

Rollup merge of #144530 - Zalathar:instances-used, r=lqd

coverage: Infer `instances_used` from `pgo_func_name_var_map`

In obscure circumstances involving macro-expanded spans, we would sometimes emit a covfun record for a function with no physical coverage counters, and therefore no corresponding entry in the “PGO names” section of the binary. The absence of that name entry causes `llvm-cov` to fail with the cryptic error message:

```text
malformed instrumentation profile data: function name is empty
```

We can eliminate this mismatch by removing `instances_used` entirely, and instead inferring its contents from the keys of `pgo_func_name_var_map`.

This makes it impossible for a "used" function to lack a PGO name entry.

---

This is an attempt to eliminate the cause of #141577 when re-landing changes like #144298 in the future.

I haven't been able to reproduce the underlying issue in an in-tree test, because the only known repro involves a non-trivial derive proc-macro that relies on `syn` and `proc-macro2`. But I have manually verified in a separate branch that this change would have prevented the reoccurrence of #141577 (comment).

Rollup merge of #144616 - Zalathar:try-in-macro, r=jieyouxu

coverage: Regression test for "function name is empty" bug

Regression test for #141577, which was triggered by #144298.

The bug was triggered by a particular usage of the `?` try operator in a proc-macro expansion.

Thanks to lqd for the minimization at #144571 (comment).

---

I have manually verified that reverting the relevant follow-up fixes (#144480 and #144530) causes this test to reproduce the bug:

```sh
git revert -m1 8aa3d41 c462895
```

---

r? compiler

coverage: Re-land "Enlarge empty spans during MIR instrumentation"

This allows us to assume that coverage spans will only be discarded during codegen in very unusual situations.

---

This seemingly-simple change has a rather messy history:
- rust-lang#140847
- rust-lang#141650
- rust-lang#144298
- rust-lang#144480

Since then, a number of related changes have landed that should make it reasonable to try again:
- rust-lang#144530
- rust-lang#144560
- rust-lang#144616

In particular, we have multiple fixes/mitigations, and a confirmed regression test for the original bug that is not triggered by re-landing the changes in this PR.

coverage: Regression test for "function name is empty" bug

Regression test for rust-lang/rust#141577, which was triggered by rust-lang/rust#144298.

The bug was triggered by a particular usage of the `?` try operator in a proc-macro expansion.

Thanks to lqd for the minimization at rust-lang/rust#144571 (comment).

---

I have manually verified that reverting the relevant follow-up fixes (rust-lang/rust#144480 and rust-lang/rust#144530) causes this test to reproduce the bug:

```sh
git revert -m1 8aa3d41b8527f9f78e0f2459b50a6e13aea35144 c462895a6f0b463ff0c1c1db2a3a654d7e5976c7
```

---

r? compiler

coverage: Re-land "Enlarge empty spans during MIR instrumentation"

This allows us to assume that coverage spans will only be discarded during codegen in very unusual situations.

---

This seemingly-simple change has a rather messy history:
- rust-lang#140847
- rust-lang#141650
- rust-lang#144298
- rust-lang#144480

Since then, a number of related changes have landed that should make it reasonable to try again:
- rust-lang#144530
- rust-lang#144560
- rust-lang#144616

In particular, we have multiple fixes/mitigations, and a confirmed regression test for the original bug that is not triggered by re-landing the changes in this PR.

Rollup merge of #144663 - Zalathar:empty-span, r=petrochenkov

coverage: Re-land "Enlarge empty spans during MIR instrumentation"

This allows us to assume that coverage spans will only be discarded during codegen in very unusual situations.

---

This seemingly-simple change has a rather messy history:
- #140847
- #141650
- #144298
- #144480

Since then, a number of related changes have landed that should make it reasonable to try again:
- #144530
- #144560
- #144616

In particular, we have multiple fixes/mitigations, and a confirmed regression test for the original bug that is not triggered by re-landing the changes in this PR.

coverage: Infer `instances_used` from `pgo_func_name_var_map`

In obscure circumstances involving macro-expanded spans, we would sometimes emit a covfun record for a function with no physical coverage counters, and therefore no corresponding entry in the “PGO names” section of the binary. The absence of that name entry causes `llvm-cov` to fail with the cryptic error message:

```text
malformed instrumentation profile data: function name is empty
```

We can eliminate this mismatch by removing `instances_used` entirely, and instead inferring its contents from the keys of `pgo_func_name_var_map`.

This makes it impossible for a "used" function to lack a PGO name entry.

---

This is an attempt to eliminate the cause of rust-lang/rust#141577 when re-landing changes like rust-lang/rust#144298 in the future.

I haven't been able to reproduce the underlying issue in an in-tree test, because the only known repro involves a non-trivial derive proc-macro that relies on `syn` and `proc-macro2`. But I have manually verified in a separate branch that this change would have prevented the reoccurrence of rust-lang/rust#141577 (comment).