Rollup merge of #80521 - richkadel:llvm-coverage-counters-2.4.0, r=wesleywiser

MIR Inline is incompatible with coverage

Fixes: #80060

Fixed by disabling inlining if `-Zinstrument-coverage` is set.

The PR also adds additional use cases to the coverage test for doctests.

r? `@wesleywiser`
cc: `@tmandry`

compiler/rustc_mir/src/transform/inline.rs

@@ -41,6 +41,15 @@ impl<'tcx> MirPass<'tcx> for Inline {
             return;
         }
 
+        if tcx.sess.opts.debugging_opts.instrument_coverage {
+            // Since `Inline` happens after `InstrumentCoverage`, the function-specific coverage
+            // counters can be invalidated, such as by merging coverage counter statements from
+            // a pre-inlined function into a different function. This kind of change is invalid,
+            // so inlining must be skipped. Note: This check is performed here so inlining can
+            // be disabled without preventing other optimizations (regardless of `mir_opt_level`).
+            return;
+        }
+
         if inline(tcx, body) {
             debug!("running simplify cfg on {:?}", body.source);
             CfgSimplifier::new(body).simplify();