[clang] [llvm] [coverage] skipping code coverage for 'if constexpr' and 'if consteval' (PR #78033)

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Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>,
Hana =?utf-8?q?Dusíková?= <hanicka at hanicka.net>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/78033 at github.com>


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@@ -1700,43 +1776,119 @@ struct CounterCoverageMappingBuilder
     Visit(S->getSubStmt());
   }
 
+  void coverIfConsteval(const IfStmt *S) {
+    assert(S->isConsteval());
+
+    const auto *Then = S->getThen();
+    const auto *Else = S->getElse();
+
+    // It's better for llvm-cov to create a new region with same counter
+    // so line-coverage can be properly calculated for lines containing
+    // a skipped region (without it the line is marked uncovered)
+    const Counter ParentCount = getRegion().getCounter();
+
+    extendRegion(S);
+
+    if (S->isNegatedConsteval()) {
+      // ignore 'if consteval'
+      markSkipped(S->getIfLoc(), getStart(Then));
+      propagateCounts(ParentCount, Then);
+
+      if (Else) {
+        // ignore 'else <else>'
+        markSkipped(getEnd(Then), getEnd(Else));
+      }
+    } else {
+      assert(S->isNonNegatedConsteval());
+      // ignore 'if consteval <then> [else]'
+      markSkipped(S->getIfLoc(), Else ? getStart(Else) : getEnd(Then));
+
+      if (Else)
+        propagateCounts(ParentCount, Else);
+    }
+  }
+
+  void coverIfConstexpr(const IfStmt *S) {
+    assert(S->isConstexpr());
+
+    // evaluate constant condition...
+    const auto *E = cast<ConstantExpr>(S->getCond());
----------------
gkotheim wrote:

@hanickadot The assumption that the condition of an `if contexpr` must be castable to `ConstantExpr` seems to be incorrect, see [this counterexample](https://github.com/llvm/llvm-project/issues/78920#issuecomment-1916903277).

https://github.com/llvm/llvm-project/pull/78033