[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>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/78033 at github.com>


================
@@ -1700,43 +1777,116 @@ struct CounterCoverageMappingBuilder
     Visit(S->getSubStmt());
   }
 
+  void CoverIfConsteval(const IfStmt *S) {
+    assert(S->isConsteval());
+
+    const auto *Then = S->getThen();
+    const auto *Else = S->getElse();
+
+    // I'm using 'propagateCounts' later as new region is better and allows me
+    // to properly calculate line coverage in llvm-cov utility
+    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 = dyn_cast<ConstantExpr>(S->getCond());
+    assert(E != nullptr);
+    const bool isTrue = E->getResultAsAPSInt().getExtValue();
+
+    extendRegion(S);
+
+    const auto *Init = S->getInit();
+    const auto *Then = S->getThen();
+    const auto *Else = S->getElse();
+
+    // I'm using 'propagateCounts' later as new region is better and allows me
+    // to properly calculate line coverage in llvm-cov utility
+    const Counter ParentCount = getRegion().getCounter();
+
+    // ignore 'if constexpr ('
+    SourceLocation startOfSkipped = S->getIfLoc();
+
+    if (Init) {
+      // don't mark initialisation as ignored
+      markSkipped(startOfSkipped, getStart(Init));
+      propagateCounts(ParentCount, Init);
+      // ignore after initialisation: '; <condition>)'...
+      startOfSkipped = getEnd(Init);
+    }
+
+    if (isTrue) {
+      // ignore '<condition>)'
+      markSkipped(startOfSkipped, getStart(Then));
+      propagateCounts(ParentCount, Then);
+
+      if (Else)
+        // ignore 'else <else>'
+        markSkipped(getEnd(Then), getEnd(Else));
+    } else {
+      // ignore '<condition>) <then> [else]'
+      markSkipped(startOfSkipped, Else ? getStart(Else) : getEnd(Then));
+
+      if (Else) {
+        propagateCounts(ParentCount, Else);
+      }
+    }
+  }
+
   void VisitIfStmt(const IfStmt *S) {
+    // "if constexpr" and "if consteval" are not normal conditional statements,
+    // they should behave more like a preprocessor conditions
+    if (S->isConsteval())
+      return CoverIfConsteval(S);
+    else if (S->isConstexpr())
+      return CoverIfConstexpr(S);
----------------
cor3ntin wrote:

I like it but can we say something like "their discarded statement should be skipped" instead of "like a preprocessor condition"? 

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