[coverage] fix crash in code coverage and `if constexpr` with `ExprWithCleanups` (#80292)

Fixes https://github.com/llvm/llvm-project/issues/80285

(cherry picked from commit bfc6eaa26326e4d0d20d1f4a1f0064c6df0135bd)

2 files changed, 33 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 5eca00f..0c43317 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -1812,8 +1812,10 @@ struct CounterCoverageMappingBuilder
     assert(S->isConstexpr());
 
     // evaluate constant condition...
-    const auto *E = cast<ConstantExpr>(S->getCond());
-    const bool isTrue = E->getResultAsAPSInt().getExtValue();
+    const bool isTrue =
+        S->getCond()
+            ->EvaluateKnownConstInt(CVM.getCodeGenModule().getContext())
+            .getBoolValue();
 
     extendRegion(S);
 
diff --git a/clang/test/CoverageMapping/if.cpp b/clang/test/CoverageMapping/if.cpp
index 3045ffe..445cdfc 100644
--- a/clang/test/CoverageMapping/if.cpp
+++ b/clang/test/CoverageMapping/if.cpp
@@ -234,6 +234,35 @@ constexpr int check_macro_consteval_if_skipped(int i) {   // CHECK-NEXT: [[@LINE
   return i;
 }
 
+struct false_value {
+  constexpr operator bool() {
+    return false;
+  }
+};
+
+template <typename> struct dependable_false_value {
+  constexpr operator bool() {
+    return false;
+  }
+};
+
+// GH-80285
+void should_not_crash() {
+  if constexpr (false_value{}) { };
+}
+
+template <typename> void should_not_crash_dependable() {
+  if constexpr (dependable_false_value<int>{}) { };
+}
+
+void should_not_crash_with_template_instance() {
+  should_not_crash_dependable<int>();
+}
+
+void should_not_crash_with_requires_expr() {
+  if constexpr (requires {42;}) { };
+}
+
 int instantiate_consteval(int i) {
   i *= check_consteval_with_else_discarded_then(i);
   i *= check_notconsteval_with_else_discarded_else(i);