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

[Hana Dusíková via cfe-commits]

https://github.com/hanickadot created https://github.com/llvm/llvm-project/pull/80292

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

>From 84c3e120e04394d024851f30044de591cf1599e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hana=20Dusi=CC=81kova=CC=81?= <hanicka at hanicka.net>
Date: Thu, 1 Feb 2024 14:34:16 +0100
Subject: [PATCH] [coverage] fix crash in code coverage and `if constexpr` with
 `ExprWithCleanups`

---
 clang/lib/CodeGen/CoverageMappingGen.cpp | 16 +++++++++++--
 clang/test/CoverageMapping/if.cpp        | 29 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 8b5e6c4ad8272..6640fe6f41fd1 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -1808,12 +1808,24 @@ struct CounterCoverageMappingBuilder
     }
   }
 
+private:
+  static bool evaluateConstantCondition(const Expr *Condition) {
+    if (const auto *Expr = dyn_cast<ConstantExpr>(Condition))
+      return Expr->getResultAsAPSInt().getExtValue();
+
+    if (const auto *Expr = dyn_cast<ExprWithCleanups>(Condition))
+      return evaluateConstantCondition(Expr->getSubExpr()); // recursion
+
+    assert(false && "Unexpected node in 'if constexpr' condition");
+    return false;
+  }
+
+public:
   void coverIfConstexpr(const IfStmt *S) {
     assert(S->isConstexpr());
 
     // evaluate constant condition...
-    const auto *E = cast<ConstantExpr>(S->getCond());
-    const bool isTrue = E->getResultAsAPSInt().getExtValue();
+    const bool isTrue = evaluateConstantCondition(S->getCond());
 
     extendRegion(S);
 
diff --git a/clang/test/CoverageMapping/if.cpp b/clang/test/CoverageMapping/if.cpp
index 3045ffe43948c..4de1467aa7ee3 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);