[PATCH] D25321: Fix PR13910: Don't warn that __builtin_unreachable() is unreachable

[Alex Lorenz via cfe-commits]

arphaman updated this revision to Diff 73898.
arphaman marked an inline comment as done.
arphaman added a comment.

The updated patch uses Adrian's suggestion.


Repository:
  rL LLVM

https://reviews.llvm.org/D25321

Files:
  lib/Analysis/ReachableCode.cpp
  test/Sema/warn-unreachable.c


Index: test/Sema/warn-unreachable.c
===================================================================
--- test/Sema/warn-unreachable.c
+++ test/Sema/warn-unreachable.c
@@ -396,3 +396,40 @@
   else
     calledFun();
 }
+
+int pr13910_foo(int x) {
+  if (x == 1)
+    return 0;
+  else
+    return x;
+  __builtin_unreachable(); // expected no warning
+}
+
+int pr13910_bar(int x) {
+  switch (x) {
+  default:
+    return x + 1;
+  }
+  pr13910_foo(x); // expected-warning {{code will never be executed}}
+}
+
+int pr13910_bar2(int x) {
+  if (x == 1)
+    return 0;
+  else
+    return x;
+  pr13910_foo(x);          // expected-warning {{code will never be executed}}
+  __builtin_unreachable(); // expected no warning
+  pr13910_foo(x);          // expected-warning {{code will never be executed}}
+}
+
+void pr13910_noreturn() {
+  raze();
+  __builtin_unreachable(); // expected no warning
+}
+
+void pr13910_assert() {
+  myassert(0 && "unreachable");
+  return;
+  __builtin_unreachable(); // expected no warning
+}
Index: lib/Analysis/ReachableCode.cpp
===================================================================
--- lib/Analysis/ReachableCode.cpp
+++ lib/Analysis/ReachableCode.cpp
@@ -58,6 +58,14 @@
   return false;
 }
 
+static bool isBuiltinUnreachable(const Stmt *S) {
+  if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
+    if (const auto *FDecl = dyn_cast<FunctionDecl>(DRE->getDecl()))
+      return FDecl->getIdentifier() &&
+             FDecl->getBuiltinID() == Builtin::BI__builtin_unreachable;
+  return false;
+}
+
 static bool isDeadReturn(const CFGBlock *B, const Stmt *S) {
   // Look to see if the current control flow ends with a 'return', and see if
   // 'S' is a substatement. The 'return' may not be the last element in the
@@ -574,8 +582,7 @@
 
   if (isa<BreakStmt>(S)) {
     UK = reachable_code::UK_Break;
-  }
-  else if (isTrivialDoWhile(B, S)) {
+  } else if (isTrivialDoWhile(B, S) || isBuiltinUnreachable(S)) {
     return;
   }
   else if (isDeadReturn(B, S)) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D25321.73898.patch
Type: text/x-patch
Size: 2013 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20161007/f11feef4/attachment.bin>