arphaman created this revision.
arphaman added reviewers: dblaikie, krememek.
arphaman added a subscriber: cfe-commits.
arphaman set the repository for this revision to rL LLVM.
This patch fixes the issue of clang emitting an unreachable warning when it
encounters unreachable `__builtin_unreachable()` statements. It detects
references to `__builtin_unreachable` and doesn't emit an unreachable warning
for them.
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 +58,15 @@
return false;
}
+static bool isBuiltinUnreachable(const CFGBlock *B, const Stmt *S) {
+ if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(S)) {
+ const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(DRE->getDecl());
+ return FDecl && 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 +583,7 @@
if (isa<BreakStmt>(S)) {
UK = reachable_code::UK_Break;
- }
- else if (isTrivialDoWhile(B, S)) {
+ } else if (isTrivialDoWhile(B, S) || isBuiltinUnreachable(B, S)) {
return;
}
else if (isDeadReturn(B, S)) {
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 +58,15 @@
return false;
}
+static bool isBuiltinUnreachable(const CFGBlock *B, const Stmt *S) {
+ if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(S)) {
+ const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(DRE->getDecl());
+ return FDecl && 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 +583,7 @@
if (isa<BreakStmt>(S)) {
UK = reachable_code::UK_Break;
- }
- else if (isTrivialDoWhile(B, S)) {
+ } else if (isTrivialDoWhile(B, S) || isBuiltinUnreachable(B, S)) {
return;
}
else if (isDeadReturn(B, S)) {
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