Do a very simple pass over every function we emit to infer whether we can
mark it nounwind based on whether it contains any non-nounwind calls.
<rdar://problem/8087431>
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110163 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 396ab4e..35664af 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -311,6 +311,19 @@
EmitStmt(FD->getBody());
}
+/// Tries to mark the given function nounwind based on the
+/// non-existence of any throwing calls within it. We believe this is
+/// lightweight enough to do at -O0.
+static void TryMarkNoThrow(llvm::Function *F) {
+ for (llvm::Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
+ for (llvm::BasicBlock::iterator
+ BI = FI->begin(), BE = FI->end(); BI != BE; ++BI)
+ if (llvm::CallInst *Call = dyn_cast<llvm::CallInst>(&*BI))
+ if (!Call->doesNotThrow())
+ return;
+ F->setDoesNotThrow(true);
+}
+
void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn) {
const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
@@ -369,6 +382,11 @@
// Emit the standard function epilogue.
FinishFunction(BodyRange.getEnd());
+
+ // If we haven't marked the function nothrow through other means, do
+ // a quick pass now to see if we can.
+ if (!CurFn->doesNotThrow())
+ TryMarkNoThrow(CurFn);
}
/// ContainsLabel - Return true if the statement contains a label in it. If