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>

llvm-svn: 110163

3 files changed, 33 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 396ab4e6d2b..35664af219b 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -311,6 +311,19 @@ void CodeGenFunction::EmitFunctionBody(FunctionArgList &Args) {
   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 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn) {
 
   // 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
diff --git a/clang/test/CodeGen/unwind-attr.c b/clang/test/CodeGen/unwind-attr.c
index ee3199d274d..7b34ae207e1 100644
--- a/clang/test/CodeGen/unwind-attr.c
+++ b/clang/test/CodeGen/unwind-attr.c
@@ -1,6 +1,16 @@
-// RUN: %clang_cc1 -fexceptions -emit-llvm -o - %s | grep "@foo()" | not grep nounwind
-// RUN: %clang_cc1 -emit-llvm -o - %s | grep "@foo()" | grep nounwind 
+// RUN: %clang_cc1 -fexceptions -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck -check-prefix NOEXC %s
 
-int foo(void) {
-  return 0;
+int opaque();
+
+// CHECK:       define [[INT:i.*]] @test0() {
+// CHECK-NOEXC: define [[INT:i.*]] @test0() nounwind {
+int test0(void) {
+  return opaque();
+}
+
+// <rdar://problem/8087431>: locally infer nounwind at -O0
+// CHECK:       define [[INT:i.*]] @test1() nounwind {
+// CHECK-NOEXC: define [[INT:i.*]] @test1() nounwind {
+int test1(void) {
 }
diff --git a/clang/test/CodeGenCXX/global-init.cpp b/clang/test/CodeGenCXX/global-init.cpp
index 07db598900c..210f2a6969b 100644
--- a/clang/test/CodeGenCXX/global-init.cpp
+++ b/clang/test/CodeGenCXX/global-init.cpp
@@ -36,7 +36,7 @@ namespace test1 {
   const int y = x - 1; // This gets deferred.
   const int z = ~y;    // This also gets deferred, but gets "undeferred" before y.
   int test() { return z; }
-// CHECK:      define i32 @_ZN5test14testEv() {
+// CHECK:      define i32 @_ZN5test14testEv()
 
   // All of these initializers end up delayed, so we check them later.
 }