Dale and Evan suggested putting the "check for setjmp" much earlier in the

machine code generation. That's a good idea, so I made it so.

llvm-svn: 104655

1 files changed, 34 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 6d789a674cf..7e40cb9c640 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -25,6 +25,7 @@
 #include "llvm/Intrinsics.h"
 #include "llvm/IntrinsicInst.h"
 #include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
 #include "llvm/CodeGen/FastISel.h"
 #include "llvm/CodeGen/GCStrategy.h"
 #include "llvm/CodeGen/GCMetadata.h"
@@ -253,6 +254,39 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   done:;
   }
 
+  // Set a flag indicating if the machine function makes a call to setjmp /
+  // sigsetjmp (i.e., a function marked "returns_twice"). We'll use this to
+  // disable certain optimizations which cannot handle such control flows.
+  // 
+  // FIXME: This goes beyond the setjmp/sigsetjmp functions. We should check for
+  // the GCC "returns twice" attribute.
+  const Module *M = Fn.getParent();
+  const Function *SetJmp = M->getFunction("setjmp");
+  const Function *SigSetJmp = M->getFunction("sigsetjmp");
+  bool HasReturnsTwiceCall = false;
+
+  if (SetJmp || SigSetJmp) {
+    if (SetJmp && !SetJmp->use_empty())
+      for (Value::const_use_iterator
+             I = SetJmp->use_begin(), E = SetJmp->use_end(); I != E; ++I)
+        if (const CallInst *CI = dyn_cast<CallInst>(I))
+          if (CI->getParent()->getParent() == &Fn) {
+            HasReturnsTwiceCall = true;
+            break;
+          }
+
+    if (!HasReturnsTwiceCall && SigSetJmp && !SigSetJmp->use_empty())
+      for (Value::const_use_iterator
+             I = SigSetJmp->use_begin(), E = SigSetJmp->use_end(); I != E; ++I)
+        if (const CallInst *CI = dyn_cast<CallInst>(I))
+          if (CI->getParent()->getParent() == &Fn) {
+            HasReturnsTwiceCall = true;
+            break;
+          }
+
+    mf.setReturnsTwiceCall(HasReturnsTwiceCall);
+  }
+
   // Release function-specific state. SDB and CurDAG are already cleared
   // at this point.
   FuncInfo->clear();