From 73d4bb6676ab5730f8b3a7c20cf5fb8f856bdabb Mon Sep 17 00:00:00 2001
From: Duncan Sands <baldrick@free.fr>
Date: Thu, 22 Nov 2007 22:24:59 +0000
Subject: [PATCH] Turn invokes of nounwind functions into ordinary calls.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44280 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SimplifyCFG.cpp         | 50 ++++++++++++++++++-
 .../SimplifyCFG/2007-11-22-InvokeNoUnwind.ll  | 14 ++++++
 2 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/SimplifyCFG/2007-11-22-InvokeNoUnwind.ll

diff --git a/lib/Transforms/Scalar/SimplifyCFG.cpp b/lib/Transforms/Scalar/SimplifyCFG.cpp
index 74005757206..692a8af0a2a 100644
--- a/lib/Transforms/Scalar/SimplifyCFG.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFG.cpp
@@ -71,6 +71,28 @@ static void ChangeToUnreachable(Instruction *I) {
   }
 }
 
+/// ChangeToCall - Convert the specified invoke into a normal call.
+static void ChangeToCall(InvokeInst *II) {
+  BasicBlock *BB = II->getParent();
+  SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
+  CallInst *NewCall = new CallInst(II->getCalledValue(), Args.begin(),
+                                   Args.end(), "", II);
+  NewCall->takeName(II);
+  NewCall->setCallingConv(II->getCallingConv());
+  NewCall->setParamAttrs(II->getParamAttrs());
+  II->replaceAllUsesWith(NewCall);
+
+  // Follow the call by a branch to the normal destination.
+  new BranchInst(II->getNormalDest(), II);
+
+  // Update PHI nodes in the unwind destination
+  II->getUnwindDest()->removePredecessor(BB);
+  BB->getInstList().erase(II);
+
+  if (NewCall->use_empty())
+    BB->getInstList().erase(NewCall);
+}
+
 /// IsNoReturn - Return true if the specified call is to a no-return function.
 static bool IsNoReturn(const CallInst *CI) {
   if (const ParamAttrsList *Attrs = CI->getParamAttrs())
@@ -90,6 +112,25 @@ static bool IsNoReturn(const CallInst *CI) {
   return false;
 }
 
+/// IsNoUnwind - Return true if the specified invoke is to a no-unwind function.
+static bool IsNoUnwind(const InvokeInst *II) {
+  if (const ParamAttrsList *Attrs = II->getParamAttrs())
+    if (Attrs->paramHasAttr(0, ParamAttr::NoUnwind))
+      return true;
+  
+  if (const Function *Callee = II->getCalledFunction()) {
+    if (const ParamAttrsList *Attrs = Callee->getParamAttrs())
+      if (Attrs->paramHasAttr(0, ParamAttr::NoUnwind))
+        return true;
+  
+    const FunctionType *FT = Callee->getFunctionType();
+    if (const ParamAttrsList *Attrs = FT->getParamAttrs())
+      if (Attrs->paramHasAttr(0, ParamAttr::NoUnwind))
+        return true;
+  }
+  return false;
+}
+
 
 static bool MarkAliveBlocks(BasicBlock *BB,
                             SmallPtrSet<BasicBlock*, 128> &Reachable) {
@@ -106,7 +147,7 @@ static bool MarkAliveBlocks(BasicBlock *BB,
 
     // Do a quick scan of the basic block, turning any obviously unreachable
     // instructions into LLVM unreachable insts.  The instruction combining pass
-    // canonnicalizes unreachable insts into stores to null or undef.
+    // canonicalizes unreachable insts into stores to null or undef.
     for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
       if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
         if (IsNoReturn(CI)) {
@@ -131,6 +172,13 @@ static bool MarkAliveBlocks(BasicBlock *BB,
         }
     }
 
+    // Turn invokes that call 'nounwind' functions into ordinary calls.
+    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
+      if (IsNoUnwind(II)) {
+        ChangeToCall(II);
+        Changed = true;
+      }
+
     Changed |= ConstantFoldTerminator(BB);
     for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
       Worklist.push_back(*SI);
diff --git a/test/Transforms/SimplifyCFG/2007-11-22-InvokeNoUnwind.ll b/test/Transforms/SimplifyCFG/2007-11-22-InvokeNoUnwind.ll
new file mode 100644
index 00000000000..8e8ef43932b
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/2007-11-22-InvokeNoUnwind.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | not grep invoke
+
+declare i32 @func(i8*) nounwind
+
+define i32 @test() {
+	invoke i32 @func( i8* null ) nounwind
+			to label %Cont unwind label %Other		; <i32>:1 [#uses=0]
+
+Cont:		; preds = %0
+	ret i32 0
+
+Other:		; preds = %0
+	ret i32 1
+}