SjLjEHPrepare: Fix the pass for swifterror arguments

We cannot leave the identity copies 'select true, arg, undef' that this pass
inserts for arguments to simplify handling of values on swifterror arguments.

swifterror arguments have restrictions on their uses.

rdar://30839288

llvm-svn: 297197

1 files changed, 22 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SjLjEHPrepare.cpp b/llvm/lib/CodeGen/SjLjEHPrepare.cpp
index 209bbe54ea2..76e4dc5457a 100644
--- a/llvm/lib/CodeGen/SjLjEHPrepare.cpp
+++ b/llvm/lib/CodeGen/SjLjEHPrepare.cpp
@@ -64,6 +64,7 @@ public:
 
 private:
   bool setupEntryBlockAndCallSites(Function &F);
+  bool undoSwiftErrorSelect(Function &F);
   void substituteLPadValues(LandingPadInst *LPI, Value *ExnVal, Value *SelVal);
   Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst *> LPads);
   void lowerIncomingArguments(Function &F);
@@ -458,6 +459,25 @@ bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) {
   return true;
 }
 
+bool SjLjEHPrepare::undoSwiftErrorSelect(Function &F) {
+  // We have inserted dummy copies 'select true, arg, undef' in the entry block
+  // for arguments to simplify this pass.
+  // swifterror arguments cannot be used in this way. Undo the select for the
+  // swifterror argument.
+  for (auto &AI : F.args()) {
+    if (AI.isSwiftError()) {
+      assert(AI.hasOneUse() && "Must have converted the argument to a select");
+      auto *Select = dyn_cast<SelectInst>(AI.use_begin()->getUser());
+      assert(Select && "There must be single select user");
+      auto *OrigSwiftError = cast<Argument>(Select->getTrueValue());
+      Select->replaceAllUsesWith(OrigSwiftError);
+      Select->eraseFromParent();
+      return true;
+    }
+  }
+  return false;
+}
+
 bool SjLjEHPrepare::runOnFunction(Function &F) {
   Module &M = *F.getParent();
   RegisterFn = M.getOrInsertFunction(
@@ -476,5 +496,7 @@ bool SjLjEHPrepare::runOnFunction(Function &F) {
   FuncCtxFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_functioncontext);
 
   bool Res = setupEntryBlockAndCallSites(F);
+  if (Res)
+    Res |= undoSwiftErrorSelect(F);
   return Res;
 }