[coroutines] Handle spills before catchswitch

If we need to spill the result of the PHI instruction, we insert the spill after
all of the PHIs and EHPads, however, in a catchswitch block there is no
room to insert the spill. Make room by splitting away catchswitch into a separate
block.

Before the fix:

    catch.dispatch:
       %val = phi i32 [ 1, %if.then ], [ 2, %if.else ]
       %switch = catchswitch within none [label %catch] unwind label %cleanuppad

After:

    catch.dispatch:
       %val = phi i32 [ 1, %if.then ], [ 2, %if.else ]
       %tok = cleanuppad within none []
       ; spill goes here
       cleanupret from %tok unwind label %catch.dispatch.switch
    catch.dispatch.switch:
       %switch = catchswitch within none [label %catch] unwind label %cleanuppad

https://reviews.llvm.org/D31846

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303232 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 26 insertions, 2 deletions

diff --git a/lib/Transforms/Coroutines/CoroFrame.cpp b/lib/Transforms/Coroutines/CoroFrame.cpp
index 4480220f2cd..417d57f7625 100644
--- a/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -347,6 +347,27 @@ static StructType *buildFrameType(Function &F, coro::Shape &Shape,
   return FrameTy;
 }
 
+// We need to make room to insert a spill after initial PHIs, but before
+// catchswitch instruction. Placing it before violates the requirement that
+// catchswitch, like all other EHPads must be the first nonPHI in a block.
+//
+// Split away catchswitch into a separate block and insert in its place:
+//
+//   cleanuppad <InsertPt> cleanupret.
+//
+// cleanupret instruction will act as an insert point for the spill.
+static Instruction *splitBeforeCatchSwitch(CatchSwitchInst *CatchSwitch) {
+  BasicBlock *CurrentBlock = CatchSwitch->getParent();
+  BasicBlock *NewBlock = CurrentBlock->splitBasicBlock(CatchSwitch);
+  CurrentBlock->getTerminator()->eraseFromParent();
+
+  auto *CleanupPad =
+      CleanupPadInst::Create(CatchSwitch->getParentPad(), {}, "", CurrentBlock);
+  auto *CleanupRet =
+      CleanupReturnInst::Create(CleanupPad, NewBlock, CurrentBlock);
+  return CleanupRet;
+}
+
 // Replace all alloca and SSA values that are accessed across suspend points
 // with GetElementPointer from coroutine frame + loads and stores. Create an
 // AllocaSpillBB that will become the new entry block for the resume parts of
@@ -437,8 +458,11 @@ static Instruction *insertSpills(SpillInfo &Spills, coro::Shape &Shape) {
           InsertPt = NewBB->getTerminator();
         } else if (dyn_cast<PHINode>(CurrentValue)) {
           // Skip the PHINodes and EH pads instructions.
-          InsertPt =
-              &*cast<Instruction>(E.def())->getParent()->getFirstInsertionPt();
+          BasicBlock *DefBlock = cast<Instruction>(E.def())->getParent();
+          if (auto *CSI = dyn_cast<CatchSwitchInst>(DefBlock->getTerminator()))
+            InsertPt = splitBeforeCatchSwitch(CSI);
+          else
+            InsertPt = &*DefBlock->getFirstInsertionPt();
         } else {
           // For all other values, the spill is placed immediately after
           // the definition.