[WinEHPrepare] Turn terminatepad into a cleanuppad + call + cleanupret

The MSVC doesn't really support exception specifications so let's just
turn these into cleanuppads.  Later, we might use terminatepad to more
efficiently encode the "noexcept"-ness of a function body.

llvm-svn: 247848

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index fefb444cea9..3eed086a40d 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -144,6 +144,7 @@ private:
                           Function &F);
   bool prepareExplicitEH(Function &F,
                          SmallVectorImpl<BasicBlock *> &EntryBlocks);
+  void replaceTerminatePadWithCleanup(Function &F);
   void colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks);
   void demotePHIsOnFunclets(Function &F);
   void demoteUsesBetweenFunclets(Function &F);
@@ -3206,6 +3207,44 @@ void llvm::calculateWinCXXEHStateNumbers(const Function *ParentFn,
     Num.processCallSite(None, ImmutableCallSite());
 }
 
+void WinEHPrepare::replaceTerminatePadWithCleanup(Function &F) {
+  if (Personality != EHPersonality::MSVC_CXX)
+    return;
+  for (BasicBlock &BB : F) {
+    Instruction *First = BB.getFirstNonPHI();
+    auto *TPI = dyn_cast<TerminatePadInst>(First);
+    if (!TPI)
+      continue;
+
+    if (TPI->getNumArgOperands() != 1)
+      report_fatal_error(
+          "Expected a unary terminatepad for MSVC C++ personalities!");
+
+    auto *TerminateFn = dyn_cast<Function>(TPI->getArgOperand(0));
+    if (!TerminateFn)
+      report_fatal_error("Function operand expected in terminatepad for MSVC "
+                         "C++ personalities!");
+
+    // Insert the cleanuppad instruction.
+    auto *CPI = CleanupPadInst::Create(
+        BB.getContext(), {}, Twine("terminatepad.for.", BB.getName()), &BB);
+
+    // Insert the call to the terminate instruction.
+    auto *CallTerminate = CallInst::Create(TerminateFn, {}, &BB);
+    CallTerminate->setDoesNotThrow();
+    CallTerminate->setDoesNotReturn();
+    CallTerminate->setCallingConv(TerminateFn->getCallingConv());
+
+    // Insert a new terminator for the cleanuppad using the same successor as
+    // the terminatepad.
+    CleanupReturnInst::Create(CPI, TPI->getUnwindDest(), &BB);
+
+    // Let's remove the terminatepad now that we've inserted the new
+    // instructions.
+    TPI->eraseFromParent();
+  }
+}
+
 void WinEHPrepare::colorFunclets(Function &F,
                                  SmallVectorImpl<BasicBlock *> &EntryBlocks) {
   SmallVector<std::pair<BasicBlock *, BasicBlock *>, 16> Worklist;
@@ -3560,6 +3599,8 @@ bool WinEHPrepare::prepareExplicitEH(
   // not.
   removeUnreachableBlocks(F);
 
+  replaceTerminatePadWithCleanup(F);
+
   // Determine which blocks are reachable from which funclet entries.
   colorFunclets(F, EntryBlocks);