[ArgumentPromotion] don't break musttail invariant PR36543

Summary:
Do not break musttail invariant by promoting arguments of musttail
callee or caller.

Reviewers: sanjoy, dberlin, hfinkel, george.burgess.iv, fhahn, rnk

Reviewed By: rnk

Subscribers: rnk, llvm-commits

Differential Revision: https://reviews.llvm.org/D43926

llvm-svn: 326521

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
index 461c4e12cbd..d27adca86f2 100644
--- a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -853,10 +853,20 @@ promoteArguments(Function *F, function_ref<AAResults &(Function &F)> AARGetter,
     if (CS.getInstruction() == nullptr || !CS.isCallee(&U))
       return nullptr;
 
+    // Can't change signature of musttail callee
+    if (CS.isMustTailCall())
+      return nullptr;
+
     if (CS.getInstruction()->getParent()->getParent() == F)
       isSelfRecursive = true;
   }
 
+  // Can't change signature of musttail caller
+  // FIXME: Support promoting whole chain of musttail functions
+  for (BasicBlock &BB : *F)
+    if (BB.getTerminatingMustTailCall())
+      return nullptr;
+
   const DataLayout &DL = F->getParent()->getDataLayout();
 
   AAResults &AAR = AARGetter(*F);