1 files changed, 28 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index ebbcaeb..6582d24 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -525,19 +525,15 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
       F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
 }
 
-bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
-                                           const Instruction *I,
-                                           const ReturnInst *Ret,
-                                           const TargetLoweringBase &TLI) {
-  // If the block ends with a void return or unreachable, it doesn't matter
-  // what the call's return type is.
-  if (!Ret || Ret->getNumOperands() == 0) return true;
+bool llvm::attributesPermitTailCall(const Function *F, const Instruction *I,
+                                    const ReturnInst *Ret,
+                                    const TargetLoweringBase &TLI,
+                                    bool *AllowDifferingSizes) {
+  // ADS may be null, so don't write to it directly.
+  bool DummyADS;
+  bool &ADS = AllowDifferingSizes ? *AllowDifferingSizes : DummyADS;
+  ADS = true;
 
-  // If the return value is undef, it doesn't matter what the call's
-  // return type is.
-  if (isa<UndefValue>(Ret->getOperand(0))) return true;
-
-  // Make sure the attributes attached to each return are compatible.
   AttrBuilder CallerAttrs(F->getAttributes(),
                           AttributeSet::ReturnIndex);
   AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
@@ -548,19 +544,18 @@ bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
   CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
   CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
 
-  bool AllowDifferingSizes = true;
   if (CallerAttrs.contains(Attribute::ZExt)) {
     if (!CalleeAttrs.contains(Attribute::ZExt))
       return false;
 
-    AllowDifferingSizes = false;
+    ADS = false;
     CallerAttrs.removeAttribute(Attribute::ZExt);
     CalleeAttrs.removeAttribute(Attribute::ZExt);
   } else if (CallerAttrs.contains(Attribute::SExt)) {
     if (!CalleeAttrs.contains(Attribute::SExt))
       return false;
 
-    AllowDifferingSizes = false;
+    ADS = false;
     CallerAttrs.removeAttribute(Attribute::SExt);
     CalleeAttrs.removeAttribute(Attribute::SExt);
   }
@@ -568,7 +563,24 @@ bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
   // If they're still different, there's some facet we don't understand
   // (currently only "inreg", but in future who knows). It may be OK but the
   // only safe option is to reject the tail call.
-  if (CallerAttrs != CalleeAttrs)
+  return CallerAttrs == CalleeAttrs;
+}
+
+bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
+                                           const Instruction *I,
+                                           const ReturnInst *Ret,
+                                           const TargetLoweringBase &TLI) {
+  // If the block ends with a void return or unreachable, it doesn't matter
+  // what the call's return type is.
+  if (!Ret || Ret->getNumOperands() == 0) return true;
+
+  // If the return value is undef, it doesn't matter what the call's
+  // return type is.
+  if (isa<UndefValue>(Ret->getOperand(0))) return true;
+
+  // Make sure the attributes attached to each return are compatible.
+  bool AllowDifferingSizes;
+  if (!attributesPermitTailCall(F, I, Ret, TLI, &AllowDifferingSizes))
     return false;
 
   const Value *RetVal = Ret->getOperand(0), *CallVal = I;