Allow all types of callee's to be tail called. But avoid automatic tailcall if the callee is a result of bitcast to avoid losing necessary zext / sext etc.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95195 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 284b984..495418d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4197,8 +4197,9 @@
///
/// This function only tests target-independent requirements.
static bool
-isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
+isInTailCallPosition(CallSite CS, Attributes CalleeRetAttr,
const TargetLowering &TLI) {
+ const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
@@ -4207,6 +4208,12 @@
// The block must end in a return statement or an unreachable.
if (!Ret && !isa<UnreachableInst>(Term)) return false;
+ // Unless we are explicitly forcing tailcall optimization do not tailcall if
+ // the called function is bitcast'ed. The analysis may not be entirely
+ // accurate.
+ if (!PerformTailCallOpt && isa<BitCastInst>(CS.getCalledValue()))
+ return false;
+
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
@@ -4348,9 +4355,7 @@
// Check if target-independent constraints permit a tail call here.
// Target-dependent constraints are checked within TLI.LowerCallTo.
if (isTailCall &&
- !isInTailCallPosition(CS.getInstruction(),
- CS.getAttributes().getRetAttributes(),
- TLI))
+ !isInTailCallPosition(CS, CS.getAttributes().getRetAttributes(), TLI))
isTailCall = false;
std::pair<SDValue,SDValue> Result =
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 6f710ec..9d6b5a3 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2269,7 +2269,6 @@
return false;
}
-
// Look for obvious safe cases to perform tail call optimization that does not
// requite ABI changes. This is what gcc calls sibcall.
@@ -2324,22 +2323,7 @@
}
}
- // If the caller does not return a value, then this is obviously safe.
- // This is one case where it's safe to perform this optimization even
- // if the return types do not match.
- const Type *CallerRetTy = CallerF->getReturnType();
- if (CallerRetTy->isVoidTy())
- return true;
-
- // If the return types match, then it's safe.
- // Don't tail call optimize recursive call.
- GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
- if (!G) return false; // FIXME: common external symbols?
- if (const Function *CalleeF = dyn_cast<Function>(G->getGlobal())) {
- const Type *CalleeRetTy = CalleeF->getReturnType();
- return CallerRetTy == CalleeRetTy;
- }
- return false;
+ return true;
}
FastISel *