Do not force indirect tailcall through fixed registers: eax, r11. Add support to allow loads to be folded to tail call instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98465 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 3fad8ad..4058885 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -349,17 +349,17 @@
return true;
}
-/// MoveBelowCallSeqStart - Replace CALLSEQ_START operand with load's chain
-/// operand and move load below the call's chain operand.
-static void MoveBelowCallSeqStart(SelectionDAG *CurDAG, SDValue Load,
- SDValue Call, SDValue CallSeqStart) {
+/// MoveBelowCallOrigChain - Replace the original chain operand of the call with
+/// load's chain operand and move load below the call's chain operand.
+static void MoveBelowOrigChain(SelectionDAG *CurDAG, SDValue Load,
+ SDValue Call, SDValue OrigChain) {
SmallVector<SDValue, 8> Ops;
- SDValue Chain = CallSeqStart.getOperand(0);
+ SDValue Chain = OrigChain.getOperand(0);
if (Chain.getNode() == Load.getNode())
Ops.push_back(Load.getOperand(0));
else {
assert(Chain.getOpcode() == ISD::TokenFactor &&
- "Unexpected CallSeqStart chain operand");
+ "Unexpected chain operand");
for (unsigned i = 0, e = Chain.getNumOperands(); i != e; ++i)
if (Chain.getOperand(i).getNode() == Load.getNode())
Ops.push_back(Load.getOperand(0));
@@ -371,9 +371,9 @@
Ops.clear();
Ops.push_back(NewChain);
}
- for (unsigned i = 1, e = CallSeqStart.getNumOperands(); i != e; ++i)
- Ops.push_back(CallSeqStart.getOperand(i));
- CurDAG->UpdateNodeOperands(CallSeqStart, &Ops[0], Ops.size());
+ for (unsigned i = 1, e = OrigChain.getNumOperands(); i != e; ++i)
+ Ops.push_back(OrigChain.getOperand(i));
+ CurDAG->UpdateNodeOperands(OrigChain, &Ops[0], Ops.size());
CurDAG->UpdateNodeOperands(Load, Call.getOperand(0),
Load.getOperand(1), Load.getOperand(2));
Ops.clear();
@@ -386,7 +386,9 @@
/// isCalleeLoad - Return true if call address is a load and it can be
/// moved below CALLSEQ_START and the chains leading up to the call.
/// Return the CALLSEQ_START by reference as a second output.
-static bool isCalleeLoad(SDValue Callee, SDValue &Chain) {
+/// In the case of a tail call, there isn't a callseq node between the call
+/// chain and the load.
+static bool isCalleeLoad(SDValue Callee, SDValue &Chain, bool HasCallSeq) {
if (Callee.getNode() == Chain.getNode() || !Callee.hasOneUse())
return false;
LoadSDNode *LD = dyn_cast<LoadSDNode>(Callee.getNode());
@@ -397,12 +399,14 @@
return false;
// Now let's find the callseq_start.
- while (Chain.getOpcode() != ISD::CALLSEQ_START) {
+ while (HasCallSeq && Chain.getOpcode() != ISD::CALLSEQ_START) {
if (!Chain.hasOneUse())
return false;
Chain = Chain.getOperand(0);
}
-
+
+ if (!Chain.getNumOperands())
+ return false;
if (Chain.getOperand(0).getNode() == Callee.getNode())
return true;
if (Chain.getOperand(0).getOpcode() == ISD::TokenFactor &&
@@ -420,7 +424,9 @@
E = CurDAG->allnodes_end(); I != E; ) {
SDNode *N = I++; // Preincrement iterator to avoid invalidation issues.
- if (OptLevel != CodeGenOpt::None && N->getOpcode() == X86ISD::CALL) {
+ if (OptLevel != CodeGenOpt::None &&
+ (N->getOpcode() == X86ISD::CALL ||
+ N->getOpcode() == X86ISD::TC_RETURN)) {
/// Also try moving call address load from outside callseq_start to just
/// before the call to allow it to be folded.
///
@@ -440,11 +446,12 @@
/// \ /
/// \ /
/// [CALL]
+ bool HasCallSeq = N->getOpcode() == X86ISD::CALL;
SDValue Chain = N->getOperand(0);
SDValue Load = N->getOperand(1);
- if (!isCalleeLoad(Load, Chain))
+ if (!isCalleeLoad(Load, Chain, HasCallSeq))
continue;
- MoveBelowCallSeqStart(CurDAG, Load, SDValue(N, 0), Chain);
+ MoveBelowOrigChain(CurDAG, Load, SDValue(N, 0), Chain);
++NumLoadMoved;
continue;
}