Perform sibcall in some cases when arguments are passes memory. Look for cases
where callee's arguments are already in the caller's own caller's stack and
they line up perfectly. e.g.
extern int foo(int a, int b, int c);
int bar(int a, int b, int c) {
return foo(a, b, c);
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95053 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index a8308b8..d05de21 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1807,6 +1807,10 @@
unsigned NumBytes = CCInfo.getNextStackOffset();
if (FuncIsMadeTailCallSafe(CallConv))
NumBytes = GetAlignedArgumentStackSize(NumBytes, DAG);
+ else if (isTailCall && !PerformTailCallOpt)
+ // This is a sibcall. The memory operands are available in caller's
+ // own caller's stack.
+ NumBytes = 0;
int FPDiff = 0;
if (isTailCall) {
@@ -1976,9 +1980,11 @@
int FI = 0;
// Do not flag preceeding copytoreg stuff together with the following stuff.
InFlag = SDValue();
- for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
- CCValAssign &VA = ArgLocs[i];
- if (!VA.isRegLoc()) {
+ if (PerformTailCallOpt) {
+ for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
+ CCValAssign &VA = ArgLocs[i];
+ if (VA.isRegLoc())
+ continue;
assert(VA.isMemLoc());
SDValue Arg = Outs[i].Val;
ISD::ArgFlagsTy Flags = Outs[i].Flags;
@@ -2259,11 +2265,14 @@
return false;
}
+
+ // Look for obvious safe cases to perform tail call optimization that does not
+ // requite ABI changes. This is what gcc calls sibcall.
+
// Do not tail call optimize vararg calls for now.
if (isVarArg)
return false;
- // Look for obvious safe cases to perform tail call optimization.
// If the callee takes no arguments then go on to check the results of the
// call.
if (!Outs.empty()) {
@@ -2273,8 +2282,42 @@
CCState CCInfo(CalleeCC, isVarArg, getTargetMachine(),
ArgLocs, *DAG.getContext());
CCInfo.AnalyzeCallOperands(Outs, CCAssignFnForNode(CalleeCC));
- if (CCInfo.getNextStackOffset())
- return false;
+ if (CCInfo.getNextStackOffset()) {
+ MachineFunction &MF = DAG.getMachineFunction();
+ if (MF.getInfo<X86MachineFunctionInfo>()->getBytesToPopOnReturn())
+ return false;
+ if (Subtarget->isTargetWin64())
+ // Win64 ABI has additional complications.
+ return false;
+
+ // Check if the arguments are already laid out in the right way as
+ // the caller's fixed stack objects.
+ MachineFrameInfo *MFI = MF.getFrameInfo();
+ for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
+ CCValAssign &VA = ArgLocs[i];
+ EVT RegVT = VA.getLocVT();
+ SDValue Arg = Outs[i].Val;
+ ISD::ArgFlagsTy Flags = Outs[i].Flags;
+ if (Flags.isByVal())
+ return false; // TODO
+ if (VA.getLocInfo() == CCValAssign::Indirect)
+ return false;
+ if (!VA.isRegLoc()) {
+ LoadSDNode *Ld = dyn_cast<LoadSDNode>(Arg);
+ if (!Ld)
+ return false;
+ SDValue Ptr = Ld->getBasePtr();
+ FrameIndexSDNode *FINode = dyn_cast<FrameIndexSDNode>(Ptr);
+ if (!FINode)
+ return false;
+ int FI = FINode->getIndex();
+ if (!MFI->isFixedObjectIndex(FI))
+ return false;
+ if (VA.getLocMemOffset() != MFI->getObjectOffset(FI))
+ return false;
+ }
+ }
+ }
}
// If the caller does not return a value, then this is obviously safe.