Fix dynamic linking on PPC64.
Dynamic linking on PPC64 has had problems since we had to move the top-down
hazard-detection logic post-ra. For dynamic linking to work there needs to be
a nop placed after every call. It turns out that it is really hard to guarantee
that nothing will be placed in between the call (bl) and the nop during post-ra
scheduling. Previous attempts at fixing this by placing logic inside the
hazard detector only partially worked.
This is now fixed in a different way: call+nop codegen-only instructions. As far
as CodeGen is concerned the pair is now a single instruction and cannot be split.
This solution works much better than previous attempts.
The scoreboard hazard detector is also renamed to be more generic, there is currently
no cpu-specific logic in it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153816 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index bfa4df9..8357e8b 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -472,6 +472,7 @@
case PPCISD::EXTSW_32: return "PPCISD::EXTSW_32";
case PPCISD::STD_32: return "PPCISD::STD_32";
case PPCISD::CALL_SVR4: return "PPCISD::CALL_SVR4";
+ case PPCISD::CALL_NOP_SVR4: return "PPCISD::CALL_NOP_SVR4";
case PPCISD::CALL_Darwin: return "PPCISD::CALL_Darwin";
case PPCISD::NOP: return "PPCISD::NOP";
case PPCISD::MTCTR: return "PPCISD::MTCTR";
@@ -2813,9 +2814,6 @@
return DAG.getNode(PPCISD::TC_RETURN, dl, MVT::Other, &Ops[0], Ops.size());
}
- Chain = DAG.getNode(CallOpc, dl, NodeTys, &Ops[0], Ops.size());
- InFlag = Chain.getValue(1);
-
// Add a NOP immediately after the branch instruction when using the 64-bit
// SVR4 ABI. At link time, if caller and callee are in a different module and
// thus have a different TOC, the call will be replaced with a call to a stub
@@ -2824,8 +2822,9 @@
// which restores the TOC of the caller from the TOC save slot of the current
// stack frame. If caller and callee belong to the same module (and have the
// same TOC), the NOP will remain unchanged.
+
+ bool needsTOCRestore = false;
if (!isTailCall && PPCSubTarget.isSVR4ABI()&& PPCSubTarget.isPPC64()) {
- SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue);
if (CallOpc == PPCISD::BCTRL_SVR4) {
// This is a call through a function pointer.
// Restore the caller TOC from the save area into R2.
@@ -2836,14 +2835,22 @@
// since r2 is a reserved register (which prevents the register allocator
// from allocating it), resulting in an additional register being
// allocated and an unnecessary move instruction being generated.
- Chain = DAG.getNode(PPCISD::TOC_RESTORE, dl, VTs, Chain, InFlag);
- InFlag = Chain.getValue(1);
- } else {
+ needsTOCRestore = true;
+ } else if (CallOpc == PPCISD::CALL_SVR4) {
// Otherwise insert NOP.
- InFlag = DAG.getNode(PPCISD::NOP, dl, MVT::Glue, InFlag);
+ CallOpc = PPCISD::CALL_NOP_SVR4;
}
}
+ Chain = DAG.getNode(CallOpc, dl, NodeTys, &Ops[0], Ops.size());
+ InFlag = Chain.getValue(1);
+
+ if (needsTOCRestore) {
+ SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue);
+ Chain = DAG.getNode(PPCISD::TOC_RESTORE, dl, VTs, Chain, InFlag);
+ InFlag = Chain.getValue(1);
+ }
+
Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, true),
DAG.getIntPtrConstant(BytesCalleePops, true),
InFlag);