Author: dim
Date: Fri Nov 22 17:54:53 2013
New Revision: 258472
URL: http://svnweb.freebsd.org/changeset/base/258472
Log:
Revert r258455 for now, as it apparently causes miscompilation in some
situations. Until this is fully resolved, the X.org workaround in ports
still needs to take place.
Modified:
head/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp
Modified: head/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp
==============================================================================
--- head/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp Fri Nov 22
14:56:10 2013 (r258471)
+++ head/contrib/llvm/lib/Target/X86/X86ISelLowering.cpp Fri Nov 22
17:54:53 2013 (r258472)
@@ -2449,15 +2449,21 @@ X86TargetLowering::LowerCall(TargetLower
RegsToPass.push_back(std::make_pair(unsigned(X86::EBX),
DAG.getNode(X86ISD::GlobalBaseReg, DebugLoc(),
getPointerTy())));
} else {
- // If we are tail calling a global or external symbol in GOT pic mode, we
- // cannot use a direct jump, since that would make lazy dynamic linking
- // impossible (see PR15086). So pretend this is not a tail call, to
- // prevent the optimization to a jump.
+ // If we are tail calling and generating PIC/GOT style code load the
+ // address of the callee into ECX. The value in ecx is used as target of
+ // the tail jump. This is done to circumvent the ebx/callee-saved problem
+ // for tail calls on PIC/GOT architectures. Normally we would just put
the
+ // address of GOT into ebx and then call target@PLT. But for tail calls
+ // ebx would be restored (since ebx is callee saved) before jumping to
the
+ // target@PLT.
+
+ // Note: The actual moving to ECX is done further down.
GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
- if ((G && !G->getGlobal()->hasHiddenVisibility() &&
- !G->getGlobal()->hasProtectedVisibility()) ||
- isa<ExternalSymbolSDNode>(Callee))
- isTailCall = false;
+ if (G && !G->getGlobal()->hasHiddenVisibility() &&
+ !G->getGlobal()->hasProtectedVisibility())
+ Callee = LowerGlobalAddress(Callee, DAG);
+ else if (isa<ExternalSymbolSDNode>(Callee))
+ Callee = LowerExternalSymbol(Callee, DAG);
}
}
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