Merging r195439:
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r195439 | kcc | 2013-11-22 02:30:39 -0800 (Fri, 22 Nov 2013) | 3 lines
Revert r195318 as it causes miscompilation (PR18029)
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@195478 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 0deb181..9df0232 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2665,15 +2665,21 @@
RegsToPass.push_back(std::make_pair(unsigned(X86::EBX),
DAG.getNode(X86ISD::GlobalBaseReg, SDLoc(), 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);
}
}