Prevent obscure and incorrect tail-call optimization.
In this instance we are generating the tail-call during legalizeDAG. The 2nd
floor call can't be a tail call because it clobbers %xmm1, which is defined by
the first floor call. The first floor call can't be a tail-call because it's
not in the tail position. The only reasonable way I could think to fix this
in a target-independent manner was to check for glue logic on the copy reg.
rdar://10930395
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151877 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4ad179e..d1ded33 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1589,6 +1589,11 @@
Copy->getOpcode() != ISD::FP_EXTEND)
return false;
+ // If anything is glued to the copy, then we can't safely perform a tail call.
+ if (Copy->getOpcode() == ISD::CopyToReg &&
+ Copy->getNumOperands() == 4)
+ return false;
+
bool HasRet = false;
for (SDNode::use_iterator UI = Copy->use_begin(), UE = Copy->use_end();
UI != UE; ++UI) {