Boost the power of phi node constant folding slightly: if all operands are the phi node itself or undef, then return undef. This logic already existed at a higher level so in practice it shouldn't make the slightest difference.  Note that this code could be replaced by a call to PN->hasConstantValue().  However since we bail out the moment we see a non-constant operand, it is more efficient to have a specialized version of that logic.
Boost the power of phi node constant folding slightly: if all
operands are the phi node itself or undef, then return undef.
This logic already existed at a higher level so in practice it
shouldn't make the slightest difference.  Note that this code
could be replaced by a call to PN->hasConstantValue().  However
since we bail out the moment we see a non-constant operand, it
is more efficient to have a specialized version of that logic.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@119041 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,dslab-epfl/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,chubbymaggie/asap,GPUOpen-Drivers/llvm,dslab-epfl/asap,chubbymaggie/asap,apple/swift-llvm,apple/swift-llvm,chubbymaggie/asap,llvm-mirror/llvm,llvm-mirror/llvm,dslab-epfl/asap,chubbymaggie/asap,llvm-mirror/llvm,dslab-epfl/asap,apple/swift-llvm,chubbymaggie/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,chubbymaggie/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm