Merging r214517:

Merging r214517:
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r214517 | uweigand | 2014-08-01 14:35:58 +0000 (Fri, 01 Aug 2014) | 8 lines

[PowerPC] PR20280 - Slots for byval parameters are not immutable

Found by inspection while looking at PR20280: code would mark slots
in the parameter save area where a byval parameter is passed as
"immutable".  This is not correct since code is allowed to modify
byval parameters in place in the parameter save area.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_35@223736 91177308-0d34-0410-b5e6-96231b3b80d8