Merging r228969:

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r228969 | hfinkel | 2015-02-12 14:43:52 -0800 (Thu, 12 Feb 2015) | 7 lines

[SDAG] Don't try to use FP_EXTEND/FP_ROUND for int<->fp promotions

The PowerPC backend has long promoted some floating-point vector operations
(such as select) to integer vector operations. Unfortunately, this behavior was
broken by r216555. When using FP_EXTEND/FP_ROUND for promotions, we must check
that both the old and new types are floating-point types. Otherwise, we must
use BITCAST as we did prior to r216555 for everything.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@228986 91177308-0d34-0410-b5e6-96231b3b80d8