Merging r243461:

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r243461 | Matthew.Arsenault | 2015-07-28 14:29:14 -0400 (Tue, 28 Jul 2015) | 5 lines

AMDGPU: Fix crash if called function is a bitcast

getCalledFunction() is null, so this would crash. Replace
crash with an error on unsupported call.

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llvm-svn: 253227