Remove restriction that 'sret' must be on the first parameter
Remove restriction that 'sret' must be on the first parameter

On Windows, it is often applied to the second parameter, and the x86
backend is prepared to deal with sret appearing on any parameter.

Other backends assume it only appears on parameter zero, but those are
target-specific requirements, and not an IR-level rule.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@280951 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm