Validate calls to printf

[LU-JOHN]

Kernels with calls to __builtin_printf can produce calls to printf in SPIRV. Add support in spirv-val to validate parameters to vararg functions.

[CLAassistant]

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[alan-baker]

The only printfs I'm aware of are the extended instructions DebugPrintf from NonSemantic.DebugPrintf and printf from OpenCL.std.

This is checking OpFunctionCall for something named printf (which requires an OpName attached). SPIR-V has no way to declare a vararg function using OpFunction. This doesn't seem like the right way to map printf.

[LU-JOHN]

The only printfs I'm aware of are the extended instructions DebugPrintf from NonSemantic.DebugPrintf and printf from OpenCL.std.

This is checking OpFunctionCall for something named printf (which requires an OpName attached). SPIR-V has no way to declare a vararg function using OpFunction. This doesn't seem like the right way to map printf.

Thanks. I'll investigate mapping printf to the printf instruction from OpenCL.std.

[LU-JOHN]

This PR is not the right solution. Update llvm-spirvto use printf instruction from OpenCL.std.