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microsoft / hlsl-specs

HLSL Specifications
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Clarifications and alignment of vector truncations #301

Closed llvm-beanz closed 2 months ago

llvm-beanz commented 3 months ago

Previously the spec had allowed trunction conversions to produce cxvalues which enabled them to be used in output arguments. This is inconsistent with the DXC and FXC implementation, which disallows binding trunctions to output arguments.

The spec also previously did not allow trunction to scalar values. Initially that was excluded due to discussions around truncations and extensions of output arguments. Since DXC and FXC both disallow trunction in output arguments, it seems safe to support truncation to scalar here with a cooresponding warning.

This will allow the spec to more consistently align with the reference implementations.

This has no change to overload resolution except that a vector argument can be truncated to a scalar producing a Truncation, Truncation Promotion, or Truncation Conversion implicit conversion sequence.:

damyanp commented 3 months ago

can be truncated to a scalar producing a Trunctaion, Truncation Prootion

possible typos in description?