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Use some non-obvious arithmetic to try to avoid some NIR optimizations that hide a bug in the Intel compiler backend for Gfx12+ (Tigerlake and newer) GPUs. Basically, when NIR sees x = (gl_FrontFacing ? -1.0 : 1.0) * a; it converts it to x = gl_FrontFacing ? -a : a; This avoids the bad code generation for the (gl_FrontFacing ? -1.0 : 1.0) case. v2: Make this a separate test. Suggested by Marcin. Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com> Part-of: <!627>
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