microsoft/spirv_to_dxil: Support doubles

First, we need to lower alu to scalar so that all alu ops on doubles
only take one input. Then, we can use our new double lowering pass.

Reviewed-by: Enrico Galli <enrico.galli@intel.com>
Reviewed-by: Michael Tang <tangm@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10063>

src/microsoft/spirv_to_dxil/spirv_to_dxil.c

@@ -87,6 +87,10 @@ spirv_to_dxil(const uint32_t *words, size_t word_count,
    NIR_PASS_V(nir, nir_lower_var_copies);
    NIR_PASS_V(nir, nir_lower_io_arrays_to_elements_no_indirects, false);
 
+   NIR_PASS_V(nir, nir_lower_alu_to_scalar, NULL, NULL);
+   NIR_PASS_V(nir, nir_opt_dce);
+   NIR_PASS_V(nir, dxil_nir_lower_double_math);
+
    {
       bool progress;
       do