This fixes the assertion error
"sm4_generate_vsir_instr_expr Failed assertion: dst_type->e.numeric.type == HLSL_TYPE_BOOL"
which occurs when compiling the following HLSL shader using the ps_4_0 target profile:
uniform float4 x;
uniform bool b;
float4 main() : SV_Target
{
if (!b)
clip(x.x);
else
clip(x.y);
return x;
}
We're already using functions not made available through either
metal_common or metal_texture. This doesn't seem to be an issue for the
Metal shader runner, possibly because the "online" compiler includes the
required headers by default. In any case, including metal_stdlib should
make all of MSLib available.
MSL doesn't seem to have any special handling for undefined values,
differently from SPIR-V. Thus we just emit zeros.
UNDEF registers are sometimes created by the DXIL parser,
for example in sm6_parser_emit_composite_construct().
For an if block
if (cond)
{
<then_block>
}
else
{
<else_block>
}
We flatten it by first replacing any store instruction `v[[k]] = x`
in the then_block with the following:
1: load(v[[k]])
2: cond ? x : @1
3: v[[k]] = @2
Similarly, we replace any store instruction `v[[k]] = x` in the
else_block with the following:
1: load(v[[k]])
2: cond ? @1 : x
3: v[[k]] = @2
Then we can concatenate <then_block> and <else_block> together and
get rid of the if block.
