Commit 6f9428eb authored by Matt Turner's avatar Matt Turner

glsl: Implement usubBorrow() built-in for ARB_gpu_shader5.

i965 implements this with a single (multiple destination) instruction,
SUBB. Emitting SUBB directly from usubBorrow() would be ideal, but our
optimization passes don't know how to copy with expressions with
side-effects.

Radeon has an SUBB_UINT instruction that only generates the borrow
bit. I've chosen to go this route and implement usubBorrow() by doing the
subtraction and the borrow operations separately.
Reviewed-by: default avatarKenneth Graunke <kenneth@whitecape.org>
Reviewed-by: default avatarIan Romanick <ian.d.romanick@intel.com>
parent 6c125973
......@@ -532,6 +532,7 @@ private:
B2(ldexp)
B2(frexp)
B1(uaddCarry)
B1(usubBorrow)
#undef B0
#undef B1
#undef B2
......@@ -1954,6 +1955,12 @@ builtin_builder::create_builtins()
_uaddCarry(glsl_type::uvec3_type),
_uaddCarry(glsl_type::uvec4_type),
NULL);
add_function("usubBorrow",
_usubBorrow(glsl_type::uint_type),
_usubBorrow(glsl_type::uvec2_type),
_usubBorrow(glsl_type::uvec3_type),
_usubBorrow(glsl_type::uvec4_type),
NULL);
#undef F
#undef FI
#undef FIU
......@@ -3741,6 +3748,20 @@ builtin_builder::_uaddCarry(const glsl_type *type)
return sig;
}
ir_function_signature *
builtin_builder::_usubBorrow(const glsl_type *type)
{
ir_variable *x = in_var(type, "x");
ir_variable *y = in_var(type, "y");
ir_variable *borrow = out_var(type, "borrow");
MAKE_SIG(type, gpu_shader5, 3, x, y, borrow);
body.emit(assign(borrow, ir_builder::borrow(x, y)));
body.emit(ret(sub(x, y)));
return sig;
}
/** @} */
/******************************************************************************/
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment