callc (sm4 - asm)

Conditionally calls a subroutine marked by where the label l# appears in the program.

callc{_z|_nz} src0.select_component, l#

Item	Description
src0	[in] The component on which to test the condition.
l#	[in] The label of the subroutine.

Remarks

When a ret is encountered, return execution to the instruction after this call.

The token format contains the offset of the corresponding label in the Shader as a convenience.

The following example shows the call instruction.

                ...
                callc_z  r1.y, l3 // if all bits in r0.x are 0, call l3
                callc_nz r2.z, l3 // if any bit in r0.x is nonzero, call l3
                ...
                ret
                label l3
                    ...
                    retc_nz r0.x
                    ...
                ret

Restrictions

• Subroutines can nest 32 deep.
• The return address stack is managed transparently by the implementation.
• If there are already 32 entries on the return address stack and a call is issued, the call is skipped over.
• There is no automatic parameter stack. The application can use an indexable temporary register array (x#[]) to manually implement a stack. However, the subroutine call return addresses are not visible and are orthogonal to any manual stack management done by the application.
• Indexing of the l# parameter is not permitted.
• The 32-bit register supplied by src0 is tested at a bit level. If any bit is nonzero, callc_nz will perform the call. If all bits are zero, callc_z will perform the call.
• Recursion is not permitted.

This instruction applies to the following shader stages:

Vertex Shader	Geometry Shader	Pixel Shader
x	x	x

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 5	yes
Shader Model 4.1	yes
Shader Model 4	yes
Shader Model 3 (DirectX HLSL)	no
Shader Model 2 (DirectX HLSL)	no
Shader Model 1 (DirectX HLSL)	no

Related topics

Shader Model 4 Assembly (DirectX HLSL)