SH-4 Registers (Windows CE 5.0)

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The SH-4 has 16 general-purpose registers. The following table shows the roles assigned to these registers.

Register	Description
R0	Serves as a temporary register when expanding assembly language pseudo-instructions, and holds function return values. In addition, R0 serves as an implicit source or destination in byte and 16-bit operations. Not preserved.
R1-R3	Serve as temporary registers Not preserved
R4-R7	Hold the first four words of integer and non-scalar incoming arguments. The argument build area provides space into which R4 through R7 holding arguments may spill. Not preserved.
R8-R13	Serve as permanent registers Preserved
R14	Serves as the default frame pointer. Any other permanent register may serve as the frame pointer, and leaf routines may use a temporary register as the frame pointer. Preserved.
R15	Serves as the stack pointer or as a permanent register Preserved.

The SH-4 has two banks of 16 floating-point registers designated Bank0 and Bank1. This specification does not define the use of Bank1. This calling convention assigns the following roles to the SH-4 Bank0 floating-point registers.

Double-Precision Register	Single-Precision Register	Description
DR0	FR0 FR1	Hold function return values. DR0 is another name for FR0 and FR1 as a pair.
DR2	FR2-FR3	Serve as temporary registers. DR2 is another name for FR2 and FR3 as a pair. Not preserved
DR4-DR10	FR4-FR11	Hold single- or double-precision floating-point arguments. The argument build area also provides space into which floating-point registers holding arguments may spill.
DR12-DR14	FR12-FR15	Serve as permanent registers Preserved

The floating-point status control affects the behavior of some floating-point instructions. The section SH-4 Prolog and Epilog defines the use of the PR, SZ, and FR bits within prologs and epilogs.

See Also

SH-4 Stack Frame Layout | SH-4 Prolog and Epilog

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