Register preservation rules
---------------------------
-Register preservation rules match the ELF ABI calling sequence with the
-following differences:
-
---- For the sc instruction, differences with the ELF ABI ---
-=========== ============= ========================================
-r0 Volatile (System call number.)
-r3 Volatile (Parameter 1, and return value.)
-r4-r8 Volatile (Parameters 2-6.)
-cr0 Volatile (cr0.SO is the return error condition.)
-cr1, cr5-7 Nonvolatile
-lr Nonvolatile
-=========== ============= ========================================
-
---- For the scv 0 instruction, differences with the ELF ABI ---
-=========== ============= ========================================
-r0 Volatile (System call number.)
-r3 Volatile (Parameter 1, and return value.)
-r4-r8 Volatile (Parameters 2-6.)
-=========== ============= ========================================
+Register preservation rules match the ELF ABI calling sequence with some
+differences.
+
+For the sc instruction, the differences from the ELF ABI are as follows:
+
++--------------+--------------------+-----------------------------------------+
+| Register | Preservation Rules | Purpose |
++==============+====================+=========================================+
+| r0 | Volatile | (System call number.) |
++--------------+--------------------+-----------------------------------------+
+| r3 | Volatile | (Parameter 1, and return value.) |
++--------------+--------------------+-----------------------------------------+
+| r4-r8 | Volatile | (Parameters 2-6.) |
++--------------+--------------------+-----------------------------------------+
+| cr0 | Volatile | (cr0.SO is the return error condition.) |
++--------------+--------------------+-----------------------------------------+
+| cr1, cr5-7 | Nonvolatile | |
++--------------+--------------------+-----------------------------------------+
+| lr | Nonvolatile | |
++--------------+--------------------+-----------------------------------------+
+
+For the scv 0 instruction, the differences from the ELF ABI are as follows:
+
++--------------+--------------------+-----------------------------------------+
+| Register | Preservation Rules | Purpose |
++==============+====================+=========================================+
+| r0 | Volatile | (System call number.) |
++--------------+--------------------+-----------------------------------------+
+| r3 | Volatile | (Parameter 1, and return value.) |
++--------------+--------------------+-----------------------------------------+
+| r4-r8 | Volatile | (Parameters 2-6.) |
++--------------+--------------------+-----------------------------------------+
All floating point and vector data registers as well as control and status
registers are nonvolatile.