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| <h4 class="subsection">9.41.5 Opcodes</h4> |
| |
| <p><a name="index-V850-opcodes-1985"></a><a name="index-opcodes-for-V850-1986"></a><code>as</code> implements all the standard V850 opcodes. |
| |
| <p><code>as</code> also implements the following pseudo ops: |
| |
| |
| <a name="index-g_t_0040code_007bhi0_007d-pseudo_002dop_002c-V850-1987"></a> |
| <dl><dt><code>hi0()</code><dd>Computes the higher 16 bits of the given expression and stores it into |
| the immediate operand field of the given instruction. For example: |
| |
| <p>‘<samp><span class="samp">mulhi hi0(here - there), r5, r6</span></samp>’ |
| |
| <p>computes the difference between the address of labels 'here' and |
| 'there', takes the upper 16 bits of this difference, shifts it down 16 |
| bits and then multiplies it by the lower 16 bits in register 5, putting |
| the result into register 6. |
| |
| <p><a name="index-g_t_0040code_007blo_007d-pseudo_002dop_002c-V850-1988"></a><br><dt><code>lo()</code><dd>Computes the lower 16 bits of the given expression and stores it into |
| the immediate operand field of the given instruction. For example: |
| |
| <p>‘<samp><span class="samp">addi lo(here - there), r5, r6</span></samp>’ |
| |
| <p>computes the difference between the address of labels 'here' and |
| 'there', takes the lower 16 bits of this difference and adds it to |
| register 5, putting the result into register 6. |
| |
| <p><a name="index-g_t_0040code_007bhi_007d-pseudo_002dop_002c-V850-1989"></a><br><dt><code>hi()</code><dd>Computes the higher 16 bits of the given expression and then adds the |
| value of the most significant bit of the lower 16 bits of the expression |
| and stores the result into the immediate operand field of the given |
| instruction. For example the following code can be used to compute the |
| address of the label 'here' and store it into register 6: |
| |
| <p>‘<samp><span class="samp">movhi hi(here), r0, r6</span></samp>’ |
| ‘<samp><span class="samp">movea lo(here), r6, r6</span></samp>’ |
| |
| <p>The reason for this special behaviour is that movea performs a sign |
| extension on its immediate operand. So for example if the address of |
| 'here' was 0xFFFFFFFF then without the special behaviour of the hi() |
| pseudo-op the movhi instruction would put 0xFFFF0000 into r6, then the |
| movea instruction would takes its immediate operand, 0xFFFF, sign extend |
| it to 32 bits, 0xFFFFFFFF, and then add it into r6 giving 0xFFFEFFFF |
| which is wrong (the fifth nibble is E). With the hi() pseudo op adding |
| in the top bit of the lo() pseudo op, the movhi instruction actually |
| stores 0 into r6 (0xFFFF + 1 = 0x0000), so that the movea instruction |
| stores 0xFFFFFFFF into r6 - the right value. |
| |
| <p><a name="index-g_t_0040code_007bhilo_007d-pseudo_002dop_002c-V850-1990"></a><br><dt><code>hilo()</code><dd>Computes the 32 bit value of the given expression and stores it into |
| the immediate operand field of the given instruction (which must be a |
| mov instruction). For example: |
| |
| <p>‘<samp><span class="samp">mov hilo(here), r6</span></samp>’ |
| |
| <p>computes the absolute address of label 'here' and puts the result into |
| register 6. |
| |
| <p><a name="index-g_t_0040code_007bsdaoff_007d-pseudo_002dop_002c-V850-1991"></a><br><dt><code>sdaoff()</code><dd>Computes the offset of the named variable from the start of the Small |
| Data Area (whoes address is held in register 4, the GP register) and |
| stores the result as a 16 bit signed value in the immediate operand |
| field of the given instruction. For example: |
| |
| <p>‘<samp><span class="samp">ld.w sdaoff(_a_variable)[gp],r6</span></samp>’ |
| |
| <p>loads the contents of the location pointed to by the label '_a_variable' |
| into register 6, provided that the label is located somewhere within +/- |
| 32K of the address held in the GP register. [Note the linker assumes |
| that the GP register contains a fixed address set to the address of the |
| label called '__gp'. This can either be set up automatically by the |
| linker, or specifically set by using the ‘<samp><span class="samp">--defsym __gp=<value></span></samp>’ |
| command line option]. |
| |
| <p><a name="index-g_t_0040code_007btdaoff_007d-pseudo_002dop_002c-V850-1992"></a><br><dt><code>tdaoff()</code><dd>Computes the offset of the named variable from the start of the Tiny |
| Data Area (whoes address is held in register 30, the EP register) and |
| stores the result as a 4,5, 7 or 8 bit unsigned value in the immediate |
| operand field of the given instruction. For example: |
| |
| <p>‘<samp><span class="samp">sld.w tdaoff(_a_variable)[ep],r6</span></samp>’ |
| |
| <p>loads the contents of the location pointed to by the label '_a_variable' |
| into register 6, provided that the label is located somewhere within +256 |
| bytes of the address held in the EP register. [Note the linker assumes |
| that the EP register contains a fixed address set to the address of the |
| label called '__ep'. This can either be set up automatically by the |
| linker, or specifically set by using the ‘<samp><span class="samp">--defsym __ep=<value></span></samp>’ |
| command line option]. |
| |
| <p><a name="index-g_t_0040code_007bzdaoff_007d-pseudo_002dop_002c-V850-1993"></a><br><dt><code>zdaoff()</code><dd>Computes the offset of the named variable from address 0 and stores the |
| result as a 16 bit signed value in the immediate operand field of the |
| given instruction. For example: |
| |
| <p>‘<samp><span class="samp">movea zdaoff(_a_variable),zero,r6</span></samp>’ |
| |
| <p>puts the address of the label '_a_variable' into register 6, assuming |
| that the label is somewhere within the first 32K of memory. (Strictly |
| speaking it also possible to access the last 32K of memory as well, as |
| the offsets are signed). |
| |
| <p><a name="index-g_t_0040code_007bctoff_007d-pseudo_002dop_002c-V850-1994"></a><br><dt><code>ctoff()</code><dd>Computes the offset of the named variable from the start of the Call |
| Table Area (whoes address is helg in system register 20, the CTBP |
| register) and stores the result a 6 or 16 bit unsigned value in the |
| immediate field of then given instruction or piece of data. For |
| example: |
| |
| <p>‘<samp><span class="samp">callt ctoff(table_func1)</span></samp>’ |
| |
| <p>will put the call the function whoes address is held in the call table |
| at the location labeled 'table_func1'. |
| |
| <p><a name="index-g_t_0040code_007blongcall_007d-pseudo_002dop_002c-V850-1995"></a><br><dt><code>.longcall name</code><dd>Indicates that the following sequence of instructions is a long call |
| to function <code>name</code>. The linker will attempt to shorten this call |
| sequence if <code>name</code> is within a 22bit offset of the call. Only |
| valid if the <code>-mrelax</code> command line switch has been enabled. |
| |
| <p><a name="index-g_t_0040code_007blongjump_007d-pseudo_002dop_002c-V850-1996"></a><br><dt><code>.longjump name</code><dd>Indicates that the following sequence of instructions is a long jump |
| to label <code>name</code>. The linker will attempt to shorten this code |
| sequence if <code>name</code> is within a 22bit offset of the jump. Only |
| valid if the <code>-mrelax</code> command line switch has been enabled. |
| |
| </dl> |
| |
| <p>For information on the V850 instruction set, see <cite>V850 |
| Family 32-/16-Bit single-Chip Microcontroller Architecture Manual</cite> from NEC. |
| Ltd. |
| |
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