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| <h4 class="subsection">3.17.35 SH Options</h4> |
| |
| <p>These ‘<samp><span class="samp">-m</span></samp>’ options are defined for the SH implementations: |
| |
| <dl> |
| <dt><code>-m1</code><dd><a name="index-m1-1940"></a>Generate code for the SH1. |
| |
| <br><dt><code>-m2</code><dd><a name="index-m2-1941"></a>Generate code for the SH2. |
| |
| <br><dt><code>-m2e</code><dd>Generate code for the SH2e. |
| |
| <br><dt><code>-m2a-nofpu</code><dd><a name="index-m2a_002dnofpu-1942"></a>Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way |
| that the floating-point unit is not used. |
| |
| <br><dt><code>-m2a-single-only</code><dd><a name="index-m2a_002dsingle_002donly-1943"></a>Generate code for the SH2a-FPU, in such a way that no double-precision |
| floating point operations are used. |
| |
| <br><dt><code>-m2a-single</code><dd><a name="index-m2a_002dsingle-1944"></a>Generate code for the SH2a-FPU assuming the floating-point unit is in |
| single-precision mode by default. |
| |
| <br><dt><code>-m2a</code><dd><a name="index-m2a-1945"></a>Generate code for the SH2a-FPU assuming the floating-point unit is in |
| double-precision mode by default. |
| |
| <br><dt><code>-m3</code><dd><a name="index-m3-1946"></a>Generate code for the SH3. |
| |
| <br><dt><code>-m3e</code><dd><a name="index-m3e-1947"></a>Generate code for the SH3e. |
| |
| <br><dt><code>-m4-nofpu</code><dd><a name="index-m4_002dnofpu-1948"></a>Generate code for the SH4 without a floating-point unit. |
| |
| <br><dt><code>-m4-single-only</code><dd><a name="index-m4_002dsingle_002donly-1949"></a>Generate code for the SH4 with a floating-point unit that only |
| supports single-precision arithmetic. |
| |
| <br><dt><code>-m4-single</code><dd><a name="index-m4_002dsingle-1950"></a>Generate code for the SH4 assuming the floating-point unit is in |
| single-precision mode by default. |
| |
| <br><dt><code>-m4</code><dd><a name="index-m4-1951"></a>Generate code for the SH4. |
| |
| <br><dt><code>-m4a-nofpu</code><dd><a name="index-m4a_002dnofpu-1952"></a>Generate code for the SH4al-dsp, or for a SH4a in such a way that the |
| floating-point unit is not used. |
| |
| <br><dt><code>-m4a-single-only</code><dd><a name="index-m4a_002dsingle_002donly-1953"></a>Generate code for the SH4a, in such a way that no double-precision |
| floating point operations are used. |
| |
| <br><dt><code>-m4a-single</code><dd><a name="index-m4a_002dsingle-1954"></a>Generate code for the SH4a assuming the floating-point unit is in |
| single-precision mode by default. |
| |
| <br><dt><code>-m4a</code><dd><a name="index-m4a-1955"></a>Generate code for the SH4a. |
| |
| <br><dt><code>-m4al</code><dd><a name="index-m4al-1956"></a>Same as <samp><span class="option">-m4a-nofpu</span></samp>, except that it implicitly passes |
| <samp><span class="option">-dsp</span></samp> to the assembler. GCC doesn't generate any DSP |
| instructions at the moment. |
| |
| <br><dt><code>-mb</code><dd><a name="index-mb-1957"></a>Compile code for the processor in big endian mode. |
| |
| <br><dt><code>-ml</code><dd><a name="index-ml-1958"></a>Compile code for the processor in little endian mode. |
| |
| <br><dt><code>-mdalign</code><dd><a name="index-mdalign-1959"></a>Align doubles at 64-bit boundaries. Note that this changes the calling |
| conventions, and thus some functions from the standard C library will |
| not work unless you recompile it first with <samp><span class="option">-mdalign</span></samp>. |
| |
| <br><dt><code>-mrelax</code><dd><a name="index-mrelax-1960"></a>Shorten some address references at link time, when possible; uses the |
| linker option <samp><span class="option">-relax</span></samp>. |
| |
| <br><dt><code>-mbigtable</code><dd><a name="index-mbigtable-1961"></a>Use 32-bit offsets in <code>switch</code> tables. The default is to use |
| 16-bit offsets. |
| |
| <br><dt><code>-mbitops</code><dd><a name="index-mbitops-1962"></a>Enable the use of bit manipulation instructions on SH2A. |
| |
| <br><dt><code>-mfmovd</code><dd><a name="index-mfmovd-1963"></a>Enable the use of the instruction <code>fmovd</code>. Check <samp><span class="option">-mdalign</span></samp> for |
| alignment constraints. |
| |
| <br><dt><code>-mhitachi</code><dd><a name="index-mhitachi-1964"></a>Comply with the calling conventions defined by Renesas. |
| |
| <br><dt><code>-mrenesas</code><dd><a name="index-mhitachi-1965"></a>Comply with the calling conventions defined by Renesas. |
| |
| <br><dt><code>-mno-renesas</code><dd><a name="index-mhitachi-1966"></a>Comply with the calling conventions defined for GCC before the Renesas |
| conventions were available. This option is the default for all |
| targets of the SH toolchain except for ‘<samp><span class="samp">sh-symbianelf</span></samp>’. |
| |
| <br><dt><code>-mnomacsave</code><dd><a name="index-mnomacsave-1967"></a>Mark the <code>MAC</code> register as call-clobbered, even if |
| <samp><span class="option">-mhitachi</span></samp> is given. |
| |
| <br><dt><code>-mieee</code><dd><a name="index-mieee-1968"></a>Increase IEEE-compliance of floating-point code. |
| At the moment, this is equivalent to <samp><span class="option">-fno-finite-math-only</span></samp>. |
| When generating 16 bit SH opcodes, getting IEEE-conforming results for |
| comparisons of NANs / infinities incurs extra overhead in every |
| floating point comparison, therefore the default is set to |
| <samp><span class="option">-ffinite-math-only</span></samp>. |
| |
| <br><dt><code>-minline-ic_invalidate</code><dd><a name="index-minline_002dic_005finvalidate-1969"></a>Inline code to invalidate instruction cache entries after setting up |
| nested function trampolines. |
| This option has no effect if -musermode is in effect and the selected |
| code generation option (e.g. -m4) does not allow the use of the icbi |
| instruction. |
| If the selected code generation option does not allow the use of the icbi |
| instruction, and -musermode is not in effect, the inlined code will |
| manipulate the instruction cache address array directly with an associative |
| write. This not only requires privileged mode, but it will also |
| fail if the cache line had been mapped via the TLB and has become unmapped. |
| |
| <br><dt><code>-misize</code><dd><a name="index-misize-1970"></a>Dump instruction size and location in the assembly code. |
| |
| <br><dt><code>-mpadstruct</code><dd><a name="index-mpadstruct-1971"></a>This option is deprecated. It pads structures to multiple of 4 bytes, |
| which is incompatible with the SH ABI. |
| |
| <br><dt><code>-mspace</code><dd><a name="index-mspace-1972"></a>Optimize for space instead of speed. Implied by <samp><span class="option">-Os</span></samp>. |
| |
| <br><dt><code>-mprefergot</code><dd><a name="index-mprefergot-1973"></a>When generating position-independent code, emit function calls using |
| the Global Offset Table instead of the Procedure Linkage Table. |
| |
| <br><dt><code>-musermode</code><dd><a name="index-musermode-1974"></a>Don't generate privileged mode only code; implies -mno-inline-ic_invalidate |
| if the inlined code would not work in user mode. |
| This is the default when the target is <code>sh-*-linux*</code>. |
| |
| <br><dt><code>-multcost=</code><var>number</var><dd><a name="index-multcost_003d_0040var_007bnumber_007d-1975"></a>Set the cost to assume for a multiply insn. |
| |
| <br><dt><code>-mdiv=</code><var>strategy</var><dd><a name="index-mdiv_003d_0040var_007bstrategy_007d-1976"></a>Set the division strategy to use for SHmedia code. <var>strategy</var> must be |
| one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call, |
| inv:call2, inv:fp . |
| "fp" performs the operation in floating point. This has a very high latency, |
| but needs only a few instructions, so it might be a good choice if |
| your code has enough easily exploitable ILP to allow the compiler to |
| schedule the floating point instructions together with other instructions. |
| Division by zero causes a floating point exception. |
| "inv" uses integer operations to calculate the inverse of the divisor, |
| and then multiplies the dividend with the inverse. This strategy allows |
| cse and hoisting of the inverse calculation. Division by zero calculates |
| an unspecified result, but does not trap. |
| "inv:minlat" is a variant of "inv" where if no cse / hoisting opportunities |
| have been found, or if the entire operation has been hoisted to the same |
| place, the last stages of the inverse calculation are intertwined with the |
| final multiply to reduce the overall latency, at the expense of using a few |
| more instructions, and thus offering fewer scheduling opportunities with |
| other code. |
| "call" calls a library function that usually implements the inv:minlat |
| strategy. |
| This gives high code density for m5-*media-nofpu compilations. |
| "call2" uses a different entry point of the same library function, where it |
| assumes that a pointer to a lookup table has already been set up, which |
| exposes the pointer load to cse / code hoisting optimizations. |
| "inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm for initial |
| code generation, but if the code stays unoptimized, revert to the "call", |
| "call2", or "fp" strategies, respectively. Note that the |
| potentially-trapping side effect of division by zero is carried by a |
| separate instruction, so it is possible that all the integer instructions |
| are hoisted out, but the marker for the side effect stays where it is. |
| A recombination to fp operations or a call is not possible in that case. |
| "inv20u" and "inv20l" are variants of the "inv:minlat" strategy. In the case |
| that the inverse calculation was nor separated from the multiply, they speed |
| up division where the dividend fits into 20 bits (plus sign where applicable), |
| by inserting a test to skip a number of operations in this case; this test |
| slows down the case of larger dividends. inv20u assumes the case of a such |
| a small dividend to be unlikely, and inv20l assumes it to be likely. |
| |
| <br><dt><code>-mdivsi3_libfunc=</code><var>name</var><dd><a name="index-mdivsi3_005flibfunc_003d_0040var_007bname_007d-1977"></a>Set the name of the library function used for 32 bit signed division to |
| <var>name</var>. This only affect the name used in the call and inv:call |
| division strategies, and the compiler will still expect the same |
| sets of input/output/clobbered registers as if this option was not present. |
| |
| <br><dt><code>-mfixed-range=</code><var>register-range</var><dd><a name="index-mfixed_002drange-1978"></a>Generate code treating the given register range as fixed registers. |
| A fixed register is one that the register allocator can not use. This is |
| useful when compiling kernel code. A register range is specified as |
| two registers separated by a dash. Multiple register ranges can be |
| specified separated by a comma. |
| |
| <br><dt><code>-madjust-unroll</code><dd><a name="index-madjust_002dunroll-1979"></a>Throttle unrolling to avoid thrashing target registers. |
| This option only has an effect if the gcc code base supports the |
| TARGET_ADJUST_UNROLL_MAX target hook. |
| |
| <br><dt><code>-mindexed-addressing</code><dd><a name="index-mindexed_002daddressing-1980"></a>Enable the use of the indexed addressing mode for SHmedia32/SHcompact. |
| This is only safe if the hardware and/or OS implement 32 bit wrap-around |
| semantics for the indexed addressing mode. The architecture allows the |
| implementation of processors with 64 bit MMU, which the OS could use to |
| get 32 bit addressing, but since no current hardware implementation supports |
| this or any other way to make the indexed addressing mode safe to use in |
| the 32 bit ABI, the default is -mno-indexed-addressing. |
| |
| <br><dt><code>-mgettrcost=</code><var>number</var><dd><a name="index-mgettrcost_003d_0040var_007bnumber_007d-1981"></a>Set the cost assumed for the gettr instruction to <var>number</var>. |
| The default is 2 if <samp><span class="option">-mpt-fixed</span></samp> is in effect, 100 otherwise. |
| |
| <br><dt><code>-mpt-fixed</code><dd><a name="index-mpt_002dfixed-1982"></a>Assume pt* instructions won't trap. This will generally generate better |
| scheduled code, but is unsafe on current hardware. The current architecture |
| definition says that ptabs and ptrel trap when the target anded with 3 is 3. |
| This has the unintentional effect of making it unsafe to schedule ptabs / |
| ptrel before a branch, or hoist it out of a loop. For example, |
| __do_global_ctors, a part of libgcc that runs constructors at program |
| startup, calls functions in a list which is delimited by −1. With the |
| -mpt-fixed option, the ptabs will be done before testing against −1. |
| That means that all the constructors will be run a bit quicker, but when |
| the loop comes to the end of the list, the program crashes because ptabs |
| loads −1 into a target register. Since this option is unsafe for any |
| hardware implementing the current architecture specification, the default |
| is -mno-pt-fixed. Unless the user specifies a specific cost with |
| <samp><span class="option">-mgettrcost</span></samp>, -mno-pt-fixed also implies <samp><span class="option">-mgettrcost=100</span></samp>; |
| this deters register allocation using target registers for storing |
| ordinary integers. |
| |
| <br><dt><code>-minvalid-symbols</code><dd><a name="index-minvalid_002dsymbols-1983"></a>Assume symbols might be invalid. Ordinary function symbols generated by |
| the compiler will always be valid to load with movi/shori/ptabs or |
| movi/shori/ptrel, but with assembler and/or linker tricks it is possible |
| to generate symbols that will cause ptabs / ptrel to trap. |
| This option is only meaningful when <samp><span class="option">-mno-pt-fixed</span></samp> is in effect. |
| It will then prevent cross-basic-block cse, hoisting and most scheduling |
| of symbol loads. The default is <samp><span class="option">-mno-invalid-symbols</span></samp>. |
| |
| <br><dt><code>-mfdpic</code><dd><a name="index-fdpic-1984"></a>Generate code using the FDPIC ABI for uClinux, as documented at |
| <a href="http://www.codesourcery.com/public/docs/sh-fdpic/sh-fdpic-abi.txt">http://www.codesourcery.com/public/docs/sh-fdpic/sh-fdpic-abi.txt</a><!-- /@w -->. |
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