| … | |
… | |
| 101 | #else |
101 | #else |
| 102 | return 0; |
102 | return 0; |
| 103 | #endif |
103 | #endif |
| 104 | } |
104 | } |
| 105 | |
105 | |
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106 | =item ecb_inline |
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107 | |
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108 | This is not actually an attribute, but you use it like one. It expands |
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109 | either to C<static inline> or to just C<static>, if inline isn't |
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110 | supported. It should be used to declare functions that should be inlined, |
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111 | for code size or speed reasons. |
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112 | |
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113 | Example: inline this function, it surely will reduce codesize. |
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114 | |
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115 | ecb_inline int |
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116 | negmul (int a, int b) |
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117 | { |
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118 | return - (a * b); |
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119 | } |
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120 | |
| 106 | =item ecb_noinline |
121 | =item ecb_noinline |
| 107 | |
122 | |
| 108 | Prevent a function from being inlined - it might be optimised away, but |
123 | Prevent a function from being inlined - it might be optimised away, but |
| 109 | not inlined into other functions. This is useful if you know your function |
124 | not inlined into other functions. This is useful if you know your function |
| 110 | is rarely called and large enough for inlining not to be helpful. |
125 | is rarely called and large enough for inlining not to be helpful. |
| … | |
… | |
| 448 | C<ecb_mod> implements the mathematical modulo operation, which is missing |
463 | C<ecb_mod> implements the mathematical modulo operation, which is missing |
| 449 | in the language. |
464 | in the language. |
| 450 | |
465 | |
| 451 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
466 | C<n> must be strictly positive (i.e. C<< >= 1 >>), while C<m> must be |
| 452 | negatable, that is, both C<m> and C<-m> must be representable in its |
467 | negatable, that is, both C<m> and C<-m> must be representable in its |
| 453 | type (this typically includes the minimum signed integer value, the same |
468 | type (this typically excludes the minimum signed integer value, the same |
| 454 | limitation as for C</> and C<%> in C). |
469 | limitation as for C</> and C<%> in C). |
| 455 | |
470 | |
| 456 | Current GCC versions compile this into an efficient branchless sequence on |
471 | Current GCC versions compile this into an efficient branchless sequence on |
| 457 | many systems. |
472 | almost all CPUs. |
| 458 | |
473 | |
| 459 | For example, when you want to rotate forward through the members of an |
474 | For example, when you want to rotate forward through the members of an |
| 460 | array for increasing C<m> (which might be negative), then you should use |
475 | array for increasing C<m> (which might be negative), then you should use |
| 461 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
476 | C<ecb_mod>, as the C<%> operator might give either negative results, or |
| 462 | change direction for negative values: |
477 | change direction for negative values: |
