move inline assembly constant out into C code so it doesn't get out of range in a large function (#602)
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@ -159,16 +159,15 @@ static inline void *resolve_branch(uint16_t *inst) {
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// GCC produces horrible code for subtraction of pointers here, and it was bugging me
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static inline int8_t slot_diff(struct irq_handler_chain_slot *to, struct irq_handler_chain_slot *from) {
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static_assert(sizeof(struct irq_handler_chain_slot) == 12, "");
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int32_t result;
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int32_t result = 0xaaaa;
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// return (to - from);
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// note this implementation has limited range, but is fine for plenty more than -128->127 result
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asm (".syntax unified\n"
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"subs %1, %2\n"
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"adcs %1, %1\n" // * 2 (and + 1 if negative for rounding)
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"ldr %0, =0xaaaa\n"
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"muls %0, %1\n"
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"lsrs %0, 20\n"
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: "=l" (result), "+l" (to)
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: "+l" (result), "+l" (to)
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: "l" (from)
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:
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);
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