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asm: Improve warnings for unreachable blocks

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gingerBill
2026-08-24 23:56:19 +01:00
parent 13394e8bcd
commit b1a81cf6f3
1 changed files with 26 additions and 9 deletions
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35
src/check_asm_cfg.cpp
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@@ -509,17 +509,34 @@ gb_internal void check_asm_cfg_analyse(AsmCtx *asm_ctx, AsmCfg *cfg, CheckerCont
}
}
}
{
auto block_is_targeted = slice_make<bool>(heap_allocator(), cfg->blocks.count);
defer (slice_free(&block_is_targeted, heap_allocator()));
// NOTE(bill): unreachable code
for (AsmBlock &block : cfg->blocks) {
if (block.reachable) {
continue;
for_array(bi, cfg->blocks) {
AstAsmInstruction *last = cfg->insts[cfg->blocks[bi].last];
AsmInstructionFacts *lf = last->facts;
if (lf != nullptr && lf->branch_target != nullptr) {
i32 t = asm_cfg_label_block_index(lf->branch_target);
if (0 <= t && t < cast(i32)cfg->blocks.count) {
block_is_targeted[t] = true;
}
}
}
AstAsmInstruction *first = cfg->insts[block.first];
if (block.first == block.last) {
warning(first->name, "The asm instruction is unreachable within this block");
} else {
warning(first->name, "The asm instructions are unreachable within this block");
// NOTE(bill): unreachable code
for_array(bi, cfg->blocks) {
AsmBlock const &block = cfg->blocks[bi];
if (block.reachable) {
continue;
}
AstAsmInstruction *first = cfg->insts[block.first];
char const *plural = (block.first == block.last) ? "instruction is" : "instructions are";
if (block_is_targeted[bi]) {
warning(first->name, "The asm %s unreachable: this block is only reached from code that is itself unreachable", plural);
} else {
warning(first->name, "The asm %s unreachable: no branch targets it and control cannot fall through from above (e.g. it follows an unconditional jump, return, or halt)", plural);
}
}
}