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sema: improve codegen of for loop safety checks #25939

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merged 1 commit into from
Nov 16, 2025
+11 −2
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sema: improve codegen of for loop safety checks #25939

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13 changes: 11 additions & 2 deletions src/Sema.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -4548,6 +4548,9 @@ fn zirForLen(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.
// This argument is a range.
const range_start = try sema.resolveInst(zir_arg_pair[0]);
const range_end = try sema.resolveInst(zir_arg_pair[1]);
if (try sema.resolveDefinedValue(block, arg_src, range_start)) |start| {
if (try sema.valuesEqual(start, .zero_usize, .usize)) break :l range_end;
}
break :l try sema.analyzeArithmetic(block, .sub, range_end, range_start, arg_src, arg_src, arg_src, true);
};
const arg_len = try sema.coerce(block, .usize, arg_len_uncoerced, arg_src);
Expand Down Expand Up @@ -4611,12 +4614,18 @@ fn zirForLen(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.

// Now for the runtime checks.
if (any_runtime and block.wantSafety()) {
var ok: Air.Inst.Ref = .none;
for (runtime_arg_lens, 0..) |arg_len, i| {
if (arg_len == .none) continue;
if (i == len_idx) continue;
const ok = try block.addBinOp(.cmp_eq, len, arg_len);
try sema.addSafetyCheck(block, src, ok, .for_len_mismatch);
const eq = try block.addBinOp(.cmp_eq, len, arg_len);
ok = if (ok != .none)
try block.addBinOp(.bool_and, ok, eq)
else
eq;
}
if (ok != .none)
try sema.addSafetyCheck(block, src, ok, .for_len_mismatch);
}

return len;
Expand Down