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Sema: fix false negative detecting comptime const

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The code for detecting when a local const initialization expression
ended up being comptime-known gave up when it encountered dbg_stmt
instructions, but such instructions are not supposed to matter.
This commit is contained in:
Andrew Kelley 2022-03-24 17:44:37 -07:00
parent f5f5b9373d
commit 9a1d5001d4
1 changed files with 41 additions and 9 deletions
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50
src/Sema.zig
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@ -2731,17 +2731,49 @@ fn zirResolveInferredAlloc(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Com
// instructions from the block, replacing the inst_map entry
// corresponding to the ZIR alloc instruction with a constant
// decl_ref pointing at our new Decl.
// dbg_stmt instructions may be interspersed into this pattern
// which must be ignored.
if (block.instructions.items.len < 3) break :ct;
// zig fmt: off
const const_inst = block.instructions.items[block.instructions.items.len - 3];
const bitcast_inst = block.instructions.items[block.instructions.items.len - 2];
const store_inst = block.instructions.items[block.instructions.items.len - 1];
const air_tags = sema.air_instructions.items(.tag);
var search_index: usize = block.instructions.items.len;
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
if (air_tags[const_inst] != .constant) break :ct;
if (air_tags[bitcast_inst] != .bitcast ) break :ct;
if (air_tags[store_inst] != .store ) break :ct;
// zig fmt: on
const store_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt => continue,
.store => break candidate,
else => break :ct,
}
} else unreachable; // TODO shouldn't need this
const bitcast_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt => continue,
.bitcast => break candidate,
else => break :ct,
}
} else unreachable; // TODO shouldn't need this
const const_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt => continue,
.constant => break candidate,
else => break :ct,
}
} else unreachable; // TODO shouldn't need this
const store_op = air_datas[store_inst].bin_op;
const store_val = (try sema.resolveMaybeUndefVal(block, src, store_op.rhs)) orelse break :ct;
if (store_op.lhs != Air.indexToRef(bitcast_inst)) break :ct;