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riscv64: Handle writes to the zero register sensibly in result bookkeeping.

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Alex Rønne Petersen 2024-11-02 08:59:14 +01:00
parent bf21e4f725
commit 199782edd1
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1 changed files with 8 additions and 1 deletions
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9
src/arch/riscv64/CodeGen.zig
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@ -1768,8 +1768,15 @@ fn finishAirBookkeeping(func: *Func) void {
fn finishAirResult(func: *Func, inst: Air.Inst.Index, result: MCValue) void { fn finishAirResult(func: *Func, inst: Air.Inst.Index, result: MCValue) void {
if (func.liveness.isUnused(inst)) switch (result) { if (func.liveness.isUnused(inst)) switch (result) {
.none, .dead, .unreach => {}, .none, .dead, .unreach => {},
else => unreachable, // Why didn't the result die? // Why didn't the result die?
.register => |r| if (r != .zero) unreachable,
else => unreachable,
} else { } else {
switch (result) {
.register => |r| if (r == .zero) unreachable, // Why did we discard a used result?
else => {},
}
tracking_log.debug("%{d} => {} (birth)", .{ inst, result }); tracking_log.debug("%{d} => {} (birth)", .{ inst, result });
func.inst_tracking.putAssumeCapacityNoClobber(inst, InstTracking.init(result)); func.inst_tracking.putAssumeCapacityNoClobber(inst, InstTracking.init(result));
// In some cases, an operand may be reused as the result. // In some cases, an operand may be reused as the result.