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x86_64: refactor cond_br with canonicaliseBranches helper

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This commit is contained in:
Jakub Konka 2022-09-02 17:19:14 +02:00
parent c0e288c782
commit b9c31a8703
1 changed files with 2 additions and 64 deletions
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66
src/arch/x86_64/CodeGen.zig
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@ -4736,9 +4736,6 @@ fn airCondBr(self: *Self, inst: Air.Inst.Index) !void {
// that we can use all the code emitting abstractions. This is why at the bottom we
// assert that parent_branch.free_registers equals the saved_then_branch.free_registers
// rather than assigning it.
const parent_branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
try parent_branch.inst_table.ensureUnusedCapacity(self.gpa, else_branch.inst_table.count());
log.debug("Upper branches:", .{});
for (self.branch_stack.items) |bs| {
log.debug("{}", .{bs.fmtDebug()});
@ -4747,67 +4744,8 @@ fn airCondBr(self: *Self, inst: Air.Inst.Index) !void {
log.debug("Then branch: {}", .{then_branch.fmtDebug()});
log.debug("Else branch: {}", .{else_branch.fmtDebug()});
const else_slice = else_branch.inst_table.entries.slice();
const else_keys = else_slice.items(.key);
const else_values = else_slice.items(.value);
for (else_keys) |else_key, else_idx| {
const else_value = else_values[else_idx];
const canon_mcv = if (then_branch.inst_table.fetchSwapRemove(else_key)) |then_entry| blk: {
// The instruction's MCValue is overridden in both branches.
parent_branch.inst_table.putAssumeCapacity(else_key, then_entry.value);
if (else_value == .dead) {
assert(then_entry.value == .dead);
continue;
}
break :blk then_entry.value;
} else blk: {
if (else_value == .dead)
continue;
// The instruction is only overridden in the else branch.
var i: usize = self.branch_stack.items.len - 1;
while (true) {
i -= 1; // If this overflows, the question is: why wasn't the instruction marked dead?
if (self.branch_stack.items[i].inst_table.get(else_key)) |mcv| {
assert(mcv != .dead);
break :blk mcv;
}
}
};
log.debug("consolidating else_entry {d} {}=>{}", .{ else_key, else_value, canon_mcv });
// TODO make sure the destination stack offset / register does not already have something
// going on there.
try self.setRegOrMem(self.air.typeOfIndex(else_key), canon_mcv, else_value);
// TODO track the new register / stack allocation
}
try parent_branch.inst_table.ensureUnusedCapacity(self.gpa, then_branch.inst_table.count());
const then_slice = then_branch.inst_table.entries.slice();
const then_keys = then_slice.items(.key);
const then_values = then_slice.items(.value);
for (then_keys) |then_key, then_idx| {
const then_value = then_values[then_idx];
// We already deleted the items from this table that matched the else_branch.
// So these are all instructions that are only overridden in the then branch.
parent_branch.inst_table.putAssumeCapacity(then_key, then_value);
log.debug("then_value = {}", .{then_value});
if (then_value == .dead)
continue;
const parent_mcv = blk: {
log.debug("{d}", .{self.branch_stack.items.len});
var i: usize = self.branch_stack.items.len - 1;
while (true) {
i -= 1;
if (self.branch_stack.items[i].inst_table.get(then_key)) |mcv| {
assert(mcv != .dead);
break :blk mcv;
}
}
};
log.debug("consolidating then_entry {d} {}=>{}", .{ then_key, parent_mcv, then_value });
// TODO make sure the destination stack offset / register does not already have something
// going on there.
try self.setRegOrMem(self.air.typeOfIndex(then_key), parent_mcv, then_value);
// TODO track the new register / stack allocation
}
const parent_branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
try self.canonicaliseBranches(parent_branch, &then_branch, &else_branch);
// We already took care of pl_op.operand earlier, so we're going
// to pass .none here