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x86_64: fix block result value tracking

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This commit is contained in:
Jacob Young 2023-03-24 00:03:39 -04:00
parent 12c07fcf20
commit c604111e22
1 changed files with 26 additions and 38 deletions
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64
src/arch/x86_64/CodeGen.zig
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@ -1085,6 +1085,17 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
}
}
fn getValue(self: *Self, value: MCValue, inst: ?Air.Inst.Index) void {
const reg = switch (value) {
.register => |reg| reg,
.register_overflow => |ro| ro.reg,
else => return,
};
if (self.register_manager.isRegFree(reg)) {
self.register_manager.getRegAssumeFree(reg, inst);
}
}
fn freeValue(self: *Self, value: MCValue) void {
switch (value) {
.register => |reg| {
@ -1136,25 +1147,10 @@ fn finishAir(self: *Self, inst: Air.Inst.Index, result: MCValue, operands: [Live
log.debug("%{d} => {}", .{ inst, result });
const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
branch.inst_table.putAssumeCapacityNoClobber(inst, result);
// In some cases (such as bitcast), an operand
// may be the same MCValue as the result. If
// that operand died and was a register, it
// was freed by processDeath. We have to
// "re-allocate" the register.
switch (result) {
.register => |reg| {
if (self.register_manager.isRegFree(reg)) {
self.register_manager.getRegAssumeFree(reg, inst);
}
},
.register_overflow => |ro| {
if (self.register_manager.isRegFree(ro.reg)) {
self.register_manager.getRegAssumeFree(ro.reg, inst);
}
},
else => {},
}
// In some cases, an operand may be reused as the result.
// If that operand died and was a register, it was freed by
// processDeath, so we have to "re-allocate" the register.
self.getValue(result, inst);
} else switch (result) {
.none, .dead, .unreach => {},
else => unreachable, // Why didn't the result die?
@ -5609,14 +5605,14 @@ fn airBlock(self: *Self, inst: Air.Inst.Index) !void {
});
defer self.blocks.getPtr(inst).?.relocs.deinit(self.gpa);
const ty = self.air.typeOfIndex(inst);
const unused = !ty.hasRuntimeBitsIgnoreComptime() or self.liveness.isUnused(inst);
{
// Here we use `.none` to represent a null value so that the first break
// instruction will choose a MCValue for the block result and overwrite
// this field. Following break instructions will use that MCValue to put
// their block results.
const ty = self.air.typeOfIndex(inst);
const result: MCValue =
if (!ty.hasRuntimeBitsIgnoreComptime() or self.liveness.isUnused(inst)) .dead else .none;
const result: MCValue = if (unused) .dead else .none;
const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
branch.inst_table.putAssumeCapacityNoClobber(inst, result);
}
@ -5627,6 +5623,9 @@ fn airBlock(self: *Self, inst: Air.Inst.Index) !void {
try self.genBody(body);
for (self.blocks.getPtr(inst).?.relocs.items) |reloc| try self.performReloc(reloc);
const result = if (unused) .dead else self.getResolvedInstValue(inst).?.*;
self.getValue(result, inst);
self.finishAirBookkeeping();
}
@ -5837,25 +5836,14 @@ fn br(self: *Self, inst: Air.Inst.Index, block: Air.Inst.Index, operand: Air.Ins
switch (dst_mcv.*) {
.none => {
const result = result: {
if (!self.reuseOperand(inst, operand, 0, src_mcv)) {
const new_mcv = try self.allocRegOrMem(block, true);
try self.setRegOrMem(self.air.typeOfIndex(block), new_mcv, src_mcv);
break :result new_mcv;
}
if (self.reuseOperand(inst, operand, 0, src_mcv)) break :result src_mcv;
// the value is actually tracked with block, not inst
switch (src_mcv) {
.register => |reg| if (!self.register_manager.isRegFree(reg)) {
if (RegisterManager.indexOfRegIntoTracked(reg)) |index| {
self.register_manager.registers[index] = block;
}
},
.stack_offset => {},
else => unreachable,
}
break :result src_mcv;
const new_mcv = try self.allocRegOrMem(block, true);
try self.setRegOrMem(self.air.typeOfIndex(block), new_mcv, src_mcv);
break :result new_mcv;
};
dst_mcv.* = result;
self.freeValue(result);
},
else => try self.setRegOrMem(self.air.typeOfIndex(block), dst_mcv.*, src_mcv),
}