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stage2 regalloc: track Inst instead of ?Inst in register mapping

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The information whether a register is allocated to an instruction is
already encoded in the free_registers "bitmap". Duplicating that
information in the registers map is unnecessary and may lead to
performance degradations.
This commit is contained in:
joachimschmidt557 2022-02-13 20:40:51 +01:00 committed by Jakub Konka
parent 5f50980880
commit f5068107cd
1 changed files with 10 additions and 9 deletions
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19
src/register_manager.zig
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@ -33,11 +33,12 @@ pub fn RegisterManager(
assert(callee_preserved_regs.len > 0); // see note above
return struct {
/// Tracks the AIR instruction allocated to every register or
/// `null` if no instruction is allocated to a register
/// Tracks the AIR instruction allocated to every register. If
/// no instruction is allocated to a register (i.e. the
/// register is free), the value in that slot is undefined.
///
/// The key must be canonical register.
registers: [callee_preserved_regs.len]?Air.Inst.Index = [_]?Air.Inst.Index{null} ** callee_preserved_regs.len,
registers: [callee_preserved_regs.len]Air.Inst.Index = undefined,
/// Tracks which registers are free (in which case the
/// corresponding bit is set to 1)
free_registers: FreeRegInt = math.maxInt(FreeRegInt),
@ -201,14 +202,14 @@ pub fn RegisterManager(
if (self.isRegFree(reg)) {
self.markRegUsed(reg);
} else {
const spilled_inst = self.registers[index].?;
const spilled_inst = self.registers[index];
try self.getFunction().spillInstruction(reg, spilled_inst);
}
self.registers[index] = inst;
} else {
// Don't track the register
if (!self.isRegFree(reg)) {
const spilled_inst = self.registers[index].?;
const spilled_inst = self.registers[index];
try self.getFunction().spillInstruction(reg, spilled_inst);
self.freeReg(reg);
}
@ -241,7 +242,7 @@ pub fn RegisterManager(
if (!self.isRegFree(reg)) {
// Move the instruction that was previously there to a
// stack allocation.
const spilled_inst = self.registers[index].?;
const spilled_inst = self.registers[index];
self.registers[index] = tracked_inst;
try self.getFunction().spillInstruction(reg, spilled_inst);
} else {
@ -251,7 +252,7 @@ pub fn RegisterManager(
if (!self.isRegFree(reg)) {
// Move the instruction that was previously there to a
// stack allocation.
const spilled_inst = self.registers[index].?;
const spilled_inst = self.registers[index];
try self.getFunction().spillInstruction(reg, spilled_inst);
self.freeReg(reg);
}
@ -265,7 +266,7 @@ pub fn RegisterManager(
const index = reg.allocIndex() orelse return;
self.markRegAllocated(reg);
assert(self.registers[index] == null);
assert(self.isRegFree(reg));
self.registers[index] = inst;
self.markRegUsed(reg);
}
@ -275,7 +276,7 @@ pub fn RegisterManager(
const index = reg.allocIndex() orelse return;
log.debug("freeing register {}", .{reg});
self.registers[index] = null;
self.registers[index] = undefined;
self.markRegFree(reg);
}
};