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spirv: add liveness checks

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When a result of a pure instruction is not used, it also does not need to
be generated. The other backends already implement these checks, they were
ignored in SPIR-V up until now. New instructions added in the future should
have these be implemented from the start.
This commit is contained in:
Robin Voetter
2022-11-26 17:37:13 +01:00
parent 39016948f0
commit 3c5ab4dd3d
1 changed files with 43 additions and 29 deletions
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72
src/codegen/spirv.zig
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@@ -703,7 +703,7 @@ pub const DeclGen = struct {
fn genInst(self: *DeclGen, inst: Air.Inst.Index) !void {
const air_tags = self.air.instructions.items(.tag);
const result_id = switch (air_tags[inst]) {
const maybe_result_id: ?IdRef = switch (air_tags[inst]) {
// zig fmt: off
.add, .addwrap => try self.airArithOp(inst, .OpFAdd, .OpIAdd, .OpIAdd),
.sub, .subwrap => try self.airArithOp(inst, .OpFSub, .OpISub, .OpISub),
@@ -717,7 +717,8 @@ pub const DeclGen = struct {
.bool_and => try self.airBinOpSimple(inst, .OpLogicalAnd),
.bool_or => try self.airBinOpSimple(inst, .OpLogicalOr),
.not => try self.airNot(inst),
.bitcast => try self.airBitcast(inst),
.not => try self.airNot(inst),
.cmp_eq => try self.airCmp(inst, .OpFOrdEqual, .OpLogicalEqual, .OpIEqual),
.cmp_neq => try self.airCmp(inst, .OpFOrdNotEqual, .OpLogicalNotEqual, .OpINotEqual),
@@ -728,10 +729,9 @@ pub const DeclGen = struct {
.arg => self.airArg(),
.alloc => try self.airAlloc(inst),
.block => (try self.airBlock(inst)) orelse return,
.block => try self.airBlock(inst),
.load => try self.airLoad(inst),
.bitcast => try self.airBitcast(inst),
.br => return self.airBr(inst),
.breakpoint => return,
.cond_br => return self.airCondBr(inst),
@@ -741,12 +741,13 @@ pub const DeclGen = struct {
.ret => return self.airRet(inst),
.store => return self.airStore(inst),
.unreach => return self.airUnreach(),
.assembly => (try self.airAssembly(inst)) orelse return,
.call => (try self.airCall(inst, .auto)) orelse return,
.call_always_tail => (try self.airCall(inst, .always_tail)) orelse return,
.call_never_tail => (try self.airCall(inst, .never_tail)) orelse return,
.call_never_inline => (try self.airCall(inst, .never_inline)) orelse return,
.assembly => try self.airAssembly(inst),
.call => try self.airCall(inst, .auto),
.call_always_tail => try self.airCall(inst, .always_tail),
.call_never_tail => try self.airCall(inst, .never_tail),
.call_never_inline => try self.airCall(inst, .never_inline),
.dbg_var_ptr => return,
.dbg_var_val => return,
@@ -757,10 +758,12 @@ pub const DeclGen = struct {
else => |tag| return self.todo("implement AIR tag {s}", .{@tagName(tag)}),
};
const result_id = maybe_result_id orelse return;
try self.inst_results.putNoClobber(self.gpa, inst, result_id);
}
fn airBinOpSimple(self: *DeclGen, inst: Air.Inst.Index, comptime opcode: Opcode) !IdRef {
fn airBinOpSimple(self: *DeclGen, inst: Air.Inst.Index, comptime opcode: Opcode) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const lhs_id = try self.resolve(bin_op.lhs);
const rhs_id = try self.resolve(bin_op.rhs);
@@ -781,7 +784,8 @@ pub const DeclGen = struct {
comptime fop: Opcode,
comptime sop: Opcode,
comptime uop: Opcode,
) !IdRef {
) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
// LHS and RHS are guaranteed to have the same type, and AIR guarantees
// the result to be the same as the LHS and RHS, which matches SPIR-V.
const ty = self.air.typeOfIndex(inst);
@@ -833,7 +837,8 @@ pub const DeclGen = struct {
return result_id.toRef();
}
fn airShuffle(self: *DeclGen, inst: Air.Inst.Index) !IdRef {
fn airShuffle(self: *DeclGen, inst: Air.Inst.Index) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const ty = self.air.typeOfIndex(inst);
const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
const extra = self.air.extraData(Air.Shuffle, ty_pl.payload).data;
@@ -868,7 +873,8 @@ pub const DeclGen = struct {
return result_id.toRef();
}
fn airCmp(self: *DeclGen, inst: Air.Inst.Index, comptime fop: Opcode, comptime sop: Opcode, comptime uop: Opcode) !IdRef {
fn airCmp(self: *DeclGen, inst: Air.Inst.Index, comptime fop: Opcode, comptime sop: Opcode, comptime uop: Opcode) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const lhs_id = try self.resolve(bin_op.lhs);
const rhs_id = try self.resolve(bin_op.rhs);
@@ -913,7 +919,22 @@ pub const DeclGen = struct {
return result_id.toRef();
}
fn airNot(self: *DeclGen, inst: Air.Inst.Index) !IdRef {
fn airBitcast(self: *DeclGen, inst: Air.Inst.Index) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const ty_op = self.air.instructions.items(.data)[inst].ty_op;
const operand_id = try self.resolve(ty_op.operand);
const result_id = self.spv.allocId();
const result_type_id = try self.resolveTypeId(Type.initTag(.bool));
try self.func.body.emit(self.spv.gpa, .OpBitcast, .{
.id_result_type = result_type_id,
.id_result = result_id,
.operand = operand_id,
});
return result_id.toRef();
}
fn airNot(self: *DeclGen, inst: Air.Inst.Index) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const ty_op = self.air.instructions.items(.data)[inst].ty_op;
const operand_id = try self.resolve(ty_op.operand);
const result_id = self.spv.allocId();
@@ -926,7 +947,8 @@ pub const DeclGen = struct {
return result_id.toRef();
}
fn airAlloc(self: *DeclGen, inst: Air.Inst.Index) !IdRef {
fn airAlloc(self: *DeclGen, inst: Air.Inst.Index) !?IdRef {
if (self.liveness.isUnused(inst)) return null;
const ty = self.air.typeOfIndex(inst);
const result_type_id = try self.resolveTypeId(ty);
const result_id = self.spv.allocId();
@@ -981,7 +1003,7 @@ pub const DeclGen = struct {
try self.beginSpvBlock(label_id);
// If this block didn't produce a value, simply return here.
if (!ty.hasRuntimeBits())
if (!ty.hasRuntimeBitsIgnoreComptime())
return null;
// Combine the result from the blocks using the Phi instruction.
@@ -1002,19 +1024,6 @@ pub const DeclGen = struct {
return result_id.toRef();
}
fn airBitcast(self: *DeclGen, inst: Air.Inst.Index) !IdRef {
const ty_op = self.air.instructions.items(.data)[inst].ty_op;
const operand_id = try self.resolve(ty_op.operand);
const result_id = self.spv.allocId();
const result_type_id = try self.resolveTypeId(Type.initTag(.bool));
try self.func.body.emit(self.spv.gpa, .OpBitcast, .{
.id_result_type = result_type_id,
.id_result = result_id,
.operand = operand_id,
});
return result_id.toRef();
}
fn airBr(self: *DeclGen, inst: Air.Inst.Index) !void {
const br = self.air.instructions.items(.data)[inst].br;
const block = self.blocks.get(br.block_inst).?;
@@ -1104,6 +1113,7 @@ pub const DeclGen = struct {
}
fn airRet(self: *DeclGen, inst: Air.Inst.Index) !void {
if (self.liveness.isUnused(inst)) return;
const operand = self.air.instructions.items(.data)[inst].un_op;
const operand_ty = self.air.typeOf(operand);
if (operand_ty.hasRuntimeBits()) {
@@ -1299,6 +1309,10 @@ pub const DeclGen = struct {
try self.func.body.emit(self.spv.gpa, .OpUnreachable, {});
}
if (self.liveness.isUnused(inst) or !return_type.hasRuntimeBitsIgnoreComptime()) {
return null;
}
return result_id.toRef();
}
};