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wasm: saturating shift-left for unsigned integers

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Luuk de Gram 2022-06-16 20:22:14 +02:00
parent ce5d934f5f
commit 53831442ef
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1 changed files with 55 additions and 1 deletions
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56
src/arch/wasm/CodeGen.zig
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@ -1454,6 +1454,7 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
.rem => self.airBinOp(inst, .rem),
.shl => self.airWrapBinOp(inst, .shl),
.shl_exact => self.airBinOp(inst, .shl),
.shl_sat => self.airShlSat(inst),
.shr, .shr_exact => self.airBinOp(inst, .shr),
.xor => self.airBinOp(inst, .xor),
.max => self.airMaxMin(inst, .max),
@ -1588,7 +1589,6 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
.mul_sat,
.mod,
.assembly,
.shl_sat,
.ret_addr,
.frame_addr,
.bit_reverse,
@ -4988,3 +4988,57 @@ fn signedSat(self: *Self, lhs_operand: WValue, rhs_operand: WValue, ty: Type, op
return bin_result;
}
}
fn airShlSat(self: *Self, inst: Air.Inst.Index) InnerError!WValue {
if (self.liveness.isUnused(inst)) return WValue{ .none = {} };
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const ty = self.air.typeOfIndex(inst);
const int_info = ty.intInfo(self.target);
if (int_info.bits > 64) {
return self.fail("TODO: Saturating shifting left for integers with bitsize '{d}'", .{int_info.bits});
}
const lhs = try self.resolveInst(bin_op.lhs);
const rhs = try self.resolveInst(bin_op.rhs);
if (int_info.signedness == .signed) {}
const wasm_bits = toWasmBits(int_info.bits).?;
const result = try self.allocLocal(ty);
if (wasm_bits == int_info.bits) {
const shl = try self.binOp(lhs, rhs, ty, .shl);
const shr = try self.binOp(shl, rhs, ty, .shr);
const cmp_result = try self.cmp(lhs, shr, ty, .neq);
if (wasm_bits == 32)
try self.addImm32(-1)
else
try self.addImm64(@bitCast(u64, @as(i64, -1)));
try self.emitWValue(shl);
try self.emitWValue(cmp_result);
try self.addTag(.select);
try self.addLabel(.local_set, result.local);
return result;
} else {
const shift_size = wasm_bits - int_info.bits;
const shift_value = switch (wasm_bits) {
32 => WValue{ .imm32 = shift_size },
64 => WValue{ .imm64 = shift_size },
else => unreachable,
};
const shl_res = try self.binOp(lhs, shift_value, ty, .shl);
const shl = try self.binOp(shl_res, rhs, ty, .shl);
const shr = try self.binOp(shl, rhs, ty, .shr);
const cmp_result = try self.cmp(shl_res, shr, ty, .neq);
if (wasm_bits == 32)
try self.addImm32(-1)
else
try self.addImm64(@bitCast(u64, @as(i64, -1)));
try self.emitWValue(shl);
try self.emitWValue(cmp_result);
try self.addTag(.select);
try self.addLabel(.local_set, result.local);
return self.binOp(result, shift_value, ty, .shr);
}
}