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C backend: implement signed trunc

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Emily Bellows 2021-10-29 21:04:54 -04:00 committed by Andrew Kelley
parent 1de6f9a267
commit 969bcb6a59
3 changed files with 14 additions and 4 deletions
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9
src/codegen/c.zig
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@ -1390,7 +1390,14 @@ fn airTrunc(f: *Function, inst: Air.Inst.Index) !CValue {
return local;
},
.signed => {
return f.fail("TODO: C backend: implement trunc for signed integers", .{});
const operand_ty = f.air.typeOf(ty_op.operand);
const c_bits = toCIntBits(operand_ty.intInfo(target).bits) orelse
return f.fail("TODO: C backend: implement integer types larger than 128 bits", .{});
const shift_rhs = c_bits - dest_bits;
try writer.print("(int{d}_t)((uint{d}_t)", .{ c_bits, c_bits });
try f.writeCValue(writer, operand);
try writer.print(" << {d}) >> {d};\n", .{ shift_rhs, shift_rhs });
return local;
},
}
}

2
test/behavior.zig
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@ -5,6 +5,7 @@ test {
_ = @import("behavior/basic.zig");
_ = @import("behavior/bool.zig");
_ = @import("behavior/if.zig");
_ = @import("behavior/truncate.zig");
if (builtin.object_format != .c) {
// Tests that pass for stage1 and stage2 but not the C backend.
@ -60,7 +61,6 @@ test {
_ = @import("behavior/switch.zig");
_ = @import("behavior/this.zig");
_ = @import("behavior/translate_c_macros.zig");
_ = @import("behavior/truncate.zig");
_ = @import("behavior/underscore.zig");
_ = @import("behavior/union.zig");
_ = @import("behavior/usingnamespace.zig");

7
test/behavior/basic.zig
View File

@ -27,8 +27,11 @@ test "truncate to non-power-of-two integers" {
try testTrunc(u32, u1, 0b10110, 0b0);
try testTrunc(u32, u2, 0b10101, 0b01);
try testTrunc(u32, u2, 0b10110, 0b10);
// TODO add test coverage for this!
// try testTrunc(i32, i3, -4, -4);
try testTrunc(i32, i5, -4, -4);
try testTrunc(i32, i5, 4, 4);
try testTrunc(i32, i5, -28, 4);
try testTrunc(i32, i5, 28, -4);
try testTrunc(i32, i5, std.math.maxInt(i32), -1);
}
fn testTrunc(comptime Big: type, comptime Little: type, big: Big, little: Little) !void {