Add `abi_size` parameter to read/writeTwosComplement

Big-int functions were updated to respect the provided abi_size, rather
than inferring a potentially incorrect abi_size implicitly.

In combination with the convention that any required padding bits are
added on the MSB end, this means that exotic integers can potentially
have a well-defined memory layout.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/value.zig b/src/value.zig
index 2018eb3df3..a3dd6501e4 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1046,7 +1046,8 @@ pub const Value = extern union {
                 var bigint_buffer: BigIntSpace = undefined;
                 const bigint = val.toBigInt(&bigint_buffer);
                 const bits = ty.intInfo(target).bits;
-                bigint.writeTwosComplement(buffer, bits, target.cpu.arch.endian());
+                const abi_size = ty.abiSize(target);
+                bigint.writeTwosComplement(buffer, bits, abi_size, target.cpu.arch.endian());
             },
             .Enum => {
                 var enum_buffer: Payload.U64 = undefined;
@@ -1054,7 +1055,8 @@ pub const Value = extern union {
                 var bigint_buffer: BigIntSpace = undefined;
                 const bigint = int_val.toBigInt(&bigint_buffer);
                 const bits = ty.intInfo(target).bits;
-                bigint.writeTwosComplement(buffer, bits, target.cpu.arch.endian());
+                const abi_size = ty.abiSize(target);
+                bigint.writeTwosComplement(buffer, bits, abi_size, target.cpu.arch.endian());
             },
             .Float => switch (ty.floatBits(target)) {
                 16 => return floatWriteToMemory(f16, val.toFloat(f16), target, buffer),
@@ -1096,8 +1098,9 @@ pub const Value = extern union {
                 const Limb = std.math.big.Limb;
                 const limb_count = (buffer.len + @sizeOf(Limb) - 1) / @sizeOf(Limb);
                 const limbs_buffer = try arena.alloc(Limb, limb_count);
+                const abi_size = ty.abiSize(target);
                 var bigint = BigIntMutable.init(limbs_buffer, 0);
-                bigint.readTwosComplement(buffer, int_info.bits, endian, int_info.signedness);
+                bigint.readTwosComplement(buffer, int_info.bits, abi_size, endian, int_info.signedness);
                 return fromBigInt(arena, bigint.toConst());
             },
             .Float => switch (ty.floatBits(target)) {