[PATCH] D16843: [Sema] Fix bug in TypeLocBuilder::pushImpl

[Akira Hatanaka via cfe-commits]

ahatanak added a comment.

OK, I now understand what you meant.

> How about the following?

> 

>   else if (LocalAlignment == 8) {

>     if (NumBytesAtAlign8 == 0) {

>       // We have not seen any 8-byte aligned element yet. There is no padding and we are either 4-byte

>       // aligned or 8-byte aligned depending on NumBytesAtAlign4.

>       // Add in 4 bytes padding if we are not 8-byte aligned including this element.

>       if ((LocalSize + NumBytesAtAlign4) % 8 != 0) {

>         memmove(&Buffer[Index - 4], &Buffer[Index], NumBytesAtAlign4);

>         Index -= 4;

>       }


If Capacity is not a multiple of 8, (LocalSize + NumBytesAtAlign4) % 8 doesn't tell you whether the new element will be 8-byte aligned. For example, if Capacity==36, NumBytesAtAlign4==4, and LocalSize==8, (LocalSize + NumBytesAtAlign4) equals 12 but padding is not needed as the new element can start at Index=24. Note that it's possible to have a Capacity that isn't a multiple of 8 by calling TypeLocBuilder::reserve. I think padding is needed if the new index (Index - LocalSize) is not a multiple of 8.


http://reviews.llvm.org/D16843