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

[Manman Ren via cfe-commits]

manmanren added a comment.

Hi Akira,

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;
      }
    } else {
      unsigned Padding = NumBytesAtAlign4 % 8;
      if (Padding == 0) { 
        if (LocalSize % 8 == 0) {
          // Everything is set: there's no padding and we don't need to add
          // any.
        } else {
          assert(LocalSize % 8 == 4);
          // No existing padding; add in 4 bytes padding
          memmove(&Buffer[Index - 4], &Buffer[Index], NumBytesAtAlign4);
          Index -= 4;
        }
      } else {
        assert(Padding == 4);
        if (LocalSize % 8 == 0) {
          // Everything is set: there's 4 bytes padding and we don't need
          // to add any.
        } else {
          assert(LocalSize % 8 == 4);
          // There are 4 bytes padding, but we don't need any; remove it.
          memmove(&Buffer[Index + 4], &Buffer[Index], NumBytesAtAlign4);
          Index += 4;
        }
      }
    }
    // Forget about any padding.
    NumBytesAtAlign4 = 0;
    NumBytesAtAlign8 += LocalSize;
  }

Note that the handling of NumBytesAtAlign8 != 0 is the same for LocalAlignment == 4 vs. LocalAlignment == 8.
Also mention in the commit message that the original code seems to assume LocalSize is a multiple of 8 when LocalAlignment is 8.

Cheers,
Manman


http://reviews.llvm.org/D16843