> Do you have any test cases? I'm pretty sure this works, at least in > the usual cases.
They're going to be hard to construct since they are sensitive to such things as the number of registers saved. > A wild guess says that you're doing this in Ada. It may be something > specific to the nested case then. It is in Ada, but I don't think the nested case is the cause of the particular problem I ran into (it does need to be fixed anyway, though, since it might bite later). I suspect the case we're running into is either the args to push or the registers saved. Here's a description of the miscompilation we saw: > Specifically, in Ada.Text_IO.Put_Line, we end up calling memcpy > with a buffer allocated using "alloca". The alloca result > is aligned to a multiple of 8, but the corresponding operation > on the stack pointer is eliminated because combine assumes > the stack is aligned already. > > Specifically, in the example below, the assignment to > Buffer (1 .. Ilen) is done through memcpy, but > memcpy overwrites the return address. > > From a-textio.adb, around line 1450: > > -- Now prepare the string with its terminator > > declare > Buffer : String (1 .. Ilen + 2); > Plen : size_t; > > begin > Buffer (1 .. Ilen) := Item (Istart .. Item'Last); > Buffer (Ilen + 1) := Character'Val (LM); When you look at the disassembled code, we saw an update to the stack pointer in the prologue of a number that wasn't a multiple of 8 (it was 36, if I remember correctly).
