On Thu, Jan 22, 2015 at 12:34:37PM -0500, David Malcolm wrote: > Much of the jit testsuite currently segfaults on i686, after > two in-process iterations. In odd-numbered iterations, > gcc_jit_context_compile generates correct code, but on > even-numbered iterations, the generated code trashes the > %ebx register, leading to SIGSEGV back at the call site when > setting up iteration 3. > > The root cause is due to missing state cleanup when repeatedly > invoking the compiler in-process. > > The issue manifests in emit-rtl.c:init_emit_regs, at > this initialization: > > if ((unsigned) PIC_OFFSET_TABLE_REGNUM != INVALID_REGNUM) > pic_offset_table_rtx = gen_raw_REG (Pmode, PIC_OFFSET_TABLE_REGNUM); > else > pic_offset_table_rtx = NULL_RTX; > > On 32-bit i386 fPIC the definition PIC_OFFSET_TABLE_REGNUM itself > depends on pic_offset_table_rtx, and hence the above initialization > code cycles between switching pic_offset_table_rtx from NULL to > non-NULL (on odd-numbered iterations), then switching it back from > non-NULL to NULL (on even-numbered iterations). In the latter case, > this leads to generated code that's supposedly "fPIC", but erroneously > doesn't bother saving %ebx. > > The simple fix is to set pic_offset_table_rtx to NULL_RTX before > testing PIC_OFFSET_TABLE_REGNUM (and thus making the else clause > redundant). A more involved fix might be for the JIT to only > initialize RTL once, but doing so seems higher risk. > > Tested with "make check-jit" on i686; with this, all testcases pass > (with the usual 5 in-process iterations). > > Bootstrap®rtest in progress. > > OK for trunk if it passes? > > gcc/ChangeLog: > PR 64722
Please use PR jit/64722 > * emit-rtl.c (init_emit_regs): Set pic_offset_table_rtx to > NULL_RTX before testing PIC_OFFSET_TABLE_REGNUM, since the > latter may be affected by the former (e.g. on i686). Just wanted to note that I've bootstrapped/regtested the same patch successfully on x86_64-linux and i686-linux. Jakub