On Tue, Sep 23, 2014 at 3:54 PM, Ilya Enkovich <enkovich....@gmail.com> wrote:
> Here is a patch which combines results of my and Vladimir's work on EBX > enabling. > > It works OK for SPEC2000 and SPEC2006 on -Ofast + LTO. It passes bootstrap > but there are few new failures in make check. > > gcc.target/i386/pic-1.c fails because it doesn't expect we can use EBX in > 32bit PIC mode > gcc.target/i386/pr55458.c fails due to the same reason > gcc.target/i386/pr23098.c fails because compiler fails to use float constant > as an immediate and loads it from GOT instead > > Do we have the final decision about having a sompiler flag to control > enabling of pseudo PIC register? I think we should have a possibility to use > fixed EBX at least until we make sure pseudo PIC doesn't harm debug info > generation. If we have such option then gcc.target/i386/pic-1.c and > gcc.target/i386/pr55458.c should be modified, otherwise these tests should be > removed. I think having this flag would be dangerous. In effect, this flag would be a hidden -ffixed-bx, with unwanted consequences on asm code that handles ebx. As an example, please see config/i386/cpuid.h - ATM, we handle ebx in a special way when __PIC__ is defined. With your patch, we will have to handle it in a special way when new flag is in effect, which is impossible, unless another compiler-generated define is emitted. So, I vote to change PIC reg to a pseudo unconditionally and adjust testsuite for all (expected) fall-out. Uros.
