| Message ID | 54204387.5090105@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 22/09/14 16:43, Kugan wrote: > AArch64 has the same issue ARM had where the LR register was not used in > leaf functions. This was reported in > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017. In AArch64, this > test-case need to be added with more live ranges for the need for the > LR_REGNUM. i.e test-case in the PR needs additional loops up to r31 for > the case AArch64 to see this. > > The same fix (from the thread > https://gcc.gnu.org/ml/gcc-patches/2011-04/msg02191.html) which went > into ARM should apply to AArch64 as well. Regression tested on qemu for > aarch64-none-linux-gnu with no new regressions. Is this OK for trunk? This still be a partial fix. LR should be a caller-saved register free to use in case it's saved properly to across function call. I had a very similar patch to this sitting in my local tree and under various benchmark analysis. -- Jiong > > Thanks, > Kugan > > > gcc/ChangeLog: > > 2014-09-23 Kugan Vivekanandarajah <kuganv@linaro.org> > > * config/aarch64/aarch64.h (EPILOGUE_USES): Return true only after > epilogue_completed is true. >
On 23/09/14 01:58, Jiong Wang wrote: > On 22/09/14 16:43, Kugan wrote: > >> AArch64 has the same issue ARM had where the LR register was not used in >> leaf functions. This was reported in >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017. In AArch64, this >> test-case need to be added with more live ranges for the need for the >> LR_REGNUM. i.e test-case in the PR needs additional loops up to r31 for >> the case AArch64 to see this. >> >> The same fix (from the thread >> https://gcc.gnu.org/ml/gcc-patches/2011-04/msg02191.html) which went >> into ARM should apply to AArch64 as well. Regression tested on qemu for >> aarch64-none-linux-gnu with no new regressions. Is this OK for trunk? > This still be a partial fix. LR should be a caller-saved register free > to use in case it's saved properly to across function call. Indeed. This should be improved from the generic code. Right now, if a hard register is used in EPILOGUE_USES, it conflicts with all the live ranges till a call site kills. I think we should have this patch till the generic code can be improved. Thanks, Kugan > > I had a very similar patch to this sitting in my local tree and under > various benchmark analysis. > > -- Jiong >> >> Thanks, >> Kugan >> >> >> gcc/ChangeLog: >> >> 2014-09-23 Kugan Vivekanandarajah <kuganv@linaro.org> >> >> * config/aarch64/aarch64.h (EPILOGUE_USES): Return true only after >> epilogue_completed is true. >> > >
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h index db950da..b3e4585 100644 --- a/gcc/config/aarch64/aarch64.h +++ b/gcc/config/aarch64/aarch64.h @@ -309,7 +309,7 @@ extern unsigned long aarch64_tune_flags; considered live at the start of the called function. */ #define EPILOGUE_USES(REGNO) \ - ((REGNO) == LR_REGNUM) + (epilogue_completed && (REGNO) == LR_REGNUM) /* EXIT_IGNORE_STACK should be nonzero if, when returning from a function, the stack pointer does not matter. The value is tested only in