On 31/08/16 16:35, Eric Botcazou wrote:
> Hi,
>
> this is a regression present on the mainline and 6 branch and introduced by:
>
> 2014-04-25 Jiong Wang <jiong.w...@arm.com>
>
> * config/arm/predicates.md (call_insn_operand): Add long_call check.
> * config/arm/arm.md (sibcall, sibcall_value): Force the address to
> reg for long_call.
> * config/arm/arm.c (arm_function_ok_for_sibcall): Remove long_call
> restriction.
>
> For a longcall, any sibcall becomes an indirect sibcall and therefore
> requires
> a register to hold the target address. Now if all the argument registers are
>
> taken, this register will be IP but, for APCS frames and VFP, IP can be used
> in the sibcall epilogue to restore the VFP registers, so the target address
> is
> overwritten and the call goes astray. Testcase attached, compile it with
> e.g.
> -mapcs-frame -mfloat-abi=soft -O -foptimize-sibling-calls -ffunction-sections
> and you'll see for arm-eabi:
>
> sub ip, fp, #36
> vldm ip!, {d8}
> sub sp, fp, #28
> ldmfd sp, {r4, r5, r6, r7, fp, sp, lr}
> bx ip
>
> The attached patch reinstates the restriction for APCS frames and VFP. This
> might be deemed a big hammer, but isn't a regression from earlier releases of
> the compiler and APCS frames are deprecated in any case (we still support
> them
> for VxWorks 6 but VxWorks 7 switched to AAPCS).
>
> Tested on ARM/VxWorks 6 and ARM/EABI, OK for mainline and 6 branch?
>
>
Since you're going to need a back-port there should be a PR filed for this.
> 2016-08-31 Eric Botcazou <ebotca...@adacore.com>
>
> * config/arm/arm.c (arm_function_ok_for_sibcall): Add back restriction
> for long calls with APCS frame and VFP.
>
>
> 2016-08-31 Eric Botcazou <ebotca...@adacore.com>
>
> * gcc.target/arm/vfp-longcall-apcs.c: New test.
>
Have you checked that this works with multi-lib dejagnu runs and on
hard-float systems? I doubt this will work in armhf-linux, for example.
R.
>
> p.diff
>
>
> Index: config/arm/arm.c
> ===================================================================
> --- config/arm/arm.c (revision 239888)
> +++ config/arm/arm.c (working copy)
> @@ -6773,6 +6773,14 @@ arm_function_ok_for_sibcall (tree decl, tree exp)
> if (TARGET_VXWORKS_RTP && flag_pic && decl && !targetm.binds_local_p
> (decl))
> return false;
>
> + /* ??? Cannot tail-call to long calls with APCS frame and VFP, because IP
> + may be used both as target of the call and base register for restoring
> + the VFP registers */
> + if (TARGET_APCS_FRAME && TARGET_ARM
> + && TARGET_HARD_FLOAT && TARGET_VFP
> + && decl && arm_is_long_call_p (decl))
> + return false;
> +
> /* If we are interworking and the function is not declared static
> then we can't tail-call it unless we know that it exists in this
> compilation unit (since it might be a Thumb routine). */
>
>
> vfp-longcall-apcs.c
>
>
> /* { dg-do run } */
> /* { dg-require-effective-target arm_vfp_ok } */
> /* { dg-options "-mapcs-frame -mfpu=vfp -mfloat-abi=softfp -O
> -foptimize-sibling-calls -ffunction-sections" } */
>
> extern void abort (void);
>
> static __attribute__((noclone, noinline, long_call))
> int foo (int a, int b, int c, int d, double i)
> {
> return a;
> }
>
> static __attribute__((noclone, noinline))
> double baz (double i)
> {
> return i;
> }
>
> static __attribute__((noclone, noinline))
> int bar (int a, int b, int c, int d, double i, double j)
> {
> double l = baz (i) * j;
> return foo (a, b, c, d, l);
> }
>
> int
> main (void)
> {
> if (bar (0, 0, 0, 0, 0.0, 0.0) != 0)
> abort ();
>
> return 0;
> }
>
