Re: [patch, ARM] ICE in get_arm_condition_code()

[Chung-Lin Tang <cltang at codesourcery dot com>]

Ping.
(I'll fix the minor nits before actually committing, thanks Ramana :)

On 2011/1/13 08:24, Chung-Lin Tang wrote:
> Hi,
> there's an ICE in arm.c:get_arm_condition_code(), from here:
> https://bugs.launchpad.net/gcc-linaro/+bug/689887
> 
> The report was on a 4.5 based compiler, but I verified it also occurs on
> current trunk, under Thumb-2.
> 
> The problem as I found, happens in RTL ifcvt after the combine pass.
> ifcvt.c:noce_emit_cmove() creates this:
> (insn 58 57 59 4 (parallel [
>             (set (reg:CC_NCV 24 cc)
>                 (compare:CC_NCV (reg:DI 140)
>                     (reg:DI 147)))
>             (clobber (scratch:SI))
>         ]) p.c:13 202 {*arm_cmpdi_insn}
>      (nil))
> 
> (insn 59 58 60 4 (set (reg:SI 146)
> 	(if_then_else:SI (gt (reg:CC_NCV 24 cc)
>                 (const_int 0 [0]))
>             (reg:SI 145)
>             (reg:SI 144))) p.c:13 701 {*thumb2_movsicc_insn}
>      (nil))
> 
> which is wrong; the GT comparison requires testing of the Z, C, and V
> flags, which CC_NCV does not satisfy. The ICE happens later when the asm
> emitting actually hits assert fail in get_arm_condition_code().
> 
> This patch fixes this by stratifying the "arm_comparison_operator"
> predicate, by leveraging the current logic in get_arm_condition_code().
> I abstracted out the body into a new arm_comparison_to_cond_code()
> function, which returns an invalid code instead of assert fail, and used
> it to add a check to the comparison RTX in "arm_comparison_operator".
> This way, invalid comparisons like the above would be blocked from emitting.
> 
> Tests were run with no regressions found. Okay for trunk?
> 
> Thanks,
> Chung-Lin
> 
> 2011-01-12  Chung-Lin Tang  <cltang@codesourcery.com>
> 
>         * config/arm/arm.h (enum arm_cond_code): Add ARM_COND_INVALID.
>         * config/arm/arm.c (arm_comparison_to_cond_code): Renamed from
>         get_arm_condition_code(), change gcc_unreachable()s to return
>         ARM_COND_INVALID.
>         (get_arm_condition_code): Implement by calling
>         arm_comparison_to_cond_code(), with result test by gcc_assert().
>         (arm_valid_comparison_p): New function to test for valid ARM
>         comparison RTX.
>         * config/arm/arm-protos.h (arm_valid_comparison_p): Add
> 	prototype.
>         * config/arm/predicates.md (arm_comparison_operator): Add
> 	additional check based on arm_valid_comparison_p().
> 
>         testsuite/
>         * gcc.target/arm/20110112-1.c: New test.
> 
> 
>