[ARM][PATCH] Add support for overflow add, sub, and neg operations

[Michael Collison]

Hi,

This patch improves code generations for builtin arithmetic overflow operations 
for the arm backend. As an example for a simple test case such as:

int
fn3 (int x, int y, int *ovf)
{
  int res;
  *ovf = __builtin_sadd_overflow (x, y, &res);
  return res;
}

Current trunk at -O2 generates

fn3:
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        @ link register save eliminated.
        cmp     r1, #0
        mov     r3, #0
        add     r1, r0, r1
        blt     .L4
        cmp     r1, r0
        blt     .L3
.L2:
        str     r3, [r2]
        mov     r0, r1
        bx      lr
.L4:
        cmp     r1, r0
        ble     .L2
.L3:
        mov     r3, #1
        b       .L2

With the patch this now generates:

       adds    r0, r0, r1
       movvs   r3, #1
       movvc   r3, #0
       str     r3, [r2]
       bx      lr

Ok for trunk?

2016-07-27  Michael Collison <michael.colli...@linaro.org>
         Michael Collison <michael.colli...@arm.com>

     * config/arm/arm-modes.def: Add new condition code mode CC_V
     to represent the overflow bit.
     * config/arm/arm.c (maybe_get_arm_condition_code):
     Add support for CC_Vmode.
     (arm_gen_unlikely_cbranch): New function to generate common
     rtl conditional branches for overflow patterns.
     * config/arm/arm-protos.h: Add prototype for
     arm_gen_unlikely_cbranch.
     * config/arm/arm.md (addv<mode>4, add<mode>3_compareV,
     addsi3_compareV_upper): New patterns to support signed
     builtin overflow add operations.
     (uaddv<mode>4, add<mode>3_compareC, addsi3_compareV_upper):
     New patterns to support unsigned builtin add overflow operations.
     (subv<mode>4, sub<mode>3_compare1): New patterns to support signed
     builtin overflow subtract operations,
     (usubv<mode>4): New patterns to support unsigned builtin subtract
     overflow operations.
     (negvsi3, negvdi3, negdi2_compare, negsi2_carryin_compare): New patterns
     to support builtin overflow negate operations.
     * gcc.target/arm/builtin_saddl.c: New testcase.
     * gcc.target/arm/builtin_saddll.c: New testcase.
     * gcc.target/arm/builtin_uaddl.c: New testcase.
     * gcc.target/arm/builtin_uaddll.c: New testcase.
     * gcc.target/arm/builtin_ssubl.c: New testcase.
     * gcc.target/arm/builtin_ssubll.c: New testcase.
     * gcc.target/arm/builtin_usubl.c: New testcase.
     * gcc.target/arm/builtin_usubll.c: New testcase.

bugzilla-69663-upstream-final.patch
Description: bugzilla-69663-upstream-final.patch