[PATCH][Aarch64] Add support for overflow add and sub operations

[Michael Collison]

Hi,

This patch improves code generations for builtin arithmetic overflow operations 
for the aarch64 backend. As an example for a simple test case such as:

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

Current trunk at -O2 generates

f:
        mov     w3, w0
        mov     w4, 0
        add     w0, w0, w1
        tbnz    w1, #31, .L4
        cmp     w0, w3
        blt     .L3
.L2:
        str     w4, [x2]
        ret
        .p2align 3
.L4:
        cmp     w0, w3
        ble     .L2
.L3:
        mov     w4, 1
        b       .L2


With the patch this now generates:

f:
        adds    w0, w0, w1
        cset    w1, vs
        str     w1, [x2]
        ret

Tested on aarch64-linux-gnu with no regressions. Okay for trunk?


2016-11-30  Michael Collison  <michael.colli...@arm.com>
            Richard Henderson <r...@redhat.com>

        * config/aarch64/aarch64-modes.def (CC_V): New.
        * config/aarch64/aarch64.c (aarch64_select_cc_mode): Test
        for signed overflow using CC_Vmode.
        (aarch64_get_condition_code_1): Handle CC_Vmode.
        * config/aarch64/aarch64.md (addv<GPI>4, uaddv<GPI>4): New.
        (addti3): Create simpler code if low part is already known to be 0.
        (addvti4, uaddvti4): New.
        (*add<GPI>3_compareC_cconly_imm): New.
        (*add<GPI>3_compareC_cconly): New.
        (*add<GPI>3_compareC_imm): New.
        (*add<GPI>3_compareC): Rename from add<GPI>3_compare1; do not
        handle constants within this pattern.
        (*add<GPI>3_compareV_cconly_imm): New.
        (*add<GPI>3_compareV_cconly): New.
        (*add<GPI>3_compareV_imm): New.
        (add<GPI>3_compareV): New.
        (add<GPI>3_carryinC, add<GPI>3_carryinV): New.
        (*add<GPI>3_carryinC_zero, *add<GPI>3_carryinV_zero): New.
        (*add<GPI>3_carryinC, *add<GPI>3_carryinV): New.
        (subv<GPI>4, usubv<GPI>4): New.
        (subti): Handle op1 zero.
        (subvti4, usub4ti4): New.
        (*sub<GPI>3_compare1_imm): New.
        (sub<GPI>3_carryinCV): New.
        (*sub<GPI>3_carryinCV_z1_z2, *sub<GPI>3_carryinCV_z1): New.
        (*sub<GPI>3_carryinCV_z2, *sub<GPI>3_carryinCV): New

rth_overflow_ipreview1.patch
Description: rth_overflow_ipreview1.patch