> -----Original Message-----
> From: Richard Sandiford <richard.sandif...@arm.com>
> Sent: Friday, January 12, 2024 4:26 AM
> To: Andrew Pinski (QUIC) <quic_apin...@quicinc.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: [PATCHv3] aarch64/expr: Use ccmp when the outer expression is
> used twice [PR100942]
>
> Andrew Pinski <quic_apin...@quicinc.com> writes:
> > Ccmp is not used if the result of the and/ior is used by both
> > a GIMPLE_COND and a GIMPLE_ASSIGN. This improves the code generation
> > here by using ccmp in this case.
> > Two changes is required, first we need to allow the outer statement's
> > result be used more than once.
> > The second change is that during the expansion of the gimple, we need
> > to try using ccmp. This is needed because we don't use expand the ssa
> > name of the lhs but rather expand directly from the gimple.
> >
> > A small note on the ccmp_4.c testcase, we should be able to get slightly
> > better than with this patch but it is one extra instruction compared to
> > before.
> >
> > Diff from v1:
> > * v2: Split out expand_gimple_assign_ssa so the we only need to handle
> > promotion once. Add ccmp_5.c testcase which was suggested. Change
> comment
> > on ccmp_candidate_p.
>
> I meant more that we should split out the gassign handling in
> expand_expr_real_1, since we're effectively making cfgexpand follow
> it more closely. What do you think about the attached version?
> Tested on aarch64-linux-gnu and x86_64-linux-gnu.
>
> OK for the expr/cfgexpand bits?
Oh that is what I originally thought you wanted but I was not 100% sure so I
just
moved it out in one place. Anyways thanks for taking care of the change.
Thanks,
Andrew Pinski
>
> Thanks,
> Richard
>
> ----
>
> Ccmp is not used if the result of the and/ior is used by both
> a GIMPLE_COND and a GIMPLE_ASSIGN. This improves the code generation
> here by using ccmp in this case.
> Two changes is required, first we need to allow the outer statement's
> result be used more than once.
> The second change is that during the expansion of the gimple, we need
> to try using ccmp. This is needed because we don't use expand the ssa
> name of the lhs but rather expand directly from the gimple.
>
> A small note on the ccmp_4.c testcase, we should be able to get slightly
> better than with this patch but it is one extra instruction compared to
> before.
>
> PR target/100942
>
> gcc/ChangeLog:
>
> * ccmp.cc (ccmp_candidate_p): Add outer argument.
> Allow if the outer is true and the lhs is used more
> than once.
> (expand_ccmp_expr): Update call to ccmp_candidate_p.
> * expr.h (expand_expr_real_gassign): Declare.
> * expr.cc (expand_expr_real_gassign): New function, split out from...
> (expand_expr_real_1): ...here.
> * cfgexpand.cc (expand_gimple_stmt_1): Use
> expand_expr_real_gassign.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/aarch64/ccmp_3.c: New test.
> * gcc.target/aarch64/ccmp_4.c: New test.
> * gcc.target/aarch64/ccmp_5.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> Co-authored-by: Richard Sandiford <richard.sandif...@arm.com>
> ---
> gcc/ccmp.cc | 12 +--
> gcc/cfgexpand.cc | 31 ++-----
> gcc/expr.cc | 103 ++++++++++++----------
> gcc/expr.h | 3 +
> gcc/testsuite/gcc.target/aarch64/ccmp_3.c | 20 +++++
> gcc/testsuite/gcc.target/aarch64/ccmp_4.c | 35 ++++++++
> gcc/testsuite/gcc.target/aarch64/ccmp_5.c | 20 +++++
> 7 files changed, 149 insertions(+), 75 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/aarch64/ccmp_3.c
> create mode 100644 gcc/testsuite/gcc.target/aarch64/ccmp_4.c
> create mode 100644 gcc/testsuite/gcc.target/aarch64/ccmp_5.c
>
> diff --git a/gcc/ccmp.cc b/gcc/ccmp.cc
> index 09d6b5595a4..7cb525addf4 100644
> --- a/gcc/ccmp.cc
> +++ b/gcc/ccmp.cc
> @@ -90,9 +90,10 @@ ccmp_tree_comparison_p (tree t, basic_block bb)
> If all checks OK in expand_ccmp_expr, it emits insns in prep_seq, then
> insns in gen_seq. */
>
> -/* Check whether G is a potential conditional compare candidate. */
> +/* Check whether G is a potential conditional compare candidate; OUTER is
> true if
> + G is the outer most AND/IOR. */
> static bool
> -ccmp_candidate_p (gimple *g)
> +ccmp_candidate_p (gimple *g, bool outer = false)
> {
> tree lhs, op0, op1;
> gimple *gs0, *gs1;
> @@ -109,8 +110,9 @@ ccmp_candidate_p (gimple *g)
> lhs = gimple_assign_lhs (g);
> op0 = gimple_assign_rhs1 (g);
> op1 = gimple_assign_rhs2 (g);
> - if ((TREE_CODE (op0) != SSA_NAME) || (TREE_CODE (op1) != SSA_NAME)
> - || !has_single_use (lhs))
> + if ((TREE_CODE (op0) != SSA_NAME) || (TREE_CODE (op1) != SSA_NAME))
> + return false;
> + if (!outer && !has_single_use (lhs))
> return false;
>
> bb = gimple_bb (g);
> @@ -284,7 +286,7 @@ expand_ccmp_expr (gimple *g, machine_mode
> mode)
> rtx_insn *last;
> rtx tmp;
>
> - if (!ccmp_candidate_p (g))
> + if (!ccmp_candidate_p (g, true))
> return NULL_RTX;
>
> last = get_last_insn ();
> diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
> index 1db22f0a1a3..381ed2c82d7 100644
> --- a/gcc/cfgexpand.cc
> +++ b/gcc/cfgexpand.cc
> @@ -3971,37 +3971,18 @@ expand_gimple_stmt_1 (gimple *stmt)
> {
> rtx target, temp;
> bool nontemporal = gimple_assign_nontemporal_move_p
> (assign_stmt);
> - struct separate_ops ops;
> bool promoted = false;
>
> target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> if (GET_CODE (target) == SUBREG && SUBREG_PROMOTED_VAR_P
> (target))
> promoted = true;
>
> - ops.code = gimple_assign_rhs_code (assign_stmt);
> - ops.type = TREE_TYPE (lhs);
> - switch (get_gimple_rhs_class (ops.code))
> - {
> - case GIMPLE_TERNARY_RHS:
> - ops.op2 = gimple_assign_rhs3 (assign_stmt);
> - /* Fallthru */
> - case GIMPLE_BINARY_RHS:
> - ops.op1 = gimple_assign_rhs2 (assign_stmt);
> - /* Fallthru */
> - case GIMPLE_UNARY_RHS:
> - ops.op0 = gimple_assign_rhs1 (assign_stmt);
> - break;
> - default:
> - gcc_unreachable ();
> - }
> - ops.location = gimple_location (stmt);
> -
> - /* If we want to use a nontemporal store, force the value to
> - register first. If we store into a promoted register,
> - don't directly expand to target. */
> + /* If we want to use a nontemporal store, force the value to
> + register first. If we store into a promoted register,
> + don't directly expand to target. */
> temp = nontemporal || promoted ? NULL_RTX : target;
> - temp = expand_expr_real_2 (&ops, temp, GET_MODE (target),
> - EXPAND_NORMAL);
> + temp = expand_expr_real_gassign (assign_stmt, temp,
> + GET_MODE (target),
> EXPAND_NORMAL);
>
> if (temp == target)
> ;
> @@ -4013,7 +3994,7 @@ expand_gimple_stmt_1 (gimple *stmt)
> if (CONSTANT_P (temp) && GET_MODE (temp) == VOIDmode)
> {
> temp = convert_modes (GET_MODE (target),
> - TYPE_MODE (ops.type),
> + TYPE_MODE (TREE_TYPE (lhs)),
> temp, unsignedp);
> temp = convert_modes (GET_MODE (SUBREG_REG (target)),
> GET_MODE (target), temp,
> unsignedp);
> diff --git a/gcc/expr.cc b/gcc/expr.cc
> index dc816bc20fa..f9052a6ff5f 100644
> --- a/gcc/expr.cc
> +++ b/gcc/expr.cc
> @@ -11035,6 +11035,62 @@ stmt_is_replaceable_p (gimple *stmt)
> return false;
> }
>
> +/* A subroutine of expand_expr_real_1. Expand gimple assignment G,
> + which is known to set an SSA_NAME result. The other arguments are
> + as for expand_expr_real_1. */
> +
> +rtx
> +expand_expr_real_gassign (gassign *g, rtx target, machine_mode tmode,
> + enum expand_modifier modifier, rtx *alt_rtl,
> + bool inner_reference_p)
> +{
> + separate_ops ops;
> + rtx r;
> + location_t saved_loc = curr_insn_location ();
> + auto loc = gimple_location (g);
> + if (loc != UNKNOWN_LOCATION)
> + set_curr_insn_location (loc);
> + tree lhs = gimple_assign_lhs (g);
> + ops.code = gimple_assign_rhs_code (g);
> + ops.type = TREE_TYPE (lhs);
> + switch (get_gimple_rhs_class (ops.code))
> + {
> + case GIMPLE_TERNARY_RHS:
> + ops.op2 = gimple_assign_rhs3 (g);
> + /* Fallthru */
> + case GIMPLE_BINARY_RHS:
> + ops.op1 = gimple_assign_rhs2 (g);
> +
> + /* Try to expand conditonal compare. */
> + if (targetm.gen_ccmp_first)
> + {
> + gcc_checking_assert (targetm.gen_ccmp_next != NULL);
> + r = expand_ccmp_expr (g, TYPE_MODE (ops.type));
> + if (r)
> + break;
> + }
> + /* Fallthru */
> + case GIMPLE_UNARY_RHS:
> + ops.op0 = gimple_assign_rhs1 (g);
> + ops.location = loc;
> + r = expand_expr_real_2 (&ops, target, tmode, modifier);
> + break;
> + case GIMPLE_SINGLE_RHS:
> + {
> + r = expand_expr_real (gimple_assign_rhs1 (g), target,
> + tmode, modifier, alt_rtl,
> + inner_reference_p);
> + break;
> + }
> + default:
> + gcc_unreachable ();
> + }
> + set_curr_insn_location (saved_loc);
> + if (REG_P (r) && !REG_EXPR (r))
> + set_reg_attrs_for_decl_rtl (lhs, r);
> + return r;
> +}
> +
> rtx
> expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
> enum expand_modifier modifier, rtx *alt_rtl,
> @@ -11198,51 +11254,8 @@ expand_expr_real_1 (tree exp, rtx target,
> machine_mode tmode,
> && stmt_is_replaceable_p (SSA_NAME_DEF_STMT (exp)))
> g = SSA_NAME_DEF_STMT (exp);
> if (g)
> - {
> - rtx r;
> - location_t saved_loc = curr_insn_location ();
> - loc = gimple_location (g);
> - if (loc != UNKNOWN_LOCATION)
> - set_curr_insn_location (loc);
> - ops.code = gimple_assign_rhs_code (g);
> - switch (get_gimple_rhs_class (ops.code))
> - {
> - case GIMPLE_TERNARY_RHS:
> - ops.op2 = gimple_assign_rhs3 (g);
> - /* Fallthru */
> - case GIMPLE_BINARY_RHS:
> - ops.op1 = gimple_assign_rhs2 (g);
> -
> - /* Try to expand conditonal compare. */
> - if (targetm.gen_ccmp_first)
> - {
> - gcc_checking_assert (targetm.gen_ccmp_next != NULL);
> - r = expand_ccmp_expr (g, mode);
> - if (r)
> - break;
> - }
> - /* Fallthru */
> - case GIMPLE_UNARY_RHS:
> - ops.op0 = gimple_assign_rhs1 (g);
> - ops.type = TREE_TYPE (gimple_assign_lhs (g));
> - ops.location = loc;
> - r = expand_expr_real_2 (&ops, target, tmode, modifier);
> - break;
> - case GIMPLE_SINGLE_RHS:
> - {
> - r = expand_expr_real (gimple_assign_rhs1 (g), target,
> - tmode, modifier, alt_rtl,
> - inner_reference_p);
> - break;
> - }
> - default:
> - gcc_unreachable ();
> - }
> - set_curr_insn_location (saved_loc);
> - if (REG_P (r) && !REG_EXPR (r))
> - set_reg_attrs_for_decl_rtl (SSA_NAME_VAR (exp), r);
> - return r;
> - }
> + return expand_expr_real_gassign (as_a<gassign *> (g), target, tmode,
> + modifier, alt_rtl, inner_reference_p);
>
> ssa_name = exp;
> decl_rtl = get_rtx_for_ssa_name (ssa_name);
> diff --git a/gcc/expr.h b/gcc/expr.h
> index f04f40da6ab..64956f63029 100644
> --- a/gcc/expr.h
> +++ b/gcc/expr.h
> @@ -302,6 +302,9 @@ extern rtx expand_expr_real_1 (tree, rtx,
> machine_mode,
> enum expand_modifier, rtx *, bool);
> extern rtx expand_expr_real_2 (sepops, rtx, machine_mode,
> enum expand_modifier);
> +extern rtx expand_expr_real_gassign (gassign *, rtx, machine_mode,
> + enum expand_modifier modifier,
> + rtx * = nullptr, bool = false);
>
> /* Generate code for computing expression EXP.
> An rtx for the computed value is returned. The value is never null.
> diff --git a/gcc/testsuite/gcc.target/aarch64/ccmp_3.c
> b/gcc/testsuite/gcc.target/aarch64/ccmp_3.c
> new file mode 100644
> index 00000000000..a2b47fbee14
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/ccmp_3.c
> @@ -0,0 +1,20 @@
> +/* { dg-options "-O2" } */
> +/* PR target/100942 */
> +
> +void foo(void);
> +int f1(int a, int b)
> +{
> + int c = a == 0 || b == 0;
> + if (c) foo();
> + return c;
> +}
> +
> +/* We should get one cmp followed by ccmp and one cset. */
> +/* { dg-final { scan-assembler "\tccmp\t" } } */
> +/* { dg-final { scan-assembler-times "\tcset\t" 1 } } */
> +/* { dg-final { scan-assembler-times "\tcmp\t" 1 } } */
> +/* And not get 2 cmps and 2 (or more cset) and orr and a cbnz. */
> +/* { dg-final { scan-assembler-not "\torr\t" } } */
> +/* { dg-final { scan-assembler-not "\tcbnz\t" } } */
> +/* { dg-final { scan-assembler-not "\tcbz\t" } } */
> +
> diff --git a/gcc/testsuite/gcc.target/aarch64/ccmp_4.c
> b/gcc/testsuite/gcc.target/aarch64/ccmp_4.c
> new file mode 100644
> index 00000000000..bc0f57a7c59
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/ccmp_4.c
> @@ -0,0 +1,35 @@
> +/* { dg-options "-O2" } */
> +/* PR target/100942 */
> +
> +void foo(void);
> +int f1(int a, int b, int d)
> +{
> + int c = a < 8 || b < 9;
> + int e = d < 11 || c;
> + if (e) foo();
> + return c;
> +}
> +
> +/*
> + We really should get:
> + cmp w0, 7
> + ccmp w1, 8, 4, gt
> + cset w0, le
> + ccmp w2, 10, 4, gt
> + ble .L11
> +
> + But we currently get:
> + cmp w0, 7
> + ccmp w1, 8, 4, gt
> + cset w0, le
> + cmp w0, 0
> + ccmp w2, 10, 4, eq
> + ble .L11
> + The middle cmp is not needed.
> + */
> +
> +/* We should end up with only one cmp and 2 ccmp and 1 cset but currently
> we get 2 cmp
> + though. */
> +/* { dg-final { scan-assembler-times "\tccmp\t" 2 } } */
> +/* { dg-final { scan-assembler-times "\tcset\t" 1 } } */
> +/* { dg-final { scan-assembler-times "\tcmp\t" 1 { xfail *-*-* } } } */
> diff --git a/gcc/testsuite/gcc.target/aarch64/ccmp_5.c
> b/gcc/testsuite/gcc.target/aarch64/ccmp_5.c
> new file mode 100644
> index 00000000000..7e52ae4f322
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/ccmp_5.c
> @@ -0,0 +1,20 @@
> +
> +/* { dg-options "-O2" } */
> +/* PR target/100942 */
> +void f1(int a, int b, _Bool *x)
> +{
> + x[0] = x[1] = a == 0 || b == 0;
> +}
> +
> +void f2(int a, int b, int *x)
> +{
> + x[0] = x[1] = a == 0 || b == 0;
> +}
> +
> +
> +/* Both functions should be using ccmp rather than 2 cset/orr. */
> +/* { dg-final { scan-assembler-times "\tccmp\t" 2 } } */
> +/* { dg-final { scan-assembler-times "\tcset\t" 2 } } */
> +/* { dg-final { scan-assembler-times "\tcmp\t" 2 } } */
> +/* { dg-final { scan-assembler-not "\torr\t" } } */
> +
> --
> 2.25.1
