Date: Mon, 13 Apr 1998 11:52:42 +1000 (EST) From: Peter Jeremy <Peter.Jeremy@alcatel.com.au> To: bug-gcc@prep.ai.mit.edu Cc: freebsd-ports@FreeBSD.ORG Subject: gcc2.8.1 divide-by-constant optimisation causes call to __cmpdi2 Message-ID: <199804130152.LAA00492@gsms01.alcatel.com.au>
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gcc version 2.8.1 for i386-unknown-freebsd2.2.5 and sparc-sun-solaris2.5
Sample input file (testcase.i):
---
int test_int_ll(long long val)
{
return (val / 256);
}
---
Compile in the gcc build directory using:
./cc1 testcase.i -g
The problem is not affected by the use of -O2.
Compiler was configured on a FreeBSD 2.2.5R system using `./configure'
using the standard gcc 2.8.0 + 2.8.0->2.8.1 patches.
Compiler was configured on a Solaris 2.5.1 system in a subdirectory
of gcc-2.8.1 using
`../configure --with-gnu-ld --with-gnu-as --build=sparc-sun-solaris2.5'.
The compiler recognizes the use of a power-of-2 constant as the
denominator in the above division and expands it inline to a shift.
This requires special handling for negative numerators and so the
expanded code includes a comparison. In the case of long long
division, the comparison is not explicitly open-coded (unlike the
relational comparison expansions).
The problem is fixed for FreeBSD using the following patch. This patch
has not been tested on Solaris 2.x:
--
*** ChangeLog~ Sat Mar 28 08:03:41 1998
--- ChangeLog Sat Apr 11 09:09:50 1998
***************
*** 1,3 ****
--- 1,14 ----
+ Sat Apr 11 08:56:35 1998 Peter Jeremy <peter.jeremy@alcatel.com.au>
+
+ * expr.c (do_jump_by_parts_equality_rtx): Make function public
+ so it can be referenced from expmed.c.
+
+ * expmed.c (do_cmp_and_jump): New function based on multi-word
+ comparison handling in expr.c:do_jump().
+
+ * expmed.c (expand_divmod): convert emit_cmp_insn/emit_jump_insn
+ sequences to do_cmp_and_jump so multi-word modes are in-lined.
+
Mon Mar 2 08:06:58 1998 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* Version 2.8.1 released.
*** expmed.c~ Sun Nov 9 09:11:58 1997
--- expmed.c Sat Apr 11 09:15:53 1998
*************** static rtx mask_rtx PROTO((enum machin
*** 41,46 ****
--- 41,48 ----
static rtx lshift_value PROTO((enum machine_mode, rtx,
int, int));
static rtx extract_split_bit_field PROTO((rtx, int, int, int, int));
+ static void do_cmp_and_jump PROTO((rtx, rtx, enum rtx_code,
+ enum machine_mode, rtx));
#define CEIL(x,y) (((x) + (y) - 1) / (y))
*************** expand_divmod (rem_flag, code, mode, op0
*** 3027,3035 ****
rtx t1;
t1 = copy_to_mode_reg (compute_mode, op0);
! emit_cmp_insn (t1, const0_rtx, GE,
! NULL_RTX, compute_mode, 0, 0);
! emit_jump_insn (gen_bge (label));
expand_inc (t1, GEN_INT (abs_d - 1));
emit_label (label);
quotient = expand_shift (RSHIFT_EXPR, compute_mode, t1,
--- 3029,3036 ----
rtx t1;
t1 = copy_to_mode_reg (compute_mode, op0);
! do_cmp_and_jump (t1, const0_rtx, GE, compute_mode,
! label);
expand_inc (t1, GEN_INT (abs_d - 1));
emit_label (label);
quotient = expand_shift (RSHIFT_EXPR, compute_mode, t1,
*************** expand_divmod (rem_flag, code, mode, op0
*** 3255,3267 ****
Save that for later. */
rtx tem;
rtx label = gen_label_rtx ();
! emit_cmp_insn (remainder, const0_rtx, EQ, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_beq (label));
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
! emit_cmp_insn (tem, const0_rtx, GE, NULL_RTX, compute_mode, 0, 0);
! emit_jump_insn (gen_bge (label));
expand_dec (quotient, const1_rtx);
expand_inc (remainder, op1);
emit_label (label);
--- 3256,3265 ----
Save that for later. */
rtx tem;
rtx label = gen_label_rtx ();
! do_cmp_and_jump (remainder, const0_rtx, EQ, compute_mode, label);
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
! do_cmp_and_jump (tem, const0_rtx, GE, compute_mode, label);
expand_dec (quotient, const1_rtx);
expand_inc (remainder, op1);
emit_label (label);
*************** expand_divmod (rem_flag, code, mode, op0
*** 3282,3292 ****
label3 = gen_label_rtx ();
label4 = gen_label_rtx ();
label5 = gen_label_rtx ();
! emit_cmp_insn (op1, const0_rtx, LT, NULL_RTX, compute_mode, 0, 0);
emit_jump_insn (gen_blt (label2));
! emit_cmp_insn (adjusted_op0, const0_rtx, LT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_blt (label1));
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
--- 3280,3288 ----
label3 = gen_label_rtx ();
label4 = gen_label_rtx ();
label5 = gen_label_rtx ();
! do_cmp_and_jump (op1, const0_rtx, LT, compute_mode, label2);
emit_jump_insn (gen_blt (label2));
! do_cmp_and_jump (adjusted_op0, const0_rtx, LT, compute_mode, label1);
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
*************** expand_divmod (rem_flag, code, mode, op0
*** 3298,3306 ****
emit_jump_insn (gen_jump (label4));
emit_barrier ();
emit_label (label2);
! emit_cmp_insn (adjusted_op0, const0_rtx, GT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_bgt (label3));
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
--- 3294,3300 ----
emit_jump_insn (gen_jump (label4));
emit_barrier ();
emit_label (label2);
! do_cmp_and_jump (adjusted_op0, const0_rtx, GT, compute_mode, label3);
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
*************** expand_divmod (rem_flag, code, mode, op0
*** 3340,3348 ****
{
rtx lab;
lab = gen_label_rtx ();
! emit_cmp_insn (t2, const0_rtx, EQ, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_beq (lab));
expand_inc (t1, const1_rtx);
emit_label (lab);
quotient = t1;
--- 3334,3340 ----
{
rtx lab;
lab = gen_label_rtx ();
! do_cmp_and_jump (t2, const0_rtx, EQ, compute_mode, lab);
expand_inc (t1, const1_rtx);
emit_label (lab);
quotient = t1;
*************** expand_divmod (rem_flag, code, mode, op0
*** 3381,3389 ****
/* This could be computed with a branch-less sequence.
Save that for later. */
rtx label = gen_label_rtx ();
! emit_cmp_insn (remainder, const0_rtx, EQ, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_beq (label));
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
--- 3373,3380 ----
/* This could be computed with a branch-less sequence.
Save that for later. */
rtx label = gen_label_rtx ();
! do_cmp_and_jump (remainder, const0_rtx, EQ, compute_mode,
! label);
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
*************** expand_divmod (rem_flag, code, mode, op0
*** 3400,3408 ****
adjusted_op0 = copy_to_mode_reg (compute_mode, op0);
label1 = gen_label_rtx ();
label2 = gen_label_rtx ();
! emit_cmp_insn (adjusted_op0, const0_rtx, NE, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_bne (label1));
emit_move_insn (quotient, const0_rtx);
emit_jump_insn (gen_jump (label2));
emit_barrier ();
--- 3391,3398 ----
adjusted_op0 = copy_to_mode_reg (compute_mode, op0);
label1 = gen_label_rtx ();
label2 = gen_label_rtx ();
! do_cmp_and_jump (adjusted_op0, const0_rtx, NE, compute_mode,
! label1);
emit_move_insn (quotient, const0_rtx);
emit_jump_insn (gen_jump (label2));
emit_barrier ();
*************** expand_divmod (rem_flag, code, mode, op0
*** 3442,3450 ****
{
rtx lab;
lab = gen_label_rtx ();
! emit_cmp_insn (t2, const0_rtx, EQ, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_beq (lab));
expand_inc (t1, const1_rtx);
emit_label (lab);
quotient = t1;
--- 3432,3438 ----
{
rtx lab;
lab = gen_label_rtx ();
! do_cmp_and_jump (t2, const0_rtx, EQ, compute_mode, lab);
expand_inc (t1, const1_rtx);
emit_label (lab);
quotient = t1;
*************** expand_divmod (rem_flag, code, mode, op0
*** 3483,3496 ****
Save that for later. */
rtx tem;
rtx label = gen_label_rtx ();
! emit_cmp_insn (remainder, const0_rtx, EQ, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_beq (label));
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
! emit_cmp_insn (tem, const0_rtx, LT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_blt (label));
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
--- 3471,3481 ----
Save that for later. */
rtx tem;
rtx label = gen_label_rtx ();
! do_cmp_and_jump (remainder, const0_rtx, EQ, compute_mode,
! label);
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
! do_cmp_and_jump (tem, const0_rtx, LT, compute_mode, label);
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
*************** expand_divmod (rem_flag, code, mode, op0
*** 3511,3522 ****
label3 = gen_label_rtx ();
label4 = gen_label_rtx ();
label5 = gen_label_rtx ();
! emit_cmp_insn (op1, const0_rtx, LT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_blt (label2));
! emit_cmp_insn (adjusted_op0, const0_rtx, GT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_bgt (label1));
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
--- 3496,3504 ----
label3 = gen_label_rtx ();
label4 = gen_label_rtx ();
label5 = gen_label_rtx ();
! do_cmp_and_jump (op1, const0_rtx, LT, compute_mode, label2);
! do_cmp_and_jump (adjusted_op0, const0_rtx, GT, compute_mode,
! label1);
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
*************** expand_divmod (rem_flag, code, mode, op0
*** 3528,3536 ****
emit_jump_insn (gen_jump (label4));
emit_barrier ();
emit_label (label2);
! emit_cmp_insn (adjusted_op0, const0_rtx, LT, NULL_RTX,
! compute_mode, 0, 0);
! emit_jump_insn (gen_blt (label3));
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
--- 3510,3517 ----
emit_jump_insn (gen_jump (label4));
emit_barrier ();
emit_label (label2);
! do_cmp_and_jump (adjusted_op0, const0_rtx, LT, compute_mode,
! label3);
tem = expand_binop (compute_mode, sdiv_optab, adjusted_op0, op1,
quotient, 0, OPTAB_LIB_WIDEN);
if (tem != quotient)
*************** expand_divmod (rem_flag, code, mode, op0
*** 3596,3603 ****
tem = plus_constant (op1, -1);
tem = expand_shift (RSHIFT_EXPR, compute_mode, tem,
build_int_2 (1, 0), NULL_RTX, 1);
! emit_cmp_insn (remainder, tem, LEU, NULL_RTX, compute_mode, 0, 0);
! emit_jump_insn (gen_bleu (label));
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
--- 3577,3583 ----
tem = plus_constant (op1, -1);
tem = expand_shift (RSHIFT_EXPR, compute_mode, tem,
build_int_2 (1, 0), NULL_RTX, 1);
! do_cmp_and_jump (remainder, tem, LEU, compute_mode, label);
expand_inc (quotient, const1_rtx);
expand_dec (remainder, op1);
emit_label (label);
*************** expand_divmod (rem_flag, code, mode, op0
*** 3622,3629 ****
abs_op1 = expand_abs (compute_mode, op1, NULL_RTX, 0, 0);
tem = expand_shift (LSHIFT_EXPR, compute_mode, abs_rem,
build_int_2 (1, 0), NULL_RTX, 1);
! emit_cmp_insn (tem, abs_op1, LTU, NULL_RTX, compute_mode, 0, 0);
! emit_jump_insn (gen_bltu (label));
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
mask = expand_shift (RSHIFT_EXPR, compute_mode, tem,
--- 3602,3608 ----
abs_op1 = expand_abs (compute_mode, op1, NULL_RTX, 0, 0);
tem = expand_shift (LSHIFT_EXPR, compute_mode, abs_rem,
build_int_2 (1, 0), NULL_RTX, 1);
! do_cmp_and_jump (tem, abs_op1, LTU, compute_mode, label);
tem = expand_binop (compute_mode, xor_optab, op0, op1,
NULL_RTX, 0, OPTAB_WIDEN);
mask = expand_shift (RSHIFT_EXPR, compute_mode, tem,
*************** emit_store_flag_force (target, code, op0
*** 4327,4330 ****
--- 4306,4383 ----
emit_label (label);
return target;
+ }
+
+
+ /* Perform possibly multi-word comparison and conditional jump as follows:
+ * if (ARG1 OP ARG2) goto LABEL
+ * where ARG1 and ARG2 are of mode MODE
+ *
+ * The algorithm is based on the code in expr.c:do_jump().
+ *
+ * Note that this does not perform a general comparison. Only variants
+ * generated within expmed.c are correctly handled, others abort (but could
+ * be handled if needed).
+ */
+ static void
+ do_cmp_and_jump (arg1, arg2, op, mode, label)
+ rtx arg1, arg2, label;
+ enum rtx_code op;
+ enum machine_mode mode;
+ {
+ /* If this mode is an integer too wide to compare properly,
+ compare word by word. Rely on cse to optimize constant cases. */
+ if (GET_MODE_CLASS (mode) == MODE_INT && !can_compare_p (mode))
+ {
+ rtx label2 = gen_label_rtx ();
+
+ switch (op)
+ {
+ case LTU:
+ do_jump_by_parts_greater_rtx (mode, 1, arg2, arg1, label2, label);
+ break;
+
+ case LEU:
+ do_jump_by_parts_greater_rtx (mode, 1, arg1, arg2, label, label2);
+ break;
+
+ case LT:
+ do_jump_by_parts_greater_rtx (mode, 0, arg2, arg1, label2, label);
+ break;
+
+ case GT:
+ do_jump_by_parts_greater_rtx (mode, 0, arg1, arg2, label2, label);
+ break;
+
+ case GE:
+ do_jump_by_parts_greater_rtx (mode, 0, arg2, arg1, label, label2);
+ break;
+
+ /* do_jump_by_parts_equality_rtx() compares with zero. Luckily
+ * that's the only equality operations we do */
+ case EQ:
+ if (arg2 != const0_rtx || mode != GET_MODE(arg1))
+ abort();
+ do_jump_by_parts_equality_rtx (arg1, label2, label);
+ break;
+
+ case NE:
+ if (arg2 != const0_rtx || mode != GET_MODE(arg1))
+ abort();
+ do_jump_by_parts_equality_rtx (arg1, label, label2);
+ break;
+
+ default:
+ abort();
+ }
+
+ emit_label (label2);
+ }
+ else
+ {
+ emit_cmp_insn(arg1, arg2, op, NULL_RTX, mode, 0, 0);
+ if (bcc_gen_fctn[(int) op] == 0)
+ abort ();
+ emit_jump_insn ((*bcc_gen_fctn[(int) op]) (label));
+ }
}
*** expr.c~ Sat Mar 28 08:04:29 1998
--- expr.c Fri Apr 10 23:41:40 1998
*************** static void preexpand_calls PROTO((tree)
*** 209,215 ****
static void do_jump_by_parts_greater PROTO((tree, int, rtx, rtx));
void do_jump_by_parts_greater_rtx PROTO((enum machine_mode, int, rtx, rtx, rtx, rtx));
static void do_jump_by_parts_equality PROTO((tree, rtx, rtx));
! static void do_jump_by_parts_equality_rtx PROTO((rtx, rtx, rtx));
static void do_jump_for_compare PROTO((rtx, rtx, rtx));
static rtx compare PROTO((tree, enum rtx_code, enum rtx_code));
static rtx do_store_flag PROTO((tree, rtx, enum machine_mode, int));
--- 209,215 ----
static void do_jump_by_parts_greater PROTO((tree, int, rtx, rtx));
void do_jump_by_parts_greater_rtx PROTO((enum machine_mode, int, rtx, rtx, rtx, rtx));
static void do_jump_by_parts_equality PROTO((tree, rtx, rtx));
! void do_jump_by_parts_equality_rtx PROTO((rtx, rtx, rtx));
static void do_jump_for_compare PROTO((rtx, rtx, rtx));
static rtx compare PROTO((tree, enum rtx_code, enum rtx_code));
static rtx do_store_flag PROTO((tree, rtx, enum machine_mode, int));
*************** do_jump_by_parts_equality (exp, if_false
*** 10747,10753 ****
We assume that OP0 has an integer mode that is too wide
for the available compare insns. */
! static void
do_jump_by_parts_equality_rtx (op0, if_false_label, if_true_label)
rtx op0;
rtx if_false_label, if_true_label;
--- 10747,10753 ----
We assume that OP0 has an integer mode that is too wide
for the available compare insns. */
! void
do_jump_by_parts_equality_rtx (op0, if_false_label, if_true_label)
rtx op0;
rtx if_false_label, if_true_label;
---
Peter Jeremy (VK2PJ) peter.jeremy@alcatel.com.au
Alcatel Australia Limited
41 Mandible St Phone: +61 2 9690 5019
ALEXANDRIA NSW 2015 Fax: +61 2 9690 5247
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