Ping.
On Mon, 2011-10-24 at 08:38 -0500, William J. Schmidt wrote:
> OK, I've removed the pointer-arithmetic case from expand, to be handled
> later by straight-line strength reduction. Here's the patch to deal
> with just the specific pattern of PR46556 (which will also eventually be
> handled by strength reduction, but not as quickly).
>
> (FYI, I've been thinking through the strength reduction pass, and my
> plan is to stage in some of the easiest cases first, hopefully for 4.7,
> and gradually add the more complex pieces. Explicit multiplies in the
> IL with known constants can be done pretty easily. More complexity is
> added when the multiplier is a variable, when conditional increments are
> present, and when multiplies are hidden in addressing expressions.)
>
> The present patch was bootstrapped and regression-tested on
> powerpc64-linux. OK for trunk?
>
> Thanks,
> Bill
>
>
> 2011-10-24 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>
> gcc:
>
> PR rtl-optimization/46556
> * expr.c (restructure_base_and_offset): New function.
> (expand_expr_real_1): Replace result of get_inner_reference
> with result of restructure_base_and_offset when applicable.
> * Makefile.in (expr.o): Update dependencies.
>
> gcc/testsuite:
>
> PR rtl-optimization/46556
> * gcc.dg/tree-ssa-pr46556-1.c: New testcase.
> * gcc.dg/tree-ssa-pr46556-2.c: Likewise.
> * gcc.dg/tree-ssa-pr46556-3.c: Likewise.
>
>
> Index: gcc/testsuite/gcc.dg/tree-ssa/pr46556-1.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/pr46556-1.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr46556-1.c (revision 0)
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-expand" } */
> +
> +struct x
> +{
> + int a[16];
> + int b[16];
> + int c[16];
> +};
> +
> +extern void foo (int, int, int);
> +
> +void
> +f (struct x *p, unsigned int n)
> +{
> + foo (p->a[n], p->c[n], p->b[n]);
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\(mem/s:SI \\(plus:" 2 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 128" 1 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 64 \\\[0x40\\\]\\)\\) \\\[" 1
> "expand" } } */
> +/* { dg-final { cleanup-rtl-dump "expand" } } */
> Index: gcc/testsuite/gcc.dg/tree-ssa/pr46556-2.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/pr46556-2.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr46556-2.c (revision 0)
> @@ -0,0 +1,26 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-expand" } */
> +
> +struct x
> +{
> + int a[16];
> + int b[16];
> + int c[16];
> +};
> +
> +extern void foo (int, int, int);
> +
> +void
> +f (struct x *p, unsigned int n)
> +{
> + foo (p->a[n], p->c[n], p->b[n]);
> + if (n > 12)
> + foo (p->a[n], p->c[n], p->b[n]);
> + else if (n > 3)
> + foo (p->b[n], p->a[n], p->c[n]);
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\(mem/s:SI \\(plus:" 6 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 128" 3 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 64 \\\[0x40\\\]\\)\\) \\\[" 3
> "expand" } } */
> +/* { dg-final { cleanup-rtl-dump "expand" } } */
> Index: gcc/testsuite/gcc.dg/tree-ssa/pr46556-3.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/pr46556-3.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr46556-3.c (revision 0)
> @@ -0,0 +1,27 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-expand" } */
> +struct x
> +{
> + int a[16];
> + int b[16];
> + int c[16];
> +};
> +
> +extern void foo (int, int, int);
> +
> +void
> +f (struct x *p, unsigned int n)
> +{
> + foo (p->a[n], p->c[n], p->b[n]);
> + if (n > 3)
> + {
> + foo (p->a[n], p->c[n], p->b[n]);
> + if (n > 12)
> + foo (p->b[n], p->a[n], p->c[n]);
> + }
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\(mem/s:SI \\(plus:" 6 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 128" 3 "expand" } } */
> +/* { dg-final { scan-rtl-dump-times "const_int 64 \\\[0x40\\\]\\)\\) \\\[" 3
> "expand" } } */
> +/* { dg-final { cleanup-rtl-dump "expand" } } */
> Index: gcc/expr.c
> ===================================================================
> --- gcc/expr.c (revision 180378)
> +++ gcc/expr.c (working copy)
> @@ -56,6 +56,7 @@ along with GCC; see the file COPYING3. If not see
> #include "ssaexpand.h"
> #include "target-globals.h"
> #include "params.h"
> +#include "tree-pretty-print.h"
>
> /* Decide whether a function's arguments should be processed
> from first to last or from last to first.
> @@ -7648,7 +7649,66 @@ expand_constructor (tree exp, rtx target, enum exp
> return target;
> }
>
> +/* Given BASE, OFFSET, and BITPOS derived from EXPR, determine whether
> + there is a profitable opportunity to restructure address arithmetic
> + within BASE and OFFSET. If so, produce such a restructuring and
> + return it. */
> +/* TODO: This belongs more properly in a separate pass that performs
> + general strength reduction on straight-line code. Eventually move
> + this there. */
>
> +static tree
> +restructure_base_and_offset (tree expr, tree base, tree offset,
> + HOST_WIDE_INT bitpos)
> +{
> + tree mult_op0, mult_op1, t1, t2, offset_type, mult_expr, add_expr, mem_ref;
> + double_int c, c1, c2, c3, c4;
> +
> + /* Look for the following pattern:
> +
> + base = MEM_REF (T1, C1);
> + offset = MULT_EXPR (PLUS_EXPR (T2, C2), C3)
> + bitpos = C4 * BITS_PER_UNIT
> +
> + If found, convert it to:
> +
> + MEM_REF (POINTER_PLUS_EXPR (T1, MULT_EXPR (T2, C3)),
> + C1 + (C2 * C3) + C4)
> + */
> + if (!base
> + || !offset
> + || TREE_CODE (base) != MEM_REF
> + || TREE_CODE (offset) != MULT_EXPR)
> + return NULL_TREE;
> +
> + mult_op0 = TREE_OPERAND (offset, 0);
> + mult_op1 = TREE_OPERAND (offset, 1);
> +
> + if (TREE_CODE (mult_op0) != PLUS_EXPR
> + || TREE_CODE (mult_op1) != INTEGER_CST
> + || TREE_CODE (TREE_OPERAND (mult_op0, 1)) != INTEGER_CST)
> + return NULL_TREE;
> +
> + t1 = TREE_OPERAND (base, 0);
> + t2 = TREE_OPERAND (mult_op0, 0);
> + c1 = mem_ref_offset (base);
> + c2 = tree_to_double_int (TREE_OPERAND (mult_op0, 1));
> + c3 = tree_to_double_int (mult_op1);
> + c4 = uhwi_to_double_int (bitpos / BITS_PER_UNIT);
> + c = double_int_add (double_int_add (c1, double_int_mul (c2, c3)), c4);
> +
> + offset_type = TREE_TYPE (TREE_OPERAND (base, 1));
> +
> + mult_expr = fold_build2 (MULT_EXPR, sizetype, t2,
> + double_int_to_tree (sizetype, c3));
> +
> + add_expr = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (t1), t1, mult_expr);
> +
> + mem_ref = fold_build2 (MEM_REF, TREE_TYPE (expr), add_expr,
> + double_int_to_tree (offset_type, c));
> + return mem_ref;
> +}
> +
> /* expand_expr: generate code for computing expression EXP.
> An rtx for the computed value is returned. The value is never null.
> In the case of a void EXP, const0_rtx is returned.
> @@ -9584,7 +9644,7 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
> {
> enum machine_mode mode1, mode2;
> HOST_WIDE_INT bitsize, bitpos;
> - tree offset;
> + tree offset, tem2;
> int volatilep = 0, must_force_mem;
> bool packedp = false;
> tree tem = get_inner_reference (exp, &bitsize, &bitpos, &offset,
> @@ -9601,6 +9661,36 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
> && DECL_PACKED (TREE_OPERAND (exp, 1))))
> packedp = true;
>
> + /* Attempt to restructure the base and offset to combine constants.
> + Bitfield references should eventually be lowered prior to this
> + point and are not dealt with. Skip BLKmode aggregates as well.
> + This generates dead code, so require -O2. */
> + if (optimize > 1
> + && code != BIT_FIELD_REF
> + && (code != COMPONENT_REF
> + || !DECL_BIT_FIELD (TREE_OPERAND (exp, 1)))
> + && TYPE_MODE (TREE_TYPE (exp)) != BLKmode
> + && bitpos % BITS_PER_UNIT == 0
> + && ((tem2 = restructure_base_and_offset (exp, tem, offset, bitpos))
> + != NULL_TREE))
> + {
> + copy_ref_info (tem2, exp);
> + tem = tem2;
> + /* The offset and bitpos were absorbed into the new MEM_REF, so
> + make sure we don't add them in again. */
> + offset = NULL_TREE;
> + bitpos = 0;
> +
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "\nRestructured inner reference:\n");
> + fprintf (dump_file, " Original reference: ");
> + print_generic_expr (dump_file, exp, TDF_VOPS|TDF_MEMSYMS);
> + fprintf (dump_file, "\n Replacement: ");
> + print_generic_expr (dump_file, tem, TDF_VOPS|TDF_MEMSYMS);
> + }
> + }
> +
> /* If TEM's type is a union of variable size, pass TARGET to the inner
> computation, since it will need a temporary and TARGET is known
> to have to do. This occurs in unchecked conversion in Ada. */
> Index: gcc/Makefile.in
> ===================================================================
> --- gcc/Makefile.in (revision 180378)
> +++ gcc/Makefile.in (working copy)
> @@ -2926,7 +2926,7 @@ expr.o : expr.c $(CONFIG_H) $(SYSTEM_H) coretypes.
> reload.h langhooks.h intl.h $(TM_P_H) $(TARGET_H) \
> tree-iterator.h gt-expr.h $(MACHMODE_H) $(TIMEVAR_H) $(TREE_FLOW_H) \
> $(TREE_PASS_H) $(DF_H) $(DIAGNOSTIC_H) vecprim.h $(SSAEXPAND_H) \
> - $(PARAMS_H) $(COMMON_TARGET_H)
> + $(PARAMS_H) $(COMMON_TARGET_H) tree-pretty-print.h
> dojump.o : dojump.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H)
> $(TREE_H) \
> $(FLAGS_H) $(FUNCTION_H) $(EXPR_H) $(OPTABS_H) $(INSN_ATTR_H)
> insn-config.h \
> langhooks.h $(GGC_H) gt-dojump.h vecprim.h $(BASIC_BLOCK_H) output.h
>
>