On Tue, Oct 18, 2011 at 4:14 PM, William J. Schmidt
<wschm...@linux.vnet.ibm.com> wrote:
> Greetings,
>
> Here is a new revision of the tree portions of this patch. I moved the
> pattern recognizer to expand, and added additional logic to look for the
> same pattern in gimple form. I added two more tests to verify the new
> logic.
>
> I didn't run into any problems with the RTL CSE phases. I can't recall
> for certain what caused me to abandon the expand version previously.
> There may not have been good reason; too many versions to keep track of
> and too many interruptions, I suppose. In any case, I'm much happier
> having this code in the expander.
>
> Paolo's RTL logic for unpropagating the zero-offset case is not going to
> work out as is. It causes a number of performance degradations, which I
> suspect are due to the pass reordering. That's a separate issue,
> though, and not needed for this patch.
>
> Bootstrapped and regression-tested on powerpc64-linux. SPEC cpu2000
> shows a number of small improvements and no significant degradations.
> SPEC cpu2006 testing is pending.
>
> Thanks,
> Bill
>
>
> 2011-10-18 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>
> gcc:
>
> PR rtl-optimization/46556
> * expr.c (tree-pretty-print.h): New include.
> (restructure_base_and_offset): New function.
> (restructure_mem_ref): New function.
> (expand_expr_real_1): In MEM_REF case, attempt restructure_mem_ref
> first. In normal_inner_ref case, attempt restructure_base_and_offset
> first.
> * Makefile.in: Update dependences for expr.o.
>
> gcc/testsuite:
>
> PR rtl-optimization/46556
> * gcc.dg/tree-ssa-pr46556-1.c: New test.
> * gcc.dg/tree-ssa-pr46556-2.c: Likewise.
> * gcc.dg/tree-ssa-pr46556-3.c: Likewise.
> * gcc.dg/tree-ssa-pr46556-4.c: Likewise.
> * gcc.dg/tree-ssa-pr46556-5.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/testsuite/gcc.dg/tree-ssa/pr46556-4.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/pr46556-4.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr46556-4.c (revision 0)
> @@ -0,0 +1,28 @@
> +/* { 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 (*((int *)p + n*4), *((int *)p + 32 + n*4), *((int *)p + 16 + n*4));
> + if (n > 3)
> + {
> + foo (*((int *)p + n*4), *((int *)p + 32 + n*4), *((int *)p + 16 +
> n*4));
> + if (n > 12)
> + foo (*((int *)p + 16 + n*4), *((int *)p + n*4), *((int *)p + 32 +
> n*4));
> + }
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\(mem: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/pr46556-5.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/pr46556-5.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr46556-5.c (revision 0)
> @@ -0,0 +1,36 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-expand" } */
> +/* { dg-skip-if "" { lp64 } { "*" } { "-m32" } } */
> +/* { dg-skip-if "" { llp64 } { "*" } { "-m32" } } */
> +
> +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 (*((int *)p + n * 4),
> + *((int *)p + (n + 8) * 4),
> + *((int *)p + (n + 4) * 4));
> + if (n > 3)
> + {
> + foo (*((int *)p + n * 4),
> + *((int *)p + (n + 8) * 4),
> + *((int *)p + (n + 4) * 4));
> + if (n > 12)
> + foo (*((int *)p + (n + 4) * 4),
> + *((int *)p + n * 4),
> + *((int *)p + (n + 8) * 4));
> + }
> +}
> +
> +/* { dg-final { scan-rtl-dump-times "\\(mem: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 180138)
> +++ 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 +7649,157 @@ 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;
> +}
> +
> +/* Look for a hidden array reference in memory reference EXP. If found,
> + return a revised memory reference that restructures addressability
> + to combine constants. */
> +/* 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_mem_ref (tree exp)
> +{
> + tree s2, s3, t1, t2, offset_type, mult_expr, add_expr;
> + tree s2_op0, s2_op1, s3_op0, s3_op1, result;
> + gimple s1_stmt, s2_stmt, s3_stmt;
> + double_int c1, c2, c3, c;
> +
> + /* Currently we look for the following pattern, where each Si is an
> + SSA name, each Tj is an arbitrary tree, and each Ck is an integer
> + constant:
> +
> + S3 = T2 + C2;
> + S2 = S3 * C3;
> + S1 = T1 ptr+ S2;
> + exp = MEM_REF (S1, C1);
> +
> + This is rewritten as:
> +
> + exp = MEM_REF (T1 ptr+ (T2 * C3)), C1 + C2 * C3);
> +
> + */
> + if (TREE_CODE (TREE_OPERAND (exp, 0)) != SSA_NAME)
> + return NULL_TREE;
> +
> + /* We don't use get_def_for_expr for S1 because TER doesn't forward
> + S1 in some situations where this transform is useful, such as
> + when S1 is the base of two MEM_REFs fitting the pattern. */
> + s1_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (exp, 0));
You can't do this - this will possibly generate wrong code. You _do_
have to use get_def_for_expr. Or do it when we are still in "true" SSA form...
Richard.
> + if (!s1_stmt
> + || !is_gimple_assign (s1_stmt)
> + || gimple_assign_rhs_code (s1_stmt) != POINTER_PLUS_EXPR)
> + return NULL_TREE;
> +
> + c1 = mem_ref_offset (exp);
> + t1 = gimple_assign_rhs1 (s1_stmt);
> + s2 = gimple_assign_rhs2 (s1_stmt);
> +
> + if (TREE_CODE (s2) != SSA_NAME)
> + return NULL_TREE;
> +
> + s2_stmt = get_def_for_expr (s2, MULT_EXPR);
> +
> + if (!s2_stmt)
> + return NULL_TREE;
> +
> + s2_op0 = gimple_assign_rhs1 (s2_stmt);
> + s2_op1 = gimple_assign_rhs2 (s2_stmt);
> +
> + if (TREE_CODE (s2_op1) != INTEGER_CST)
> + return NULL_TREE;
> +
> + s3 = s2_op0;
> + c3 = tree_to_double_int (s2_op1);
> + s3_stmt = get_def_for_expr (s3, PLUS_EXPR);
> +
> + if (!s3_stmt)
> + return NULL_TREE;
> +
> + s3_op0 = gimple_assign_rhs1 (s3_stmt);
> + s3_op1 = gimple_assign_rhs2 (s3_stmt);
> +
> + if (TREE_CODE (s3_op1) != INTEGER_CST)
> + return NULL_TREE;
> +
> + t2 = s3_op0;
> + c2 = tree_to_double_int (s3_op1);
> + c = double_int_add (c1, double_int_mul (c2, c3));
> +
> + offset_type = TREE_TYPE (TREE_OPERAND (exp, 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);
> +
> + result = build2 (MEM_REF, TREE_TYPE (exp), add_expr,
> + double_int_to_tree (offset_type, c));
> +
> + return result;
> +}
> +
> +
> /* 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.
> @@ -9313,6 +9464,28 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
> gimple def_stmt;
> enum insn_code icode;
> unsigned align;
> + tree tem;
> +
> + /* Attempt to restructure a hidden array reference, such
> + as *(p + (n + k) * s). This generates dead code, so
> + require -O2. */
> + if (optimize > 1
> + && mode != BLKmode
> + && ((tem = restructure_mem_ref (exp)) != NULL_TREE))
> + {
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "\nRestructured memory 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);
> + }
> + copy_ref_info (tem, exp);
> + exp = tem;
> + base = TREE_OPERAND (exp, 0);
> + }
> +
> /* Handle expansion of non-aliased memory with non-BLKmode. That
> might end up in a register. */
> if (TREE_CODE (base) == ADDR_EXPR)
> @@ -9584,7 +9757,7 @@ 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 +9774,36 @@ 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 180138)
> +++ 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
>
>
>
