The recent subreg-CSE allows a part of PR42587 to be fixed with
minimal surgery to the bswap pass - namely adding support for
BIT_FIELD_REF.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2016-05-13 Richard Biener <rguent...@suse.de>
PR tree-optimization/42587
* tree-ssa-math-opts.c (perform_symbolic_merge): Handle BIT_FIELD_REF.
(find_bswap_or_nop_1): Likewise.
(bswap_replace): Likewise.
* gcc.dg/optimize-bswapsi-4.c: New testcase.
Index: gcc/tree-ssa-math-opts.c
===================================================================
*** gcc/tree-ssa-math-opts.c (revision 236159)
--- gcc/tree-ssa-math-opts.c (working copy)
*************** perform_symbolic_merge (gimple *source_s
*** 2160,2168 ****
gimple *source_stmt;
struct symbolic_number *n_start;
/* Sources are different, cancel bswap if they are not memory location with
the same base (array, structure, ...). */
! if (gimple_assign_rhs1 (source_stmt1) != gimple_assign_rhs1 (source_stmt2))
{
uint64_t inc;
HOST_WIDE_INT start_sub, end_sub, end1, end2, end;
--- 2160,2175 ----
gimple *source_stmt;
struct symbolic_number *n_start;
+ tree rhs1 = gimple_assign_rhs1 (source_stmt1);
+ if (TREE_CODE (rhs1) == BIT_FIELD_REF)
+ rhs1 = TREE_OPERAND (rhs1, 0);
+ tree rhs2 = gimple_assign_rhs1 (source_stmt2);
+ if (TREE_CODE (rhs2) == BIT_FIELD_REF)
+ rhs2 = TREE_OPERAND (rhs2, 0);
+
/* Sources are different, cancel bswap if they are not memory location with
the same base (array, structure, ...). */
! if (rhs1 != rhs2)
{
uint64_t inc;
HOST_WIDE_INT start_sub, end_sub, end1, end2, end;
*************** find_bswap_or_nop_1 (gimple *stmt, struc
*** 2285,2290 ****
--- 2292,2330 ----
if (find_bswap_or_nop_load (stmt, rhs1, n))
return stmt;
+ /* Handle BIT_FIELD_REF. */
+ if (TREE_CODE (rhs1) == BIT_FIELD_REF
+ && TREE_CODE (TREE_OPERAND (rhs1, 0)) == SSA_NAME)
+ {
+ unsigned HOST_WIDE_INT bitsize = tree_to_uhwi (TREE_OPERAND (rhs1, 1));
+ unsigned HOST_WIDE_INT bitpos = tree_to_uhwi (TREE_OPERAND (rhs1, 2));
+ if (bitpos % BITS_PER_UNIT == 0
+ && bitsize % BITS_PER_UNIT == 0
+ && init_symbolic_number (n, TREE_OPERAND (rhs1, 0)))
+ {
+ /* Shift. */
+ if (!do_shift_rotate (RSHIFT_EXPR, n, bitpos))
+ return NULL;
+
+ /* Mask. */
+ uint64_t mask = 0;
+ uint64_t tmp = (1 << BITS_PER_UNIT) - 1;
+ for (unsigned i = 0; i < bitsize / BITS_PER_UNIT;
+ i++, tmp <<= BITS_PER_UNIT)
+ mask |= (uint64_t) MARKER_MASK << (i * BITS_PER_MARKER);
+ n->n &= mask;
+
+ /* Convert. */
+ n->type = TREE_TYPE (rhs1);
+ if (!n->base_addr)
+ n->range = TYPE_PRECISION (n->type) / BITS_PER_UNIT;
+
+ return verify_symbolic_number_p (n, stmt) ? stmt : NULL;
+ }
+
+ return NULL;
+ }
+
if (TREE_CODE (rhs1) != SSA_NAME)
return NULL;
*************** bswap_replace (gimple *cur_stmt, gimple
*** 2683,2688 ****
--- 2723,2730 ----
}
src = val_tmp;
}
+ else if (TREE_CODE (src) == BIT_FIELD_REF)
+ src = TREE_OPERAND (src, 0);
if (n->range == 16)
bswap_stats.found_16bit++;
Index: gcc/testsuite/gcc.dg/optimize-bswapsi-4.c
===================================================================
*** gcc/testsuite/gcc.dg/optimize-bswapsi-4.c (revision 0)
--- gcc/testsuite/gcc.dg/optimize-bswapsi-4.c (working copy)
***************
*** 0 ****
--- 1,28 ----
+ /* { dg-do compile } */
+ /* { dg-require-effective-target bswap32 } */
+ /* { dg-options "-O2 -fdump-tree-bswap" } */
+ /* { dg-additional-options "-march=z900" { target s390-*-* } } */
+
+ typedef unsigned char u8;
+ typedef unsigned int u32;
+ union __anonunion
+ {
+ u32 value;
+ u8 bytes[4];
+ };
+
+ u32
+ acpi_ut_dword_byte_swap (u32 value)
+ {
+ union __anonunion in;
+ in.value = value;
+ #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ return ((in.bytes[0] << 24) | (in.bytes[1] << 16)
+ | (in.bytes[2] << 8) | in.bytes[3]);
+ #else
+ return ((in.bytes[3] << 24) | (in.bytes[2] << 16)
+ | (in.bytes[1] << 8) | in.bytes[0]);
+ #endif
+ }
+
+ /* { dg-final { scan-tree-dump "32 bit bswap implementation found at" "bswap"
} } */
