| Message ID | HE1PR0801MB1482D3151EBD44465B472D46832D0@HE1PR0801MB1482.eurprd08.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Jun 23, 2016 at 6:34 PM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote: > This patch fixes a bug in the bswap pass. In big-endian BIT_FIELD_REF uses > big-endian bit numbering so we need to adjust the bit position. > The existing version could potentially generate incorrect code however GCC doesn't > emit a BIT_FIELD_REF to access the low byte in a register, so the symbolic number > never matches in big-endian. > > The test gcc.dg/optimize-bswapsi-4.c now passes on AArch64, no other changes. > OK for commit? Ok. Thanks, Richard. > ChangeLog: > 2016-06-23 Wilco Dijkstra <wdijkstr@arm.com> > > * gcc/tree-ssa-math-opts.c (find_bswap_or_nop_1): Adjust bitnumbering > for big-endian BIT_FIELD_REF. > > -- > diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c > index 513ef0b3f4eb29a35eae8a0eb14ee8f8c24fcfd9..d31c12fd818a713ca3d251b9464015b147235bbe 100644 > --- a/gcc/tree-ssa-math-opts.c > +++ b/gcc/tree-ssa-math-opts.c > @@ -2307,6 +2307,10 @@ find_bswap_or_nop_1 (gimple *stmt, struct symbolic_number *n, int limit) > && bitsize % BITS_PER_UNIT == 0 > && init_symbolic_number (n, TREE_OPERAND (rhs1, 0))) > { > + /* Handle big-endian bit numbering in BIT_FIELD_REF. */ > + if (BYTES_BIG_ENDIAN) > + bitpos = TYPE_PRECISION (n->type) - bitpos - bitsize; > + > /* Shift. */ > if (!do_shift_rotate (RSHIFT_EXPR, n, bitpos)) > return NULL; >
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c index 513ef0b3f4eb29a35eae8a0eb14ee8f8c24fcfd9..d31c12fd818a713ca3d251b9464015b147235bbe 100644 --- a/gcc/tree-ssa-math-opts.c +++ b/gcc/tree-ssa-math-opts.c @@ -2307,6 +2307,10 @@ find_bswap_or_nop_1 (gimple *stmt, struct symbolic_number *n, int limit) && bitsize % BITS_PER_UNIT == 0 && init_symbolic_number (n, TREE_OPERAND (rhs1, 0))) { + /* Handle big-endian bit numbering in BIT_FIELD_REF. */ + if (BYTES_BIG_ENDIAN) + bitpos = TYPE_PRECISION (n->type) - bitpos - bitsize; + /* Shift. */ if (!do_shift_rotate (RSHIFT_EXPR, n, bitpos)) return NULL;