From f6922a5660bc593d7eed186c0538eb28269fcbe5 Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Tue, 28 Jun 2016 13:57:47 +0000 Subject: [PATCH] This patch fixes a bug in the bswap pass. 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. gcc/ * tree-ssa-math-opts.c (find_bswap_or_nop_1): Adjust bitnumbering for big-endian BIT_FIELD_REF. From-SVN: r237822 --- gcc/ChangeLog | 5 +++++ gcc/tree-ssa-math-opts.c | 4 ++++ 2 files changed, 9 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f88c40470e3..d9d41ad9ec1 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2016-06-28 Wilco Dijkstra + + * tree-ssa-math-opts.c (find_bswap_or_nop_1): Adjust bitnumbering + for big-endian BIT_FIELD_REF. + 2016-06-28 Pat Haugen * config/rs6000/rs6000.md ('type' attribute): Add htmsimple/dfp types. diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c index 513ef0b3f4e..d31c12fd818 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; -- 2.30.2