From eec3a65ed638a1c58fa08ddf508d2d60b64d311d Mon Sep 17 00:00:00 2001 From: Eric Botcazou Date: Wed, 11 Jan 2023 15:58:47 +0100 Subject: [PATCH] Fix problematic interaction between bitfields, unions, SSO and SRA The handling of bitfields by the SRA pass is peculiar and this must be taken into account to support the scalar_storage_order attribute. gcc/ PR tree-optimization/108199 * tree-sra.cc (sra_modify_expr): Deal with reverse storage order for bit-field references. gcc/testsuite/ * gcc.dg/sso-17.c: New test. --- gcc/testsuite/gcc.dg/sso-17.c | 52 +++++++++++++++++++++++++++++++++++ gcc/tree-sra.cc | 18 +++++++++++- 2 files changed, 69 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/sso-17.c diff --git a/gcc/testsuite/gcc.dg/sso-17.c b/gcc/testsuite/gcc.dg/sso-17.c new file mode 100644 index 000000000000..67e2d3793fde --- /dev/null +++ b/gcc/testsuite/gcc.dg/sso-17.c @@ -0,0 +1,52 @@ +/* { dg-do run } */ +/* { dg-options "-O2" } */ + +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ +#define REV_ENDIANNESS __attribute__((scalar_storage_order("big-endian"))) +#else +#define REV_ENDIANNESS __attribute__((scalar_storage_order("little-endian"))) +#endif + +typedef unsigned long long u64; + +union DST { + u64 val; + + struct { + u64 x : 1; + u64 y : 1; + u64 r: 62; + } REV_ENDIANNESS; +} REV_ENDIANNESS; + + +struct SRC { + u64 a; +} REV_ENDIANNESS; + +[[gnu::noipa]] +void foo () {__builtin_abort();} + +[[gnu::noinline]] +int bar(struct SRC *src) +{ + union DST dst; + + dst.val = src->a; + + if (dst.y) { + foo(); + } + return 0; +} + +int main(void) +{ +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + struct SRC t = {-1ull & (~(0x01ull<<62))}; +#else + struct SRC t = {-1ull & (~(0x01ull<<1))}; +#endif + bar(&t); + return 0; +} diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc index 95291e8df934..09dbd7be77fe 100644 --- a/gcc/tree-sra.cc +++ b/gcc/tree-sra.cc @@ -3858,7 +3858,23 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write) } } else - *expr = repl; + { + /* If we are going to replace a scalar field in a structure with + reverse storage order by a stand-alone scalar, we are going to + effectively byte-swap the scalar and we also need to byte-swap + the portion of it represented by the bit-field. */ + if (bfr && REF_REVERSE_STORAGE_ORDER (bfr)) + { + REF_REVERSE_STORAGE_ORDER (bfr) = 0; + TREE_OPERAND (bfr, 2) + = size_binop (MINUS_EXPR, TYPE_SIZE (TREE_TYPE (repl)), + size_binop (PLUS_EXPR, TREE_OPERAND (bfr, 1), + TREE_OPERAND (bfr, 2))); + } + + *expr = repl; + } + sra_stats.exprs++; } else if (write && access->grp_to_be_debug_replaced) -- 2.47.2