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| author | Alexandre Oliva <aoliva@gcc.gnu.org> | 2018-09-20 19:34:44 +0000 |
|---|---|---|
| committer | Alexandre Oliva <aoliva@gcc.gnu.org> | 2018-09-20 19:34:44 +0000 |
| commit | 468e1ef4be47810052687c8193d106e591c74bc4 (patch) | |
| tree | 420d98d2ccab135a9a94d7371b6f9f0f1ae6acd6 | |
| parent | 894f597f8fb8693a5d0f5834e98a8ccebbbb9106 (diff) | |
| download | gcc-468e1ef4be47810052687c8193d106e591c74bc4.zip gcc-468e1ef4be47810052687c8193d106e591c74bc4.tar.gz gcc-468e1ef4be47810052687c8193d106e591c74bc4.tar.bz2 | |
[PR87054] fix unaligned access
Building an ADDR_EXPR uses the canonical type to build the pointer
type, but then, as we dereference it, we lose track of lax alignment
known to apply to the dereferenced object. This might not be a
problem in general, but it is when the compiler implicitly introduces
address taking and dereferencing, as it does for asm statements, and
as it may do in some loop optimizations.
From: Richard Biener <rguenther@suse.de>
for gcc/ChangeLog
PR middle-end/87054
* gimplify.c (gimplify_expr): Retain alignment of
addressable lvalue in dereference.
From: Alexandre Oliva <oliva@adacore.com>
for gcc/testsuite/ChangeLog
PR middle-end/87054
* gcc.dg/pr87054.c: New.
From-SVN: r264450
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/gimplify.c | 8 | ||||
| -rw-r--r-- | gcc/testsuite/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/pr87054.c | 29 |
4 files changed, 47 insertions, 1 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 641e359..361dfc4 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2018-09-20 Richard Biener <rguenther@suse.de> + + PR middle-end/87054 + * gimplify.c (gimplify_expr): Retain alignment of + addressable lvalue in dereference. + 2018-09-20 Alexandre Oliva <aoliva@redhat.com> PR bootstrap/87013 diff --git a/gcc/gimplify.c b/gcc/gimplify.c index f0eb04a..509fc2f 100644 --- a/gcc/gimplify.c +++ b/gcc/gimplify.c @@ -12538,9 +12538,15 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p, /* An lvalue will do. Take the address of the expression, store it in a temporary, and replace the expression with an INDIRECT_REF of that temporary. */ + tree ref_alias_type = reference_alias_ptr_type (*expr_p); + unsigned int ref_align = get_object_alignment (*expr_p); + tree ref_type = TREE_TYPE (*expr_p); tmp = build_fold_addr_expr_loc (input_location, *expr_p); gimplify_expr (&tmp, pre_p, post_p, is_gimple_reg, fb_rvalue); - *expr_p = build_simple_mem_ref (tmp); + if (TYPE_ALIGN (ref_type) != ref_align) + ref_type = build_aligned_type (ref_type, ref_align); + *expr_p = build2 (MEM_REF, ref_type, + tmp, build_zero_cst (ref_alias_type)); } else if ((fallback & fb_rvalue) && is_gimple_reg_rhs_or_call (*expr_p)) { diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index c7c8e90..a0a08a4 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2018-09-20 Alexandre Oliva <oliva@adacore.com> + + PR middle-end/87054 + * gcc.dg/pr87054.c: New. + 2018-09-20 Richard Sandiford <richard.sandiford@arm.com> PR tree-optimization/87288 diff --git a/gcc/testsuite/gcc.dg/pr87054.c b/gcc/testsuite/gcc.dg/pr87054.c new file mode 100644 index 0000000..4ca2b62 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr87054.c @@ -0,0 +1,29 @@ +// { dg-do run } +// { dg-options "-O2" } + +#ifndef T +# ifdef __SSE__ +# define T __int128 +# else +# define T long +# endif +#endif +#ifndef R +# ifdef __SSE__ +# define R "x" +# else +# define R "r" +# endif +#endif + + +typedef T A; // #define T to long or __int128 +struct B { char d; A c; } __attribute__((packed)); +struct B b[50]; // many elements to avoid loop unrolling + +int main () { + int i; + for (i = 0; i < sizeof(b) / sizeof(*b); i++) { + asm ("" : "+" R (b[i].c)); // #define R to "r" on ppc or "x" on x86_64 + } +} |