From 1cf83d35b8cc41e88504b38e7f4d182ee1476003 Mon Sep 17 00:00:00 2001 From: Martin Sebor Date: Tue, 12 Nov 2019 18:49:31 +0000 Subject: [PATCH] PR tree-optimization/92412 - excessive errno aliasing assumption defeats optimization gcc/ChangeLog: PR tree-optimization/92412 * targhooks.c (default_ref_may_alias_errno): Errono can only alias extern variables. gcc/testsuite/ChangeLog: PR tree-optimization/92412 * gcc.dg/strlenopt-91.c: New test. From-SVN: r278099 --- gcc/ChangeLog | 6 ++ gcc/targhooks.c | 6 +- gcc/testsuite/ChangeLog | 5 ++ gcc/testsuite/gcc.dg/strlenopt-91.c | 124 ++++++++++++++++++++++++++++ 4 files changed, 139 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/strlenopt-91.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index ddd9817690d..a434f25311c 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2019-11-12 Martin Sebor + + PR tree-optimization/92412 + * targhooks.c (default_ref_may_alias_errno): Errono can only alias + extern variables. + 2019-11-12 Martin Sebor PR middle-end/83688 diff --git a/gcc/targhooks.c b/gcc/targhooks.c index 822a0313e9e..b6443d204a6 100644 --- a/gcc/targhooks.c +++ b/gcc/targhooks.c @@ -1414,9 +1414,11 @@ default_ref_may_alias_errno (ao_ref *ref) if (TYPE_UNSIGNED (TREE_TYPE (base)) || TYPE_MODE (TREE_TYPE (base)) != TYPE_MODE (integer_type_node)) return false; - /* The default implementation assumes an errno location - declaration is never defined in the current compilation unit. */ + /* The default implementation assumes an errno location declaration + is never defined in the current compilation unit and may not be + aliased by a local variable. */ if (DECL_P (base) + && DECL_EXTERNAL (base) && !TREE_STATIC (base)) return true; else if (TREE_CODE (base) == MEM_REF diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 460ca2bbacb..584ccd7e143 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-11-12 Martin Sebor + + PR tree-optimization/92412 + * gcc.dg/strlenopt-91.c: New test. + 2019-11-12 Martin Sebor PR tree-optimization/35503 diff --git a/gcc/testsuite/gcc.dg/strlenopt-91.c b/gcc/testsuite/gcc.dg/strlenopt-91.c new file mode 100644 index 00000000000..2381d03e44a --- /dev/null +++ b/gcc/testsuite/gcc.dg/strlenopt-91.c @@ -0,0 +1,124 @@ +/* PR tree-optimization/92412 - excessive errno aliasing assumption defeats + optimization + { dg-do compile } + { dg-options "-O2 -Wall -fdump-tree-optimized" } */ + +typedef __SIZE_TYPE__ size_t; + +extern void* alloca (size_t); +extern void* calloc (size_t, size_t); +extern void* malloc (size_t); + +extern const char exta[4]; +static char stata[] = "123"; + +void sink (const void*, ...); + +#define T(ptr, alloc) do { \ + const char *p = ptr; \ + if (p[0] != '1' || p[1] != '2' || p[2] != '3' || p[3] != '\0' \ + || __builtin_strlen (p) != 3) \ + return; \ + \ + void *q = alloc; \ + __builtin_strcpy (q, p); \ + \ + if (p[0] != '1' || p[1] != '2' || p[2] != '3' || p[3] != '\0' \ + || __builtin_strlen (p) != 3 \ + || __builtin_strlen (q) != 3) \ + __builtin_abort (); \ + \ + sink (p, q); \ + } while (0) + + +void alloca_test_local (unsigned n) +{ + char loca[] = "123"; + T (loca, alloca (n)); +} + +void alloca_test_extern_const (unsigned n) +{ + T (exta, alloca (n)); +} + +void alloca_test_static (unsigned n) +{ + T (stata, alloca (n)); +} + + +// Verify fix for PR tree-optimization/92412. +void calloc_test_local (unsigned m, unsigned n) +{ + char loca[] = "123"; + T (loca, calloc (m, n)); +} + +void calloc_test_extern_const (unsigned m, unsigned n) +{ + T (exta, calloc (m, n)); +} + +void calloc_test_static (unsigned m, unsigned n) +{ + T (stata, calloc (m, n)); +} + + +// Verify fix for PR tree-optimization/92412. +void malloc_test_local (unsigned n) +{ + char loca[] = "123"; + T (loca, malloc (n)); +} + +void malloc_test_extern_const (unsigned n) +{ + T (exta, malloc (n)); +} + +void malloc_test_static (unsigned n) +{ + T (stata, malloc (n)); +} + + +#undef T +#define T(ptr, n) do { \ + const char *p = ptr; \ + if (p[0] != '1' || p[1] != '2' || p[2] != '3' || p[3] != '\0' \ + || __builtin_strlen (p) != 3) \ + return; \ + \ + char vla[n]; \ + char *q = vla; \ + __builtin_strcpy (q, p); \ + \ + if (p[0] != '1' || p[1] != '2' || p[2] != '3' || p[3] != '\0' \ + || __builtin_strlen (p) != 3 \ + || __builtin_strlen (q) != 3) \ + __builtin_abort (); \ + \ + sink (p, vla); \ + } while (0) + + +void vla_test_local (unsigned n) +{ + char loca[] = "123"; + T (loca, n); +} + +void vla_test_extern_const (unsigned n) +{ + T (exta, n); +} + +void vla_test_static (unsigned n) +{ + T (stata, n); +} + +/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */ -- 2.30.2