A fix for pr85753 I committed back in may introduced a subtle logic error that cause false positives for copies involving unknown offsets into non-array objects. The attached patch corrects this mistake. I have committed it as obvious in r266967 after verifying it on x86_64-linux. The committed patch is attached.
Martin
PR tree-optimization/86196 - Bogus -Wrestrict on memcpy between array elements at unequal indices gcc/ChangeLog: PR tree-optimization/86196 * gimple-ssa-warn-restrict.c (builtin_memref::builtin_memref): Use base size only of arrays. gcc/testsuite/ChangeLog: PR tree-optimization/86196 * gcc.dg/Wrestrict-18.c: New test. Index: gcc/gimple-ssa-warn-restrict.c =================================================================== --- gcc/gimple-ssa-warn-restrict.c (revision 266963) +++ gcc/gimple-ssa-warn-restrict.c (working copy) @@ -272,15 +272,16 @@ builtin_memref::builtin_memref (tree expr, tree si offset_int maxoff = maxobjsize; tree basetype = TREE_TYPE (base); - if (TREE_CODE (basetype) == ARRAY_TYPE - && ref - && array_at_struct_end_p (ref)) - ; /* Use the maximum possible offset for last member arrays. */ - else if (tree basesize = TYPE_SIZE_UNIT (basetype)) - if (TREE_CODE (basesize) == INTEGER_CST) - /* Size could be non-constant for a variable-length type such - as a struct with a VLA member (a GCC extension). */ - maxoff = wi::to_offset (basesize); + if (TREE_CODE (basetype) == ARRAY_TYPE) + { + if (ref && array_at_struct_end_p (ref)) + ; /* Use the maximum possible offset for last member arrays. */ + else if (tree basesize = TYPE_SIZE_UNIT (basetype)) + if (TREE_CODE (basesize) == INTEGER_CST) + /* Size could be non-constant for a variable-length type such + as a struct with a VLA member (a GCC extension). */ + maxoff = wi::to_offset (basesize); + } if (offrange[0] >= 0) { Index: gcc/testsuite/gcc.dg/Wrestrict-18.c =================================================================== --- gcc/testsuite/gcc.dg/Wrestrict-18.c (nonexistent) +++ gcc/testsuite/gcc.dg/Wrestrict-18.c (working copy) @@ -0,0 +1,37 @@ +/* PR tree-optimization/86196 - Bogus -Wrestrict on memcpy between array + elements at unequal indices + { dg-do compile } + { dg-options "-O2 -Wall" } */ + +typedef __SIZE_TYPE__ size_t; + +extern void* memcpy (void*, const void*, size_t); + +struct S +{ + int n; + void * p; +}; + +/* Test case submitted in the PR. */ + +void pr86196_c0 (struct S * a, size_t n) +{ + for (size_t i = 0, j = 0; i != n; ++i) + { + if (a[i].n == 0) + { + if (i != j) + memcpy (&a[j], &a[i], sizeof (struct S)); /* { dg-bogus "\\\[-Wrestrict" } */ + ++j; + } + } +} + +/* Reduced test case. */ + +void pr86196_c1 (struct S *a, int i, int j) +{ + if (i != j) + memcpy (&a[j], &a[i], sizeof (struct S)); /* { dg-bogus "\\\[-Wrestrict" } */ +}