The following patch fixes https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82556
The patch was bootstrapped and tested on x86-64. Committed to trunk as rev. 253862. Committed to gcc-7-branch as rev. 253863.
Index: ChangeLog =================================================================== --- ChangeLog (revision 253862) +++ ChangeLog (working copy) @@ -1,3 +1,9 @@ +2017-10-18 Vladimir Makarov <vmaka...@redhat.com> + + PR middle-end/82556 + * lra-constraints.c (curr_insn_transform): Use non-input operand + instead of output one for matched reload. + 2017-10-17 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/82549 Index: testsuite/ChangeLog =================================================================== --- testsuite/ChangeLog (revision 253862) +++ testsuite/ChangeLog (working copy) @@ -1,3 +1,8 @@ +2017-10-18 Vladimir Makarov <vmaka...@redhat.com> + + PR middle-end/82556 + * gcc.target/i386/pr82556.c: New. + 2017-10-17 Eric Botcazou <ebotca...@adacore.com> * gcc.dg/attr-alloc_size-11.c: UnXFAIL for visium-*-*. Index: lra-constraints.c =================================================================== --- lra-constraints.c (revision 253815) +++ lra-constraints.c (working copy) @@ -4284,7 +4284,13 @@ curr_insn_transform (bool check_only_p) } else if (curr_static_id->operand[i].type == OP_IN && (curr_static_id->operand[goal_alt_matched[i][0]].type - == OP_OUT)) + == OP_OUT + || (curr_static_id->operand[goal_alt_matched[i][0]].type + == OP_INOUT + && (operands_match_p + (*curr_id->operand_loc[i], + *curr_id->operand_loc[goal_alt_matched[i][0]], + -1))))) { /* generate reloads for input and matched outputs. */ match_inputs[0] = i; @@ -4295,9 +4301,14 @@ curr_insn_transform (bool check_only_p) [goal_alt_number * n_operands + goal_alt_matched[i][0]] .earlyclobber); } - else if (curr_static_id->operand[i].type == OP_OUT + else if ((curr_static_id->operand[i].type == OP_OUT + || (curr_static_id->operand[i].type == OP_INOUT + && (operands_match_p + (*curr_id->operand_loc[i], + *curr_id->operand_loc[goal_alt_matched[i][0]], + -1)))) && (curr_static_id->operand[goal_alt_matched[i][0]].type - == OP_IN)) + == OP_IN)) /* Generate reloads for output and matched inputs. */ match_reload (i, goal_alt_matched[i], outputs, goal_alt[i], &before, &after, curr_static_id->operand_alternative Index: testsuite/gcc.target/i386/pr82556.c =================================================================== --- testsuite/gcc.target/i386/pr82556.c (nonexistent) +++ testsuite/gcc.target/i386/pr82556.c (working copy) @@ -0,0 +1,19 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fno-strict-aliasing -fwrapv -fexcess-precision=standard" } */ +extern int foo(); +typedef struct { + char id; + unsigned char fork_flags; + short data_length; +} Header; +int a; +void X() { + do { + char* b; + Header c; + if (a) + c.fork_flags |= 1; + __builtin_memcpy(b, &c, __builtin_offsetof(Header, data_length)); + b += foo(); + } while (1); +}