The following patch fixes https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91223
The patch was successfully bootstrapped and tested on x86-64. Committed as rev. 273810.
Index: ChangeLog =================================================================== --- ChangeLog (revision 273809) +++ ChangeLog (working copy) @@ -1,3 +1,9 @@ +2019-07-25 Vladimir Makarov <vmaka...@redhat.com> + + PR rtl-optimization/91223 + * lra-constraints.c (process_alt_operands): Fail for unsuccessful + matching with INOUT operand. + 2019-07-25 Eric Botcazou <ebotca...@adacore.com> * stmt.c (expand_case): Try to narrow the index type if it's larger Index: lra-constraints.c =================================================================== --- lra-constraints.c (revision 273809) +++ lra-constraints.c (working copy) @@ -2171,6 +2171,14 @@ process_alt_operands (int only_alternati } else { + /* If the operands do not match and one + operand is INOUT, we can not match them. + Try other possibilities, e.g. other + alternatives or commutative operand + exchange. */ + if (curr_static_id->operand[nop].type == OP_INOUT + || curr_static_id->operand[m].type == OP_INOUT) + break; /* Operands don't match. If the operands are different user defined explicit hard registers, then we cannot make them match Index: testsuite/ChangeLog =================================================================== --- testsuite/ChangeLog (revision 273809) +++ testsuite/ChangeLog (working copy) @@ -1,3 +1,8 @@ +2019-07-25 Vladimir Makarov <vmaka...@redhat.com> + + PR rtl-optimization/91223 + * gcc.target/i386/pr91223.c: New test. + 2019-07-25 Iain Sandoe <i...@sandoe.co.uk> PR gcov-profile/91087 Index: testsuite/gcc.target/i386/pr91223.c =================================================================== --- testsuite/gcc.target/i386/pr91223.c (nonexistent) +++ testsuite/gcc.target/i386/pr91223.c (working copy) @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-Og -fno-tree-fre" } */ +int a; +void fn2(short, short); + +void fn1(void) { + short b[8]; + b[0] |= a & 3; + b[1] = a; + fn2(b[0], b[1]); +}