This avoids a tempoary when gimplifying reg = a ? b : c, re-using the LHS of an assignment if that's a register.
Re-bootstrap and regtest running on x86_64-unknown-linux-gnu. PR middle-end/27800 * gimplify.cc (gimplify_modify_expr_rhs): For a COND_EXPR avoid a temporary from gimplify_cond_expr when the LHS is a register by pushing the assignment into the COND_EXPR arms. * gcc.dg/pr27800.c: New testcase. --- gcc/gimplify.cc | 7 +++++-- gcc/testsuite/gcc.dg/pr27800.c | 11 +++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr27800.c diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc index 763843f45a7..26e96ada4c7 100644 --- a/gcc/gimplify.cc +++ b/gcc/gimplify.cc @@ -6082,8 +6082,11 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, /* If we're assigning to a non-register type, push the assignment down into the branches. This is mandatory for ADDRESSABLE types, since we cannot generate temporaries for such, but it saves a - copy in other cases as well. */ - if (!is_gimple_reg_type (TREE_TYPE (*from_p))) + copy in other cases as well. + Also avoid an extra temporary and copy when assigning to + a register. */ + if (!is_gimple_reg_type (TREE_TYPE (*from_p)) + || (is_gimple_reg (*to_p) && !gimplify_ctxp->allow_rhs_cond_expr)) { /* This code should mirror the code in gimplify_cond_expr. */ enum tree_code code = TREE_CODE (*expr_p); diff --git a/gcc/testsuite/gcc.dg/pr27800.c b/gcc/testsuite/gcc.dg/pr27800.c new file mode 100644 index 00000000000..e92ebc22e6f --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr27800.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-fdump-tree-gimple" } */ + +int iii (int a, int b, int c) +{ + return a ? b : c; +} + +/* Verify we end up with two assignments and not an extra copy + resulting from another temporary generated from gimplify_cond_expr. */ +/* { dg-final { scan-tree-dump-times " = " 2 "gimple" } } */ -- 2.35.3