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
