Tested x86_64-pc-linux-gnu, applying to trunk.
-- >8 --
When the sides of ?: are class prvalues, we wrap the COND_EXPR in a
TARGET_EXPR so that both sides will initialize the same temporary. But in
this case we were stripping the outer TARGET_EXPR and conditionally creating
different temporaries, unnecessarily using extra stack. The
recently added TARGET_EXPR_NO_ELIDE flag avoids this.
gcc/cp/ChangeLog:
* call.cc (build_conditional_expr): Set TARGET_EXPR_NO_ELIDE on the
outer TARGET_EXPR.
gcc/testsuite/ChangeLog:
* g++.dg/tree-ssa/cond-temp1.C: New test.
---
gcc/cp/call.cc | 8 +++++++-
gcc/testsuite/g++.dg/tree-ssa/cond-temp1.C | 16 ++++++++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cond-temp1.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 3506b0fcfbb..9fad3cb950b 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -6009,7 +6009,13 @@ build_conditional_expr (const op_location_t &loc,
but now we sometimes wrap them in NOP_EXPRs so the test would
fail. */
if (CLASS_TYPE_P (TREE_TYPE (result)))
- result = get_target_expr (result, complain);
+ {
+ result = get_target_expr (result, complain);
+ /* Tell gimplify_modify_expr_rhs not to strip this in
+ assignment context: we want both arms to initialize
+ the same temporary. */
+ TARGET_EXPR_NO_ELIDE (result) = true;
+ }
/* If this expression is an rvalue, but might be mistaken for an
lvalue, we must add a NON_LVALUE_EXPR. */
result = rvalue (result);
diff --git a/gcc/testsuite/g++.dg/tree-ssa/cond-temp1.C
b/gcc/testsuite/g++.dg/tree-ssa/cond-temp1.C
new file mode 100644
index 00000000000..b15635853f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/cond-temp1.C
@@ -0,0 +1,16 @@
+// Test that the ?: only creates one temporary.
+// { dg-additional-options "-fdump-tree-gimple" }
+// { dg-final { scan-tree-dump-times "struct A" 2 "gimple" } }
+
+struct A
+{
+ int i;
+ A(int);
+};
+
+bool b;
+int main()
+{
+ A a = 1;
+ a = b ? A(2) : A(3);
+}
base-commit: af9034827e8f06f10767064e9fc7443b94e08184
--
2.31.1
