The x86_64 psABI says that an empty class isn't passed or returned in memory or
registers, so we shouldn't set %eax in this function. Is this a reasonable
place to implement that? Another possibility would be to remove the hack to
prevent i386.c:function_value_64 from returning NULL in this case and fix the
callers to deal, but that seems like more work.
The df-scan hunk catches the case where we look at a 0-length reg and build
a range the length of unsigned int, which happened before I changed
assign_parms to match expand_function_end.
Tested x86_64-pc-linux-gnu. OK for trunk?
PR target/88529
gcc/ChangeLog:
* df-scan.c (df_ref_record): Check that regno < endregno.
* function.c (assign_parms, expand_function_end): Do nothing with a
TYPE_EMPTY_P result.
gcc/testsuite/ChangeLog:
* g++.target/i386/empty-class1.C: New test.
---
gcc/df-scan.c | 2 ++
gcc/function.c | 16 ++++++++++------
gcc/testsuite/g++.target/i386/empty-class1.C | 9 +++++++++
3 files changed, 21 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.target/i386/empty-class1.C
diff --git a/gcc/df-scan.c b/gcc/df-scan.c
index 1268536b3f0..e9da64ff3df 100644
--- a/gcc/df-scan.c
+++ b/gcc/df-scan.c
@@ -2595,6 +2595,8 @@ df_ref_record (enum df_ref_class cl,
ref_flags |= DF_REF_PARTIAL;
ref_flags |= DF_REF_MW_HARDREG;
+ gcc_assert (regno < endregno);
+
hardreg = problem_data->mw_reg_pool->allocate ();
hardreg->type = ref_type;
hardreg->flags = ref_flags;
diff --git a/gcc/function.c b/gcc/function.c
index 67576950983..6abaf3d116f 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -3821,9 +3821,11 @@ assign_parms (tree fndecl)
tree decl_result = DECL_RESULT (fndecl);
rtx decl_rtl = DECL_RTL (decl_result);
- if (REG_P (decl_rtl)
- ? REGNO (decl_rtl) >= FIRST_PSEUDO_REGISTER
- : DECL_REGISTER (decl_result))
+ if ((REG_P (decl_rtl)
+ ? REGNO (decl_rtl) >= FIRST_PSEUDO_REGISTER
+ : DECL_REGISTER (decl_result))
+ /* Unless the psABI says not to. */
+ && !TYPE_EMPTY_P (TREE_TYPE (decl_result)))
{
rtx real_decl_rtl;
@@ -5410,9 +5412,11 @@ expand_function_end (void)
tree decl_result = DECL_RESULT (current_function_decl);
rtx decl_rtl = DECL_RTL (decl_result);
- if (REG_P (decl_rtl)
- ? REGNO (decl_rtl) >= FIRST_PSEUDO_REGISTER
- : DECL_REGISTER (decl_result))
+ if ((REG_P (decl_rtl)
+ ? REGNO (decl_rtl) >= FIRST_PSEUDO_REGISTER
+ : DECL_REGISTER (decl_result))
+ /* Unless the psABI says not to. */
+ && !TYPE_EMPTY_P (TREE_TYPE (decl_result)))
{
rtx real_decl_rtl = crtl->return_rtx;
complex_mode cmode;
diff --git a/gcc/testsuite/g++.target/i386/empty-class1.C
b/gcc/testsuite/g++.target/i386/empty-class1.C
new file mode 100644
index 00000000000..c1992772d26
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/empty-class1.C
@@ -0,0 +1,9 @@
+// PR target/88529
+// { dg-do compile { target { c++11 && x86_64-*-* } } }
+// { dg-additional-options -fdump-rtl-expand }
+// { dg-final { scan-rtl-dump-not "set" "expand" } }
+// The x86_64 psABI says that f() doesn't put the return value anywhere.
+
+class A{};
+
+A f() { return {}; }
base-commit: 08ce1f4c5091b80b680d15c53a17237544a3cca8
prerequisite-patch-id: 320d08bee3615919d0cf6a9d33bc2247aece51c7
--
2.27.0
