Hi Nathan! Thanks for looking into this. When I reported this, <http://news.gmane.org/find-root.php?message_id=%3C87fv3is74z.fsf%40schwinge.name%3E>, quite a lot of testcases had been failing -- with recent GCC trunk, the number is smaller (because of other middle end/optimization changes, I suppose). Yet, the problem still can be observed; grep for "%retval" in g++.log.
On Thu, 8 Oct 2015 13:33:55 -0400, Nathan Sidwell <nat...@acm.org> wrote:
> I've committed this to trunk. The C++ ABI now returns a pointer to the
> passed-in artificial arg that points to the return area. consequently
> return-in-mem and type_mode(return_type) == VOIDmode are not tautologies.
> * config/nvptx/nvptx.c (nvptx_declare_function_name): Functions
> may return pointer as well as in memory.
> (nvptx_output_return): Likewise.
Hmm, but what I now see happening is that now there is incorrect
"%out_retval" usage (but it's not part of the function prototypes), for
example:
$ build-gcc/gcc/xg++ -Bbuild-gcc/gcc/
source-gcc/gcc/testsuite/g++.dg/ipa/ipa-icf-6.C -std=gnu++98 -O3 -o
ipa-icf-6.exe -S
Diff before/after your change:
$ diff -U4 O/ipa-icf-6.exe ipa-icf-6.exe
--- O/ipa-icf-6.exe 2015-10-06 18:30:21.581187448 +0200
+++ ipa-icf-6.exe 2015-10-09 07:49:23.894893180 +0200
@@ -10,8 +10,9 @@
.visible .func _Z5test21A(.param.u64 %in_ar1, .param.u64 %in_ar2)
{
.reg.u64 %ar2;
.reg.u64 %ar1;
+ .reg.u64 %retval;
.reg.u64 %hr10;
.reg.u64 %r25;
.reg.u64 %r26;
.reg.u64 %r27;
@@ -28,8 +29,9 @@
}
$L2:
st.u64 [%r25+8], %r25;
mov.u64 %retval, %r25;
+ st.param.u64 [%out_retval], %retval;
ret;
}
// BEGIN FUNCTION DECL: _ZL7test_mePF1AS_E
.func _ZL7test_mePF1AS_E(.param.u64 %in_ar1);
@@ -78,8 +80,9 @@
.visible .func _Z5test11A(.param.u64 %in_ar1, .param.u64 %in_ar2)
{
.reg.u64 %ar2;
.reg.u64 %ar1;
+ .reg.u64 %retval;
.reg.u64 %hr10;
.reg.u64 %r25;
.reg.u64 %r26;
.reg.u64 %r27;
@@ -96,8 +99,9 @@
}
$L6:
st.u64 [%r25+8], %r25;
mov.u64 %retval, %r25;
+ st.param.u64 [%out_retval], %retval;
ret;
}
// BEGIN GLOBAL FUNCTION DECL: main
.visible .func (.param.u32 %out_retval)main(.param.u32 %argc, .param.u64
%argv);
(I have not yet made an attempt at trying to understand the problem.)
For reference:
> Index: gcc/config/nvptx/nvptx.c
> ===================================================================
> --- gcc/config/nvptx/nvptx.c (revision 228617)
> +++ gcc/config/nvptx/nvptx.c (working copy)
> @@ -531,13 +531,8 @@ nvptx_declare_function_name (FILE *file,
> nvptx_write_function_decl (s, name, decl);
> fprintf (file, "%s", s.str().c_str());
>
> - bool return_in_mem = false;
> - if (TYPE_MODE (result_type) != VOIDmode)
> - {
> - machine_mode mode = TYPE_MODE (result_type);
> - if (!RETURN_IN_REG_P (mode))
> - return_in_mem = true;
> - }
> + bool return_in_mem = (TYPE_MODE (result_type) != VOIDmode
> + && !RETURN_IN_REG_P (TYPE_MODE (result_type)));
>
> fprintf (file, "\n{\n");
>
> @@ -547,9 +542,13 @@ nvptx_declare_function_name (FILE *file,
> false, return_in_mem);
> if (return_in_mem)
> fprintf (file, "\t.reg.u%d %%ar1;\n", GET_MODE_BITSIZE (Pmode));
> - else if (TYPE_MODE (result_type) != VOIDmode)
> +
> + /* C++11 ABI causes us to return a reference to the passed in
> + pointer for return_in_mem. */
> + if (cfun->machine->ret_reg_mode != VOIDmode)
> {
> - machine_mode mode = arg_promotion (TYPE_MODE (result_type));
> + machine_mode mode = arg_promotion
> + ((machine_mode)cfun->machine->ret_reg_mode);
> fprintf (file, "\t.reg%s %%retval;\n",
> nvptx_ptx_type_from_mode (mode, false));
> }
> @@ -635,17 +634,13 @@ nvptx_declare_function_name (FILE *file,
> const char *
> nvptx_output_return (void)
> {
> - tree fntype = TREE_TYPE (current_function_decl);
> - tree result_type = TREE_TYPE (fntype);
> - if (TYPE_MODE (result_type) != VOIDmode)
> + machine_mode mode = (machine_mode)cfun->machine->ret_reg_mode;
> +
> + if (mode != VOIDmode)
> {
> - machine_mode mode = TYPE_MODE (result_type);
> - if (RETURN_IN_REG_P (mode))
> - {
> - mode = arg_promotion (mode);
> - fprintf (asm_out_file, "\tst.param%s\t[%%out_retval], %%retval;\n",
> - nvptx_ptx_type_from_mode (mode, false));
> - }
> + mode = arg_promotion (mode);
> + fprintf (asm_out_file, "\tst.param%s\t[%%out_retval], %%retval;\n",
> + nvptx_ptx_type_from_mode (mode, false));
> }
>
> return "ret;";
> Index: gcc/config/nvptx/nvptx.h
> ===================================================================
> --- gcc/config/nvptx/nvptx.h (revision 228617)
> +++ gcc/config/nvptx/nvptx.h (working copy)
> @@ -228,7 +228,7 @@ struct GTY(()) machine_function
> bool has_call_with_varargs;
> bool has_call_with_sc;
> HOST_WIDE_INT outgoing_stdarg_size;
> - int ret_reg_mode;
> + int ret_reg_mode; /* machine_mode not defined yet. */
> int punning_buffer_size;
> };
> #endif
Grüße,
Thomas
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