http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58253
Bug ID: 58253
Summary: IPA-SRA creates aligned loads from unaligned memory
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: amylaar at gcc dot gnu.org
CC: amylaar at gcc dot gnu.org, jamborm at gcc dot gnu.org,
rguenth at gcc dot gnu.org
Depends on: 52402
Target: epiphany-*-*
+++ This bug was initially created as a clone of Bug #52402 +++
What I see on epiphany (at O2 and above, enabling SRA) for
gcc.dg/torture/pr52402.c is that the call of foo.isra.0 in main is done
using an aligned type:
Breakpoint 5, epiphany_function_arg (cum_v=..., mode=TImode, type=0xb7c5f960,
named=true)
at /home/amylaar/adapteva/git/sdk/srcw/gcc/config/epiphany/epiphany.c:2177
2177 CUMULATIVE_ARGS cum = *get_cumulative_args (cum_v);
(gdb) call debug_tree(type)
<vector_type 0xb7c5f960
type <integer_type 0xb7bed360 int public SI
size <integer_cst 0xb7bdd104 constant 32>
unit size <integer_cst 0xb7bdd118 constant 4>
align 32 symtab 0 alias set 3 canonical type 0xb7bed360 precision 32
min <integer_cst 0xb7bdd2f8 -2147483648> max <integer_cst 0xb7bdd30c
2147483647>
pointer_to_this <pointer_type 0xb7beda80>>
TI
size <integer_cst 0xb7bdd460 type <integer_type 0xb7bed060 bitsizetype>
constant 128>
unit size <integer_cst 0xb7bdd474 type <integer_type 0xb7bed000 sizetype>
constant 16>
align 64 symtab 0 alias set 3 canonical type 0xb7c5f960 nunits 4 context
<translation_unit_decl 0xb7bf2e58 D.1323>
pointer_to_this <pointer_type 0xb7c5fba0>>
but when the callee foo.isra.0 was compiled before, it got allegedly passed
an unaligned type:
Breakpoint 5, epiphany_function_arg (cum_v=..., mode=TImode, type=0xb7c6f300,
named=true)
at /home/amylaar/adapteva/git/sdk/srcw/gcc/config/epiphany/epiphany.c:2177
2177 CUMULATIVE_ARGS cum = *get_cumulative_args (cum_v);
(gdb) call debug_tree(type)
<vector_type 0xb7c6f300 v4si
type <integer_type 0xb7bed360 int public SI
size <integer_cst 0xb7bdd104 constant 32>
unit size <integer_cst 0xb7bdd118 constant 4>
align 32 symtab 0 alias set 3 canonical type 0xb7bed360 precision 32
min <integer_cst 0xb7bdd2f8 -2147483648> max <integer_cst 0xb7bdd30c
2147483647>
pointer_to_this <pointer_type 0xb7beda80>>
TI
size <integer_cst 0xb7bdd460 type <integer_type 0xb7bed060 bitsizetype>
constant 128>
unit size <integer_cst 0xb7bdd474 type <integer_type 0xb7bed000 sizetype>
constant 16>
align 8 symtab 0 alias set -1 canonical type 0xb7c5f960 nunits 4 context
<translation_unit_decl 0xb7bf2e58 D.1323>>
When passing 64-bit aligned types, the epiphany ABI uses register pair(s)
to enable double load-store, thus in this case where r0 has already been
used, the argument starts at r2; in the less-aligned case, it starts at
r1. Thus, the callee expects the argument in a different place than where
it has been put by the caller.
Richard Biener:
:So you say that on Epiphany the ABI of the function depends on the actual
:argument alignment? And this alignment is taken from the _argument_, not
:the type of the function prototype?
Note, these are the types as passed to TARGET_FUNCTION_ARG.
The original function prototype is no longer in the picture because
the ipa optimizers have used a cloned/specialized function instead,
and the types used when constructing the call are not the same as when
generating the callee.
