https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102554
Bug ID: 102554
Summary: [ 10/11/12 Regresion ] Inlining missed at -O3 with
non-default --param=early-inlining-insns and pragma
optimize
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: jschoen4 at gmail dot com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
GNU C++14 (GCC) version 10.2.0 (x86_64-pc-linux-gnu)
compiled by GNU C version 10.2.0, GMP version 6.0.0, MPFR version
3.1.1, MPC version 1.0.1, isl version isl-0.16.1-GMP
Target: x86_64-pc-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.2.0 (GCC)
===========
=TEST CODE=
===========
cat test.cpp
#pragma GCC push_options
#pragma GCC optimize ("no-lifetime-dse")
class TestClass
{
public:
static inline int should_inline() {
return 10;
}
};
#pragma GCC pop_options
int main() {
return TestClass::should_inline() + 1;
}
===========
=cmd =
===========
gcc-10 test.cpp -S --param=early-inlining-insns=30 -O3 -fno-lifetime-dse -Wall
-Wextra
===========
=BAD ASM =
===========
cat test.s
.file "test.cpp"
.text
.section
.text._ZN9TestClass13should_inlineEv,"axG",@progbits,_ZN9TestClass13should_inlineEv,comdat
.p2align 4
.weak _ZN9TestClass13should_inlineEv
.type _ZN9TestClass13should_inlineEv, @function
_ZN9TestClass13should_inlineEv:
.LFB0:
.cfi_startproc
movl $10, %eax
ret
.cfi_endproc
.LFE0:
.size _ZN9TestClass13should_inlineEv,
.-_ZN9TestClass13should_inlineEv
.section .text.startup,"ax",@progbits
.p2align 4
.globl main
.type main, @function
main:
.LFB1:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
call _ZN9TestClass13should_inlineEv
addq $8, %rsp
.cfi_def_cfa_offset 8
addl $1, %eax
ret
.cfi_endproc
.LFE1:
.size main, .-main
.ident "GCC: (GNU) 10.2.0"
.section .note.GNU-stack,"",@progbits
===========
=info =
===========
cat test.cpp.079i.inline
...
Deciding on inlining of small functions. Starting with size 9.
Enqueueing calls in int main()/1.
test.cpp:13:34: missed: not inlinable: int main()/1 -> static int
TestClass::should_inline()/0, optimization level attribute mismatch
param_early_inlining_insns (0x1e/0xe)
Enqueueing calls in static int TestClass::should_inline()/0.
node context cache: 0 hits, 0 misses, 1 initializations
...
===========
=GOOD ASM =
===========
gcc-10 test.cpp -S --param=early-inlining-insns=14 -O3 -fno-lifetime-dse -Wall
-Wextra
.file "test.cpp"
.text
.section .text.startup,"ax",@progbits
.p2align 4
.globl main
.type main, @function
main:
.LFB1:
.cfi_startproc
movl $11, %eax
ret
.cfi_endproc
.LFE1:
.size main, .-main
.ident "GCC: (GNU) 10.2.0"
.section .note.GNU-stack,"",@progbits
==========
=notes=
==========
Starting with gcc 10+ (gcc9 works correctly), the use of
--param=early-inlining-insns=30 and -O3 on the command line combined with using
a "#pragma GCC optimize" in source code, even one that does not change the
effective optimization attributes, causes "optimization level attribute
mismatch" to occur in the inliner.
In the example I placed both -fno-lifetime-dse on the command line and in the
pragma gcc optimize ("no-lifetime-dse"), so it has no impact at all to the
effective optimization attributes.
The issue is not specific to using just pragma GCC optimize "no-lifetime-dse",
any pragma gcc optimize line will have this effect. Even "unrecognized" ones.
i.e.
#pragma GCC optimize ("fake_attribute")
Any value OTHER THAN --param=early-inlining-insns=14 on the command line when
used with -O3 and pragma optimize will trigger this.
.. i.e.
======================
=optimize correctly =
======================
gcc-10 test.cpp -S --param=early-inlining-insns=14 -O3 -fno-lifetime-dse -Wall
-Wextra
gcc-10 test.cpp -S --param=early-inlining-insns=30 -O2 -fno-lifetime-dse -Wall
-Wextra
gcc-9 test.cpp -S --param=early-inlining-insns=30 -O3 -fno-lifetime-dse -Wall
-Wextra
======================
=missed optimize =
======================
gcc-10 test.cpp -S --param=early-inlining-insns=12 -O3 -fno-lifetime-dse -Wall
-Wextra
gcc-10 test.cpp -S --param=early-inlining-insns=17 -O3 -fno-lifetime-dse -Wall
-Wextra
etc.
gcc-11 test.cpp -S --param=early-inlining-insns=30 -O3 -fno-lifetime-dse -Wall
-Wextra
gcc-12 test.cpp -S --param=early-inlining-insns=30 -O3 -fno-lifetime-dse -Wall
-Wextra
gcc-trunk test.cpp -S --param=early-inlining-insns=30 -O3 -fno-lifetime-dse
-Wall -Wextra
Code path where CIF_OPTIMIZATION_MISMATCH is being set.
gcc/ipa-inline.c:
568 can_early_inline_edge_p (struct cgraph_edge *e)
...
593 if (!can_inline_edge_p (e, true, true)
594 || !can_inline_edge_by_limits_p (e, true, false, true))
-------->
428 can_inline_edge_by_limits_p (struct cgraph_edge *e, bool report,
429 bool disregard_limits = false, bool early
= false)
...
524 /* When user added an attribute to the callee honor it. */
525 else if (lookup_attribute ("optimize", DECL_ATTRIBUTES
(callee->decl))
526 && opts_for_fn (caller->decl) != opts_for_fn
(callee->decl))
527 {
528 e->inline_failed = CIF_OPTIMIZATION_MISMATCH;
529 inlinable = false;
530 }
I suspect the change that moved the --params= options into the cl_optimization
struct is related to this misssed optimization.
