在 2023/12/23 下午6:44, Xi Ruoyao 写道:
On Sat, 2023-12-23 at 10:29 +0800, chenglulu wrote:
The performance drop has nothing to do with this patch. I found that the h264
performance compiled
by r14-6787 compared to r14-6421 dropped by 6.4%.
Then I guess we should create a bug report...
The code h264 score in r14-6818 is the same as that of r14-6421.
But there is a problem. My regression test has the following two fail
items.(based on r14-6787)
+FAIL: gcc.dg/cpp/_Pragma3.c (test for excess errors)
+FAIL: gcc.dg/pr86617.c scan-rtl-dump-times final "mem/v" 6
Strange. I didn't see them on r14-6650 (with or without the patch).
+FAIL: gcc.dg/pr86617.c scan-rtl-dump-times final "mem/v" 6
In r14-6818 the issue persists. I kind of chased the code and found that the
problem is like this:
volatile unsigned char u8;
void test (void)
{
u8 = u8 + u8;
u8 = u8 - u8;
}
$./gcc/cc1 test.c -o test.s -fdump-rtl-all-all -fdiagnostics-plain-output -Os
-fdump-rtl-final -ffat-lto-objects
test.c.301r.outof_cfglayout
(insn 7 6 9 2 (set (reg:DI 80 [ u8.0_1 ])
(zero_extend:DI*(mem/v/c*:QI (symbol_ref:DI ("*.LANCHOR0") [flags 0x182]) [0
u8D.2193+0 S1 A8]))) "volatile.c":5:11 459 {simple_load_uextdiqidi}
(nil))
test.c.302r.split1
(insn 27 6 28 2 (set (reg:DI 98)
(unspec:DI [
(symbol_ref:DI ("*.LANCHOR0") [flags 0x182])
] UNSPEC_PCALAU12I_GR)) "volatile.c":5:11 -1
(nil))
(insn 28 27 9 2 (set (reg:DI 80 [ u8.0_1 ])
(zero_extend:DI*(mem:*QI (lo_sum:DI (reg:DI 98)
(symbol_ref:DI ("*.LANCHOR0") [flags 0x182])) [0 S1 A8])))
"volatile.c":5:11 -1
(nil))
The volatile property of the mem here is gone, so the test fails.
