https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64479
Bug ID: 64479
Summary: wrong optimization delayed-branch for SH
Product: gcc
Version: 4.8.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: oshima...@yagoto-urayama.jp
On NetBSD/landisk(sh3) 7.0_BETA, gcc4.8.4 generates some strange code.
Test case:
int foo(int);
void bar(int *);
void func(int args)
{
int key;
int flag = (args==0);
bar(&key);
if (!args) foo(1);
if (foo(args)) {
if (flag && key == 0) foo(2);
else
if (flag) foo(3);
}
}
it generated by compile with -Os -S:
func:
.LFB0:
.cfi_startproc
mov.l r8,@-r15
.cfi_def_cfa_offset 4
.cfi_offset 8, -4
mov.l r9,@-r15
.cfi_def_cfa_offset 8
.cfi_offset 9, -8
mov.l r10,@-r15
.cfi_def_cfa_offset 12
.cfi_offset 10, -12
mov.l r11,@-r15
.cfi_def_cfa_offset 16
.cfi_offset 11, -16
sts.l pr,@-r15
.cfi_def_cfa_offset 20
.cfi_offset 17, -20
add #-4,r15
.cfi_def_cfa_offset 24
mov.l .L16,r1
tst r4,r4
movt r8 # T bit -> R8
mov r4,r9
jsr @r1 # subroutine call (bar)
mov r15,r4
mov.l .L18,r11
bf .L2 # what condition? (T bit == 0?)
jsr @r11
mov #1,r4
.L2
When compiled with -Os -fno-delayed-branch -S:
func:
.LFB0:
.cfi_startproc
mov.l r8,@-r15
.cfi_def_cfa_offset 4
.cfi_offset 8, -4
mov.l r9,@-r15
.cfi_def_cfa_offset 8
.cfi_offset 9, -8
mov.l r10,@-r15
.cfi_def_cfa_offset 12
.cfi_offset 10, -12
mov.l r11,@-r15
.cfi_def_cfa_offset 16
.cfi_offset 11, -16
sts.l pr,@-r15
.cfi_def_cfa_offset 20
.cfi_offset 17, -20
add #-4,r15
.cfi_def_cfa_offset 24
mov.l .L16,r1
tst r4,r4
movt r8 # T bit -> R8
mov r4,r9
mov r15,r4
jsr @r1 # subroutine call (bar)
nop
tst r8,r8 # if (R8 == 0) then T bit = 1
mov.l .L18,r11
bt .L2 # if (T bit == 1) branch .L2
mov #1,r4
jsr @r11
nop
.L2:
With -Os (include -fdelayed-branch), tst r8,r8 instruction is omitted, and
branch condition is inverted.
The same problem in this case occurs in flow_loops_find() function of
gcc/cfgloop.c when building gcc 4.8.4 for NetBSD/sh3-binary. So gcc
native-binary for sh3 will be wrong.
