Hi,all
Can gatekeep help review this bug? It is a SL specifial bug, however, we
plan to check the patch into open64 repository and it is general since other
targets may also meet it if they do op substitutions.
The cut-down bug case is:
extern void* memcpy(void *, const void *, unsigned int);
etern unsigned int TRC_ITOA(unsigned int, unsigned char *, unsigned int);
void test_f(unsigned int num, unsigned char *buf, unsigned int len) {
unsigned int str_len = 0;
unsigned char tmp_buf[len+1];
str_len = TRC_ITOA(num, tmp_buf, 10);
memcpy(buf + len - str_len, tmp_buf, str_len);
}
SL features 16bit insns substitution for those frequently used 32bit
risc insns. however, for this case, it will generate wrong code. SL5, our
single issue processor will generate the following epilog BB code:
.LBB3_test_f:
.loc 1 11 0
# 11 }
ldw $24,-24($30) # [0] gra_spill1
mv16 $sp,$30 # [1]
mvtc16 ra,$24 # [2]
ldw $7,-28($30) # [3] gra_spill2
mv16 $30,$7 # [5]
ret16 # [6]
$sp is restored by $bp($30) before fetching the spilled $30 back. when
interrupt happens, the stack is clobbered and then $30.
This bug is caused by the substiton on the $sp adjust insn and forget
to annotate it,
so the scheduler could not find the sp adjust insn in the exit BB and
it do aggressive scheduling.
We suggest a patch for this bug:
Index: osprey/be/cg/SL/disp_instr.cxx
===================================================================
--- osprey/be/cg/SL/disp_instr.cxx (revision 3461)
+++ osprey/be/cg/SL/disp_instr.cxx (working copy)
@@ -123,6 +123,14 @@
Copy_WN_For_Memory_OP(newop, _cur_op);
}
BB_Insert_Op_Before(OP_bb(_cur_op), _cur_op, newop);
+
+ if (_cur_op == BB_entry_sp_adj_op(_cur_op->bb)) {
+ Set_BB_entry_sp_adj_op(_cur_op->bb,newop);
+ }
+ if (_cur_op == BB_exit_sp_adj_op(_cur_op->bb)) {
+ Set_BB_exit_sp_adj_op(_cur_op->bb,newop);
+ }
+
OP_Change_To_Noop(_cur_op);
_cur_op = newop;
return;
after the patch, the sp adjust insn is not scheduled and the bug so fixed.
.LBB3_test_f:
.loc 1 11 0
# 11 }
ldw $24,-24($30) # [0] gra_spill1
ldw $7,-28($30) # [1] gra_spill2
mvtc16 ra,$24 # [2]
mv16 $sp,$30 # [3]
mv16 $30,$7 # [4]
ret16 # [5]
.end test_f
Cound gatekeep help review this?
Thanks
Gang
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