| Message ID | 000401d0152a$283c13e0$78b43ba0$@arm.com |
|---|---|
| State | New |
| Headers | show |
On 11 December 2014 at 10:06, Bin Cheng <bin.cheng@arm.com> wrote: > gcc/testsuite/ChangeLog > 2014-12-11 Bin Cheng <bin.cheng@arm.com> > > * gcc.target/aarch64/ldp_stp_2.c: Make test less vulnerable. > * gcc.target/aarch64/ldp_stp_3.c: Ditto. OK /Marcus
Index: gcc/testsuite/gcc.target/aarch64/ldp_stp_2.c =================================================================== --- gcc/testsuite/gcc.target/aarch64/ldp_stp_2.c (revision 218558) +++ gcc/testsuite/gcc.target/aarch64/ldp_stp_2.c (working copy) @@ -7,10 +7,8 @@ long long foo () { long long ll = 0; - ll += arr[0][1]; ll += arr[1][0]; ll += arr[1][1]; - ll += arr[2][0]; return ll; } Index: gcc/testsuite/gcc.target/aarch64/ldp_stp_3.c =================================================================== --- gcc/testsuite/gcc.target/aarch64/ldp_stp_3.c (revision 218558) +++ gcc/testsuite/gcc.target/aarch64/ldp_stp_3.c (working copy) @@ -7,10 +7,8 @@ unsigned long long foo () { unsigned long long ll = 0; - ll += arr[0][1]; ll += arr[1][0]; ll += arr[1][1]; - ll += arr[2][0]; return ll; }
Hi, Case gcc.target/aarch64/ldp_stp_3.c test fails on aarch64-none-elf. Instead of merging the loads into ldp it generates: foo: adrp x1, .LANCHOR0 add x1, x1, :lo12:.LANCHOR0 ldr w0, [x1, 4] ldr w3, [x1, 20] ldr w2, [x1, 32] ldr w1, [x1, 16] add x2, x3, x2 add x0, x0, x1 add x0, x2, x0 ret Once register allocation decides to load [x1, 16] into x1(w1) like below: 14: x0:DI = zero_extend([x1:DI+0x4]) 7: x3:DI = zero_extend([x1:DI+0x14]) 10: x2:DI = zero_extend([x1:DI+0x20]) 17: x1:DI = zero_extend([x1:DI+0x10]) Instructions 14/7/10 are anti-dependent on insn 17, bug sched_fusion orders ready list (14/7/10) in ascending order of address. As a result insn 10 intervenes between 7 and 17. This patch fixes this by making cases less vulnerable. One possible fix is to move sched_fusion after regrename, it does help a lot. I didn't do that because regrenamre is currently disabled. Tested on aarch64-elf. Is it OK? Thanks, bin gcc/testsuite/ChangeLog 2014-12-11 Bin Cheng <bin.cheng@arm.com> * gcc.target/aarch64/ldp_stp_2.c: Make test less vulnerable. * gcc.target/aarch64/ldp_stp_3.c: Ditto.