http://llvm.org/bugs/show_bug.cgi?id=21115
Bug ID: 21115
Summary: Performance regression caused by changes in machine
sink
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Common Code Generator Code
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected]
Classification: Unclassified
Created attachment 13108
--> http://llvm.org/bugs/attachment.cgi?id=13108&action=edit
Test
After changes in revision 216862 I see performance regression at least on x86
Silvermont on attached test case.
To reproduce compile it with:
llc -O2 -mcpu=slm test.ll
The reason of regression is machine sink doesn't move some add operations out
of loop:
Revision 216861:
addl %edx, %ebx
addl $1, %esi
addl %ebp, %ecx
cmpl $512, %ebx # imm = 0x200
jl .LBB0_5 <--- Back edge
# BB#6: # %for.cond4.for.end_crit_edge
# in Loop: Header=BB0_4 Depth=2
movl 20(%esp), %edx # 4-byte Reload
leal (%edx,%ecx), %edi <--- add moved out of loop
movl 16(%esp), %edx # 4-byte Reload
movl %edi, t_run_test.imagHi_1
leal (%edx,%ecx), %ebp <--- add moved out of loop
movl %esi, %edx
movl %eax, %esi
movl 12(%esp), %eax # 4-byte Reload
movl %ebp, t_run_test.realHi_1
addl %ecx, %eax <--- add moved out of loop
addl 8(%esp), %ecx # 4-byte Folded Reload <--- add moved out
of loop
movl %eax, t_run_test.imagLow_1
movl %esi, %eax
movl %edx, %esi
movl 4(%esp), %edx # 4-byte Reload
movl %ecx, t_run_test.realLow_1
Revision 21862:
cmpl $512, %ecx # imm = 0x200
leal (%eax,%ebx), %ebp <--- add inside loop
movl 24(%esp), %eax # 4-byte Reload
leal (%edx,%ebx), %edx <--- add inside loop
leal (%edi,%ebx), %edi <--- add inside loop
leal (%eax,%ebx), %eax <--- add inside loop
jl .LBB0_5 <--- Back edge
# BB#6: # %for.cond4.for.end_crit_edge
# in Loop: Header=BB0_4 Depth=2
movl %edi, t_run_test.realLow_1
movl %edx, t_run_test.imagLow_1
movl %eax, t_run_test.realHi_1
movl %ebp, t_run_test.imagHi_1
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