4609f60ebc
It seems the earlier implementation does not follow the description in LoopRotationPass.h: It rotates loops even if they are already laid out correctly. The diff adjusts the behaviour. Given that the impact of LoopInversionPass is minor, this change won't yield significant perf differences. Tested on clang-10: there seems to be a 0.1%-0.3% cpu win and a small reduction of branch misses. **Before:** BOLT-INFO: 120 Functions were reordered by LoopInversionPass **After:** BOLT-INFO: 79 Functions were reordered by LoopInversionPass Reviewed By: yota9 Differential Revision: https://reviews.llvm.org/D121921
48 lines
1.5 KiB
ArmAsm
48 lines
1.5 KiB
ArmAsm
# REQUIRES: system-linux
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# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \
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# RUN: %s -o %t.o
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# RUN: link_fdata %s %t.o %t.fdata
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# RUN: link_fdata %s %t.o %t.fdata2 "FDATA2"
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# RUN: link_fdata %s %t.o %t.fdata3 "FDATA3"
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# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
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# RUN: llvm-bolt %t.exe -data %t.fdata -reorder-blocks=cache+ -print-finalized \
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# RUN: -loop-inversion-opt -o %t.out | FileCheck %s
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# RUN: llvm-bolt %t.exe -data %t.fdata2 -reorder-blocks=cache+ -print-finalized \
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# RUN: -loop-inversion-opt -o %t.out2 | FileCheck --check-prefix="CHECK2" %s
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# RUN: llvm-bolt %t.exe -data %t.fdata3 -reorder-blocks=none -print-finalized \
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# RUN: -loop-inversion-opt -o %t.out3 | FileCheck --check-prefix="CHECK3" %s
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# The case where the loop is used:
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# FDATA: 1 main 2 1 main #.J1# 0 420
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# FDATA: 1 main b 1 main #.Jloop# 0 420
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# FDATA: 1 main b 1 main d 0 1
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# CHECK: BB Layout : .LBB00, .Ltmp0, .Ltmp1, .LFT0
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# The case where the loop is unused:
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# FDATA2: 1 main 2 1 main #.J1# 0 420
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# FDATA2: 1 main b 1 main #.Jloop# 0 1
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# FDATA2: 1 main b 1 main d 0 420
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# CHECK2: BB Layout : .LBB00, .Ltmp1, .LFT0, .Ltmp0
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# The case where the loop does not require rotation:
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# FDATA3: 1 main 2 1 main #.J1# 0 420
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# FDATA3: 1 main b 1 main #.Jloop# 0 420
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# FDATA3: 1 main b 1 main d 0 1
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# CHECK3: BB Layout : .LBB00, .Ltmp0, .Ltmp1, .LFT0
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.text
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.globl main
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.type main, %function
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.size main, .Lend-main
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main:
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xor %eax, %eax
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jmp .J1
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.Jloop:
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inc %rax
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.J1:
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cmp $16, %rax
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jl .Jloop
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retq
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.Lend:
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