[lld][ELF] filter out section symbols when use BP reorder (#151685)
When using Temporal Profiling with the BP algorithm, we encounter an
issue with the internal function reorder. In cases where the symbol
table contains entries like:
```
Symbol table '.symtab' contains 45 entries:
Num: Value Size Type Bind Vis Ndx Name
10: 0000000000000000 0 SECTION LOCAL DEFAULT 18 .text.L1
11: 0000000000000000 24 FUNC LOCAL DEFAULT 18 L1
````
The zero-sized section symbol .text.L1 gets stored in the secToSym map
first. However, when the function lookup searches for L1 (as seen in
[BPSectionOrdererBase.inc:191](https://github.com/llvm/llvm-project/blob/main/lld/include/lld/Common/BPSectionOrdererBase.inc#L191)),
it fails to find the correct entry in rootSymbolToSectionIdxs because
the section symbol has already claimed that slot.
This patch fixes the issue by skipping zero-sized symbols during the
addSections process, ensuring that function symbols are properly
registered for lookup.
This commit is contained in:
Pengying Xu
GitHub
parent
b9ca01b746
commit
ffdaf85a95
@ -76,10 +76,12 @@ DenseMap<const InputSectionBase *, int> elf::runBalancedPartitioning(
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if (!d)
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return;
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auto *sec = dyn_cast_or_null<InputSection>(d->section);
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// Skip empty, discarded, ICF folded sections, .bss. Skipping ICF folded
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// sections reduces duplicate detection work in BPSectionOrderer.
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if (!sec || sec->size == 0 || !sec->isLive() || sec->repl != sec ||
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!sec->content().data() || !orderer.secToSym.try_emplace(sec, d).second)
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// Skip section symbols. Skip empty, discarded, ICF folded sections, .bss.
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// Skipping ICF folded sections reduces duplicate detection work in
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// BPSectionOrderer.
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if (sym.isSection() || !sec || sec->size == 0 || !sec->isLive() ||
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sec->repl != sec || !sec->content().data() ||
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!orderer.secToSym.try_emplace(sec, d).second)
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return;
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rootSymbolToSectionIdxs[CachedHashStringRef(
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lld::utils::getRootSymbol(sym.getName()))]
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@ -21,38 +21,38 @@
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# RUN: llvm-profdata merge a.proftext -o a.profdata
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# RUN: ld.lld a.o --irpgo-profile=a.profdata --bp-startup-sort=function --verbose-bp-section-orderer --icf=all --gc-sections 2>&1 | FileCheck %s --check-prefix=STARTUP-FUNC-ORDER
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# STARTUP-FUNC-ORDER: Ordered 3 sections ([[#]] bytes) using balanced partitioning
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# STARTUP-FUNC-ORDER: Total area under the page fault curve: 3.
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# STARTUP-FUNC-ORDER: Ordered 4 sections ([[#]] bytes) using balanced partitioning
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# STARTUP-FUNC-ORDER: Total area under the page fault curve: 4.
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# RUN: ld.lld -o out.s a.o --irpgo-profile=a.profdata --bp-startup-sort=function
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# RUN: llvm-nm -jn out.s | tr '\n' , | FileCheck %s --check-prefix=STARTUP
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# STARTUP: s5,s4,s3,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d3,d2,d1,g1,{{$}}
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# STARTUP: s5,s4,s3,s2,s1,A,B,C,L1,F,E,D,merged1,merged2,G,_start,d4,d3,d2,d1,g1,{{$}}
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# RUN: ld.lld -o out.os a.o --irpgo-profile=a.profdata --bp-startup-sort=function --symbol-ordering-file a.txt
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# RUN: llvm-nm -jn out.os | tr '\n' , | FileCheck %s --check-prefix=ORDER-STARTUP
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# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,merged1,merged2,_start,d3,d2,d4,d1,g1,{{$}}
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# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,L1,merged1,merged2,G,_start,d3,d2,d4,d1,g1,{{$}}
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# RUN: ld.lld -o out.cf a.o --verbose-bp-section-orderer --bp-compression-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-FUNC
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# RUN: ld.lld -o out.cf.icf a.o --verbose-bp-section-orderer --bp-compression-sort=function --icf=all --gc-sections 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-ICF-FUNC
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# RUN: llvm-nm -jn out.cf | tr '\n' , | FileCheck %s --check-prefix=CFUNC
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# CFUNC: s5,s4,s3,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d3,d2,d1,g1,{{$}}
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# CFUNC: s5,s4,s3,s2,s1,C,E,D,B,G,F,merged1,merged2,A,_start,L1,d4,d3,d2,d1,g1,{{$}}
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# RUN: ld.lld -o out.cd a.o --verbose-bp-section-orderer --bp-compression-sort=data 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-DATA
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# RUN: llvm-nm -jn out.cd | tr '\n' , | FileCheck %s --check-prefix=CDATA
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# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}
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# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,L1,G,_start,d4,d1,d3,d2,g1,{{$}}
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# RUN: ld.lld -o out.cb a.o --verbose-bp-section-orderer --bp-compression-sort=both 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
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# RUN: llvm-nm -jn out.cb | tr '\n' , | FileCheck %s --check-prefix=CBOTH
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# CBOTH: s5,s3,s4,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d1,d3,d2,g1,{{$}}
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# CBOTH: s5,s3,s4,s2,s1,C,E,D,B,G,F,merged1,merged2,A,_start,L1,d4,d1,d3,d2,g1,{{$}}
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# RUN: ld.lld -o out.cbs a.o --verbose-bp-section-orderer --bp-compression-sort=both --irpgo-profile=a.profdata --bp-startup-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
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# RUN: llvm-nm -jn out.cbs | tr '\n' , | FileCheck %s --check-prefix=CBOTH-STARTUP
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# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}
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# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,L1,F,E,D,merged1,merged2,G,_start,d4,d1,d3,d2,g1,{{$}}
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# BP-COMPRESSION-FUNC: Ordered 9 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-ICF-FUNC: Ordered 8 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-FUNC: Ordered 11 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-ICF-FUNC: Ordered 9 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-DATA: Ordered 9 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-BOTH: Ordered 18 sections ([[#]] bytes) using balanced partitioning
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# BP-COMPRESSION-BOTH: Ordered 20 sections ([[#]] bytes) using balanced partitioning
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#--- a.proftext
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:ir
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@ -63,7 +63,7 @@
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1
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# Weight
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1
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A, B, C
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A, B, C, L1
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A
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# Func Hash:
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@ -97,6 +97,14 @@ D
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# Counter Values:
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1
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L1
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# Func Hash:
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5555
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# Num Counters:
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1
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# Counter Values:
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1
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#--- a.txt
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A
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F
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@ -137,6 +145,9 @@ void A() {}
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RETAIN int merged1(int a) { return F(a + 101); }
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int merged2(int a) { return F(a + 101); }
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RETAIN static int L1(int a) { return a + 103; }
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int G(int a) { return L1(a); }
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int _start() { return 0; }
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#--- gen
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@ -148,7 +159,7 @@ clang --target=aarch64-linux-gnu -O0 -ffunction-sections -fdata-sections -fno-as
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.p2align 2
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.type F,@function
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F: // @F
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -167,7 +178,7 @@ F: // @F
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.p2align 2
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.type C,@function
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C: // @C
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -186,7 +197,7 @@ C: // @C
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.p2align 2
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.type E,@function
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E: // @E
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -205,7 +216,7 @@ E: // @E
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.p2align 2
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.type D,@function
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D: // @D
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -224,7 +235,7 @@ D: // @D
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.p2align 2
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.type B,@function
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B: // @B
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -243,7 +254,7 @@ B: // @B
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.p2align 2
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.type A,@function
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A: // @A
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// %bb.0: // %entry
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// %bb.0:
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ret
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.Lfunc_end5:
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.size A, .Lfunc_end5-A
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@ -253,7 +264,7 @@ A: // @A
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.p2align 2
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.type merged1,@function
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merged1: // @merged1
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -272,7 +283,7 @@ merged1: // @merged1
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.p2align 2
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.type merged2,@function
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merged2: // @merged2
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// %bb.0: // %entry
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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@ -286,16 +297,48 @@ merged2: // @merged2
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.Lfunc_end7:
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.size merged2, .Lfunc_end7-merged2
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// -- End function
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.section .text.L1,"axR",@progbits
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.p2align 2 // -- Begin function L1
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.type L1,@function
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L1: // @L1
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// %bb.0:
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sub sp, sp, #16
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str w0, [sp, #12]
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ldr w8, [sp, #12]
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add w0, w8, #103
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add sp, sp, #16
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ret
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.Lfunc_end8:
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.size L1, .Lfunc_end8-L1
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// -- End function
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.section .text.G,"ax",@progbits
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.globl G // -- Begin function G
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.p2align 2
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.type G,@function
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G: // @G
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// %bb.0:
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sub sp, sp, #32
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stp x29, x30, [sp, #16] // 16-byte Folded Spill
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add x29, sp, #16
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stur w0, [x29, #-4]
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ldur w0, [x29, #-4]
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bl L1
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ldp x29, x30, [sp, #16] // 16-byte Folded Reload
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add sp, sp, #32
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ret
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.Lfunc_end9:
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.size G, .Lfunc_end9-G
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// -- End function
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.section .text._start,"ax",@progbits
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.globl _start // -- Begin function _start
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.p2align 2
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.type _start,@function
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_start: // @_start
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// %bb.0: // %entry
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// %bb.0:
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mov w0, wzr
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ret
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.Lfunc_end8:
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.size _start, .Lfunc_end8-_start
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.Lfunc_end10:
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.size _start, .Lfunc_end10-_start
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// -- End function
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.type s5,@object // @s5
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.section .rodata.s5,"a",@progbits
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@ -395,3 +438,4 @@ g1:
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.addrsig_sym B
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.addrsig_sym A
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.addrsig_sym merged1
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.addrsig_sym L1
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