[lld] [lld][ELF] Extend profile guided function ordering to ELF binaries (PR #117514)

[Ellis Hoag via llvm-commits]

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@@ -0,0 +1,269 @@
+# REQUIRES: aarch64
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+# RUN: llvm-mc -filetype=obj -triple=aarch64 a.s -o a.o
+# RUN: llvm-profdata merge a.proftext -o a.profdata
+# RUN: ld.lld -e main -o a.out a.o --irpgo-profile=a.profdata --bp-startup-sort=function --verbose-bp-section-orderer 2>&1 | FileCheck %s --check-prefix=STARTUP
+# RUN: ld.lld -e main -o a.out a.o --irpgo-profile=a.profdata --bp-startup-sort=function --verbose-bp-section-orderer --icf=all --bp-compression-sort=none 2>&1 | FileCheck %s --check-prefix=STARTUP
+
+# STARTUP: Ordered 3 sections using balanced partitioning
+
+# RUN: ld.lld -e main -o - a.o --irpgo-profile=a.profdata --bp-startup-sort=function --symbol-ordering-file a.orderfile | llvm-nm --numeric-sort --format=just-symbols - | FileCheck %s --check-prefix=ORDERFILE
+
+# ORDERFILE: _Z1Av
+# ORDERFILE: _Z1Fi
+# ORDERFILE: _Z1Ei
+# ORDERFILE: _Z1Di
+# ORDERFILE: _Z1Ci
+# ORDERFILE: _Z1Bi
+# ORDERFILE: main
+# ORDERFILE: r1
+# ORDERFILE: r2
----------------
ellishg wrote:

We only guarantee the order of the first few symbols because of the orderfile. Also, it would be good to add some data symbols to the orderfile. See my Mach-O test.
https://github.com/llvm/llvm-project/blob/d300337e93da4ed96b044557e4b0a30001967cf0/lld/test/MachO/bp-section-orderer.s#L21-L37

```suggestion
# ORDERFILE-DAG: _Z1Ci
# ORDERFILE-DAG: _Z1Bi
# ORDERFILE-DAG: main
# ORDERFILE-DAG: r1
# ORDERFILE-DAG: r2
```

https://github.com/llvm/llvm-project/pull/117514