[llvm] [ThinLTO] Allow importing based on a workload definition (PR #74545)

[Mircea Trofin via llvm-commits]

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+; RUN: mkdir -p %t_baseline
+; RUN: opt -module-summary %S/Inputs/workload1.ll -o %t_baseline/workload1.bc
+; RUN: opt -module-summary %S/Inputs/workload2.ll -o %t_baseline/workload2.bc
+; RUN: opt -module-summary %S/Inputs/workload3.ll -o %t_baseline/workload3.bc
+;
+; Normal run. The first module shouldn't get m2_f1
+;
+; RUN: llvm-lto2 run %t_baseline/workload1.bc %t_baseline/workload2.bc %t_baseline/workload3.bc \
+; RUN:  -o %t_baseline/result.o -save-temps \
+; RUN:  -r %t_baseline/workload1.bc,m1_f1,plx \
+; RUN:  -r %t_baseline/workload1.bc,interposable_f \
+; RUN:  -r %t_baseline/workload1.bc,noninterposable_f \
+; RUN:  -r %t_baseline/workload1.bc,m1_variant \
+; RUN:  -r %t_baseline/workload2.bc,m2_f1,plx \
+; RUN:  -r %t_baseline/workload2.bc,m2_f1_alias \
+; RUN:  -r %t_baseline/workload2.bc,interposable_f,p \
+; RUN:  -r %t_baseline/workload2.bc,noninterposable_f,p \
+; RUN:  -r %t_baseline/workload2.bc,m2_variant \
+; RUN:  -r %t_baseline/workload3.bc,m1_f1 \
+; RUN:  -r %t_baseline/workload3.bc,m3_f1,plx
+; RUN: llvm-dis %t_baseline/result.o.1.3.import.bc -o - | FileCheck %s --check-prefix=NOPROF
+;
+; NOPROF-NOT: m2_f1
+;
+; The run with workload definitions - same other options.
+;
+; RUN: mkdir -p %t
+; RUN: opt -module-summary %S/Inputs/workload1.ll -o %t/workload1.bc
+; RUN: opt -module-summary %S/Inputs/workload2.ll -o %t/workload2.bc
+; RUN: opt -module-summary %S/Inputs/workload3.ll -o %t/workload3.bc
+; RUN: echo '{"m1_f1":["m2_f1", "m2_f1_alias", "interposable_f", "noninterposable_f"], \
+; RUN:  "m2_f1":["m1_f1", "m1_f2"]}' > %t/workload_defs.json
+; RUN: llvm-lto2 run %t/workload1.bc %t/workload2.bc %t/workload3.bc \
+; RUN:  -thinlto-workload-def=%t/workload_defs.json -o %t/result.o -save-temps \
+; RUN:  -r %t/workload1.bc,m1_f1,plx \
+; RUN:  -r %t/workload1.bc,interposable_f \
+; RUN:  -r %t/workload1.bc,noninterposable_f \
+; RUN:  -r %t/workload1.bc,m1_variant \
+; RUN:  -r %t/workload2.bc,m2_f1,plx \
+; RUN:  -r %t/workload2.bc,m2_f1_alias \
+; RUN:  -r %t/workload2.bc,interposable_f,p \
+; RUN:  -r %t/workload2.bc,noninterposable_f,p \
+; RUN:  -r %t/workload2.bc,m2_variant \
+; RUN:  -r %t/workload3.bc,m1_f1 \
+; RUN:  -r %t/workload3.bc,m3_f1,plx
+; RUN: llvm-dis %t/result.o.1.3.import.bc -o - | FileCheck %s --check-prefix=FIRST
+; RUN: llvm-dis %t/result.o.2.3.import.bc -o - | FileCheck %s --check-prefix=SECOND
+; RUN: llvm-dis %t/result.o.3.3.import.bc -o - | FileCheck %s --check-prefix=THIRD
+;
+; The third module is bitwse-identical to the "normal" run, as the 
+; RUN: diff %t_baseline/result.o.3.3.import.bc %t/result.o.3.3.import.bc
+;
+; This time, we expect m1 to have m2_f1 and the m2 variant of interposable_f,
+; while keeping its variant of noninterposable_f
+;
+; FIRST-LABEL: @m1_f1
+; FIRST-LABEL: @m1_f2
+; FIRST-LABEL: define available_externally void @noninterposable_f
+; FIRST-NEXT: call void @m1_variant
+; FIRST-LABEL: @m2_f1
+; FIRST-LABEL: define available_externally void @interposable_f
+; FIRST-NEXT: call void @m2_variant
+; FIRST-NOT:   @m2_f1_alias
----------------
mtrofin wrote:

It should be actually. (summarizing offline discussion): We need to assume aliases and aliasees are given in the import list because the source of the workload def may be a tool working off sections in the binary, and there's no information as to which name is alias or aliasee - all we know is that multiple symbols map to the same address. That aside, we will then import what's given in the list. Today, that will mean that if a function and its alias are imported, the alias will be instantiated as a clone of the original. That's likely rare; anyway, it can be addressed subsequently (i.e. have a mode that, instead of cloning, replaces callsites)

https://github.com/llvm/llvm-project/pull/74545