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llvm-project/lld/test/ELF/lto/comdat-nodeduplicate.ll
Mingming Liu dda73336ad
[ThinLTO]Record import type in GlobalValueSummary::GVFlags (#87597) 
The motivating use case is to support import the function declaration
across modules to construct call graph edges for indirect calls [1]
when importing the function definition costs too much compile time
(e.g., the function is too large has no `noinline` attribute).
1. Currently, when the compiled IR module doesn't have a function
definition but its postlink combined summary contains the function
summary or a global alias summary with this function as aliasee, the
function definition will be imported from source module by IRMover. The
implementation is in FunctionImporter::importFunctions [2]
2. In order for FunctionImporter to import a declaration of a function,
both function summary and alias summary need to carry the def / decl
state. Specifically, all existing summary fields doesn't differ across
import modules, but the def / decl state of is decided by
`<ImportModule, Function>`.

This change encodes the def/decl state in `GlobalValueSummary::GVFlags`.

In the subsequent changes
1. The indexing step `computeImportForModule` [3]
will compute the set of definitions and the set of declarations for each
module, and passing on the information to bitcode writer.
2. Bitcode writer will look up the def/decl state and sets the state
when it writes out the flag value. This is demonstrated in
https://github.com/llvm/llvm-project/pull/87600
3. Function importer will read the def/decl state when reading the
combined summary to figure out two sets of global values, and IRMover
will be updated to import the declaration (aka linkGlobalValuePrototype [4])
into the destination module.

- The next change is https://github.com/llvm/llvm-project/pull/87600

[1] mentioned in rfc https://discourse.llvm.org/t/rfc-for-better-call-graph-sort-build-a-more-complete-call-graph-by-adding-more-indirect-call-edges/74029#support-cross-module-function-declaration-import-5
[2] 3b337242ee/llvm/lib/Transforms/IPO/FunctionImport.cpp (L1608-L1764)
[3] 3b337242ee/llvm/lib/Transforms/IPO/FunctionImport.cpp (L856)
[4] 3b337242ee/llvm/lib/Linker/IRMover.cpp (L605)
2024-04-10 19:46:01 -07:00

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; REQUIRES: x86, shell
;; Keep __profd_foo in a nodeduplicate comdat, despite a comdat of the same name
;; in a previous object file.
;; Regular LTO
; RUN: rm -rf %t && split-file %s %t
; RUN: llvm-as %t/a.ll -o %t/a.bc
; RUN: llvm-as %t/b.ll -o %t/b.bc
; RUN: llvm-as %t/c.ll -o %t/c.bc
; RUN: ld.lld --save-temps -u foo %t/a.bc --start-lib %t/b.bc --end-lib -o %t/ab
; RUN: FileCheck %s --check-prefix=RESOL_AB < %t/ab.resolution.txt
; RUN: llvm-readelf -x .data %t/ab | FileCheck %s --check-prefix=DATA
; RESOL_AB: -r={{.*}}b.bc,__profc_foo,pl{{$}}
;; .data contains a.bc:data. b.bc:data and c.bc:data are discarded.
; DATA: 0x[[#%x,]] 01000000 00000000 ........
;; __profc_foo from c.bc is non-prevailing and thus discarded.
; RUN: ld.lld --save-temps -u foo -u c %t/a.bc --start-lib %t/b.bc %t/c.bc --end-lib -o %t/abc
; RUN: FileCheck %s --check-prefix=RESOL_ABC < %t/abc.resolution.txt
; RUN: llvm-readelf -x .data %t/abc | FileCheck %s --check-prefix=DATA
; RESOL_ABC: -r={{.*}}b.bc,__profc_foo,pl{{$}}
; RESOL_ABC: -r={{.*}}c.bc,__profc_foo,{{$}}
;; ThinLTO
; RUN: rm -rf %t && split-file %s %t
; RUN: opt --module-summary %t/a.ll -o %t/a.bc
; RUN: opt --module-summary %t/b.ll -o %t/b.bc
; RUN: opt --module-summary %t/c.ll -o %t/c.bc
; RUN: ld.lld --thinlto-index-only --save-temps -u foo %t/a.bc %t/b.bc -o %t/ab
; RUN: FileCheck %s --check-prefix=RESOL_AB < %t/ab.resolution.txt
; RUN: (llvm-dis < %t/b.bc && llvm-dis < %t/b.bc.thinlto.bc) | FileCheck %s --check-prefix=IR_AB
; RUN: ld.lld -u foo %t/a.bc %t/b.bc -o %t/ab
; RUN: llvm-readelf -x .data %t/ab | FileCheck %s --check-prefix=DATA
; RUN: ld.lld --thinlto-index-only --save-temps -u foo %t/a.bc --start-lib %t/b.bc --end-lib -o %t/ab
; RUN: FileCheck %s --check-prefix=RESOL_AB < %t/ab.resolution.txt
; RUN: (llvm-dis < %t/b.bc && llvm-dis < %t/b.bc.thinlto.bc) | FileCheck %s --check-prefix=IR_AB
; RUN: ld.lld -u foo %t/a.bc --start-lib %t/b.bc --end-lib -o %t/ab
; RUN: llvm-readelf -x .data %t/ab | FileCheck %s --check-prefix=DATA
; RUN: ld.lld --thinlto-index-only --save-temps -u foo -u c %t/a.bc --start-lib %t/b.bc %t/c.bc --end-lib -o %t/abc
; RUN: FileCheck %s --check-prefix=RESOL_ABC < %t/abc.resolution.txt
; RUN: (llvm-dis < %t/b.bc && llvm-dis < %t/b.bc.thinlto.bc) | FileCheck %s --check-prefix=IR_ABC
; RUN: ld.lld -u foo %t/a.bc --start-lib %t/b.bc %t/c.bc --end-lib -o %t/abc
; RUN: llvm-readelf -x .data %t/abc | FileCheck %s --check-prefix=DATA
; IR_AB-DAG: gv: (name: "__profd_foo", {{.*}} guid = [[PROFD:[0-9]+]]
; IR_AB-DAG: gv: (name: "__profc_foo", {{.*}} guid = [[PROFC:[0-9]+]]
;; Check extra attributes. b.bc:__profc_foo is prevailing, so it can be internalized.
; IR_AB-DAG: gv: (guid: [[PROFD]], summaries: (variable: (module: ^0, flags: (linkage: private, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0),
; IR_AB-DAG: gv: (guid: [[PROFC]], summaries: (variable: (module: ^0, flags: (linkage: internal, visibility: hidden, notEligibleToImport: 0, live: 1, dsoLocal: 1, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0))))
; IR_ABC-DAG: gv: (name: "__profd_foo", {{.*}} guid = [[PROFD:[0-9]+]]
; IR_ABC-DAG: gv: (name: "__profc_foo", {{.*}} guid = [[PROFC:[0-9]+]]
;; b.bc:__profc_foo prevails c.bc:__profc_foo, so it is exported and therefore not internalized.
; IR_ABC-DAG: gv: (guid: [[PROFD]], summaries: (variable: (module: ^0, flags: (linkage: private, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0),
; IR_ABC-DAG: gv: (guid: [[PROFC]], summaries: (variable: (module: ^0, flags: (linkage: weak, visibility: hidden, notEligibleToImport: 0, live: 1, dsoLocal: 1, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0))))
;--- a.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
$__profc_foo = comdat nodeduplicate
@__profc_foo = private global i64 1, comdat, align 8
@__profd_foo = private global ptr @__profc_foo, comdat($__profc_foo), align 8
declare void @b()
define i64 @foo() {
%v = load i64, ptr @__profc_foo
%inc = add i64 1, %v
store i64 %inc, ptr @__profc_foo
ret i64 %inc
}
define void @_start() {
call void @b()
ret void
}
;--- b.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
$__profc_foo = comdat nodeduplicate
@__profc_foo = weak hidden global i64 2, comdat, align 8
@__profd_foo = private global ptr @__profc_foo, comdat($__profc_foo)
define weak i64 @foo() {
%v = load i64, ptr @__profc_foo
%inc = add i64 1, %v
store i64 %inc, ptr @__profc_foo
ret i64 %inc
}
define void @b() {
ret void
}
;--- c.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
$__profc_foo = comdat nodeduplicate
@__profc_foo = weak hidden global i64 3, comdat, align 8
@__profd_foo = private global ptr @__profc_foo, comdat($__profc_foo)
define weak i64 @foo() {
%v = load i64, ptr @__profc_foo
%inc = add i64 1, %v
store i64 %inc, ptr @__profc_foo
ret i64 %inc
}
define void @c() {
ret void
}
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