3e05ab6322
Currently for thin-lto, the imported static global values (functions, variables, etc) will be promoted/renamed from e.g., foo() to foo.llvm.(). Such a renaming caused difficulties in live patching since function name is changed ([1]). It is possible that some global value names have to be promoted to avoid name collision and linker failure. But in practice, majority of name promotions can be avoided. In [2], the suggestion is that thin-lto pre-link decides whether a particular global value needs name promotion or not. If yes, later on in thinBackend() the name will be promoted. I compiled a particular linux kernel version (latest bpf-next tree) and found 1216 global values with suffix .llvm.. With this patch, the number of promoted functions is 2, 98% reduction from the original kernel build. If some native objects are not participating with LTO, name promotions have to be done to avoid potential linker issues. So the current implementation cannot be on by default. But in certain cases, e.g., linux kernel build, people can enable lld flag --lto-whole-program-visibility to reduce the number of functions like foo.llvm.(). For ThinLTOCodeGenerator.cpp which is used by llvm-lto tool and a few other rare cases, reducing the number of renaming due to promotion, is not implemented as lld flag '-lto-whole-program-visibility' is not supported in ThinLTOCodeGenerator.cpp for now. In summary, this pull request only supports llvm-lto2 style workflow. The feature is off by default. To enable the future, lld flag '-lto-whole-program-visibility' and llvm flag '-always-rename-promoted-locals=false' are needed. The link [3] has more context for the pull request discussions. [1] https://lpc.events/event/19/contributions/2212 [2] https://discourse.llvm.org/t/rfc-avoid-functions-like-foo-llvm-for-kernel-live-patch/89400 [3] https://github.com/llvm/llvm-project/pull/178587
166 lines
8.2 KiB
LLVM
166 lines
8.2 KiB
LLVM
; Test to check both the callgraph and refgraph in summary
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; RUN: opt -module-summary %s -o %t.o
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; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
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; RUN: llvm-dis -o - %t.o | FileCheck %s --check-prefix=DIS
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; Round trip it through llvm-as
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; RUN: llvm-dis -o - %t.o | llvm-as -o - | llvm-dis -o - | FileCheck %s --check-prefix=DIS
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; CHECK: <SOURCE_FILENAME
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; "bar"
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; CHECK-NEXT: <GLOBALVAR {{.*}} op0=0 op1=3
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; "globalvar"
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; CHECK-NEXT: <GLOBALVAR {{.*}} op0=3 op1=9
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; "func"
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; CHECK-NEXT: <FUNCTION op0=12 op1=4
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; "func2"
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; CHECK-NEXT: <FUNCTION op0=16 op1=5
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; "foo"
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; CHECK-NEXT: <FUNCTION op0=21 op1=3
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; "func3"
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; CHECK-NEXT: <FUNCTION op0=24 op1=5
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; "W"
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; CHECK-NEXT: <FUNCTION op0=29 op1=1
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; "X"
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; CHECK-NEXT: <FUNCTION op0=30 op1=1
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; "Y"
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; CHECK-NEXT: <FUNCTION op0=31 op1=1
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; "Z"
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; CHECK-NEXT: <FUNCTION op0=32 op1=1
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; "llvm.ctpop.i8"
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; CHECK-NEXT: <FUNCTION op0=33 op1=13
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; "main"
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; CHECK-NEXT: <FUNCTION op0=46 op1=4
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; See if the calls and other references are recorded properly using the
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; expected value id and other information as appropriate (callsite cout
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; for calls). Use different linkage types for the various test cases to
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; distinguish the test cases here (op1 contains the linkage type).
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; Note that op3 contains the # non-call references.
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; This also ensures that we didn't include a call or reference to intrinsic
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; llvm.ctpop.i8.
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; CHECK: <GLOBALVAL_SUMMARY_BLOCK
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; Function main contains call to func, as well as address reference to func:
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; op0=main op4=func op5=func
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; CHECK-DAG: <PERMODULE_PROFILE {{.*}} op0=11 op1=0 {{.*}} op4=1 op5=0 op6=0 op7=2 op8=2 op9=0/>
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; Function W contains a tail call to func3 as well as a reference to globalvar:
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; op0=W op4=globalvar op5=func3
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; CHECK-DAG: <PERMODULE_PROFILE {{.*}} op0=6 op1=5 {{.*}} op4=1 op5=0 op6=0 op7=1 op8=5 op9=8/>
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; Function X contains call to foo, as well as address reference to foo
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; which is in the same instruction as the call:
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; op0=X op4=foo op5=foo
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; CHECK-DAG: <PERMODULE_PROFILE {{.*}} op0=7 op1=1 {{.*}} op4=1 op5=0 op6=0 op7=4 op8=4 op9=0/>
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; Function Y contains tail call to func2, and ensures we don't incorrectly add
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; a reference to it when reached while earlier analyzing the phi using its
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; return value:
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; op0=Y op4=func2
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; CHECK-DAG: <PERMODULE_PROFILE {{.*}} op0=8 op1=72 {{.*}} op4=0 op5=0 op6=0 op7=3 op8=8/>
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; Function Z contains a tail call to func2, and ensures we don't incorrectly add
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; a reference to it when reached while analyzing subsequent use of its return
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; value:
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; op0=Z op4=func2
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; CHECK-DAG: <PERMODULE_PROFILE {{.*}} op0=9 op1=3 {{.*}} op4=0 op5=0 op6=0 op7=3 op8=8/>
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; Variable bar initialization contains address reference to func:
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; op0=bar op2=func
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; CHECK-DAG: <PERMODULE_GLOBALVAR_INIT_REFS {{.*}} op0=0 op1=0 op2=3 op3=2/>
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; CHECK: </GLOBALVAL_SUMMARY_BLOCK>
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; CHECK: <STRTAB_BLOCK
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; CHECK-NEXT: blob data = 'barglobalvarfuncfunc2foofunc3WXYZllvm.ctpop.i8main{{.*}}'
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; ModuleID = 'thinlto-function-summary-refgraph.ll'
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@bar = global void (...)* bitcast (void ()* @func to void (...)*), align 8
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@globalvar = constant i32 0, align 4
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declare void @func() #0
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declare i32 @func2(...) #1
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declare void @foo(i8* %F) #0
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declare i32 @func3(i32* dereferenceable(4)) #2
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; Function Attrs: nounwind uwtable
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define weak_odr void @W() #0 {
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entry:
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%call = tail call i32 @func3(i32* nonnull dereferenceable(4) @globalvar)
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ret void
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}
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; Function Attrs: nounwind uwtable
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define available_externally void @X() #0 {
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entry:
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call void @foo(i8* bitcast (void (i8*)* @foo to i8*))
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ret void
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}
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; Function Attrs: nounwind uwtable
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define private i32 @Y(i32 %i) #0 {
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entry:
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%cmp3 = icmp slt i32 %i, 10
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br i1 %cmp3, label %while.body.preheader, label %while.end
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while.body.preheader: ; preds = %entry
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br label %while.body
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while.body: ; preds = %while.body.preheader, %while.body
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%j.05 = phi i32 [ %add, %while.body ], [ 0, %while.body.preheader ]
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%i.addr.04 = phi i32 [ %inc, %while.body ], [ %i, %while.body.preheader ]
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%inc = add nsw i32 %i.addr.04, 1
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%call = tail call i32 (...) @func2() #2
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%add = add nsw i32 %call, %j.05
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%exitcond = icmp eq i32 %inc, 10
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br i1 %exitcond, label %while.end.loopexit, label %while.body
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while.end.loopexit: ; preds = %while.body
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%add.lcssa = phi i32 [ %add, %while.body ]
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br label %while.end
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while.end: ; preds = %while.end.loopexit, %entry
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%j.0.lcssa = phi i32 [ 0, %entry ], [ %add.lcssa, %while.end.loopexit ]
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ret i32 %j.0.lcssa
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}
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; Function Attrs: nounwind uwtable
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define linkonce_odr i32 @Z() #0 {
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entry:
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%call = tail call i32 (...) @func2() #2
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ret i32 %call
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}
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declare i8 @llvm.ctpop.i8(i8)
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; Function Attrs: nounwind uwtable
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define i32 @main() #0 {
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entry:
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%retval = alloca i32, align 4
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%foo = alloca void (...)*, align 8
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store i32 0, i32* %retval, align 4
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store void (...)* bitcast (void ()* @func to void (...)*), void (...)** %foo, align 8
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%0 = load void (...)*, void (...)** %foo, align 8
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call void (...) %0()
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call void @func()
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call i8 @llvm.ctpop.i8( i8 10 )
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ret i32 0
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}
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; Don't try to match summary IDs. The numbering depends on the map iteration
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; order, which depends on GUID, and the private function Y GUID will depend
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; on the path to the test.
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; DIS: ^0 = module: (path: "{{.*}}", hash: (0, 0, 0, 0, 0))
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; DIS-DAG: = gv: (name: "Z", summaries: (function: (module: ^0, flags: (linkage: linkonce_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 2, calls: ((callee: ^{{.*}}, tail: 1))))) ; guid = 104084381700047393
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; DIS-DAG: = gv: (name: "X", summaries: (function: (module: ^0, flags: (linkage: available_externally, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 2, calls: ((callee: ^{{.*}})), refs: (^{{.*}})))) ; guid = 1881667236089500162
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; DIS-DAG: = gv: (name: "W", summaries: (function: (module: ^0, flags: (linkage: weak_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 2, calls: ((callee: ^{{.*}}, tail: 1)), refs: (^{{.*}})))) ; guid = 5790125716599269729
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; DIS-DAG: = gv: (name: "foo") ; guid = 6699318081062747564
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; DIS-DAG: = gv: (name: "func") ; guid = 7289175272376759421
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; DIS-DAG: = gv: (name: "func3") ; guid = 11517462787082255043
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; Check that default value of writeonly attribute is zero for constant variables
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; DIS-DAG: = gv: (name: "globalvar", summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 1, writeonly: 0, constant: 1)))) ; guid = 12887606300320728018
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; DIS-DAG: = gv: (name: "func2") ; guid = 14069196320850861797
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; DIS-DAG: = gv: (name: "llvm.ctpop.i8") ; guid = 15254915475081819833
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; DIS-DAG: = gv: (name: "main", summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 9, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 0, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 1, mustBeUnreachable: 0), calls: ((callee: ^{{.*}})), refs: (^{{.*}})))) ; guid = 15822663052811949562
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; DIS-DAG: = gv: (name: "bar", summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 1, writeonly: 1, constant: 0), refs: (^{{.*}})))) ; guid = 16434608426314478903
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; Don't try to match the exact GUID. Since it is private, the file path
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; will get hashed, and that will be test dependent.
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; DIS-DAG: = gv: (name: "Y", summaries: (function: (module: ^0, flags: (linkage: private, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 14, calls: ((callee: ^{{.*}}, tail: 1))))) ; guid =
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