20faf78919
Thinlink provides an opportunity to propagate function attributes across modules, enabling additional propagation opportunities. This change propagates (currently default off, turn on with `disable-thinlto-funcattrs=1`) noRecurse and noUnwind based off of function summaries of the prevailing functions in bottom-up call-graph order. Testing on clang self-build: 1. There's a 35-40% increase in noUnwind functions due to the additional propagation opportunities. 2. Throughput is measured at 10-15% increase in thinlink time which itself is 1.5% of E2E link time. Implementation-wise this adds the following summary function attributes: 1. noUnwind: function is noUnwind 2. mayThrow: function contains a non-call instruction that `Instruction::mayThrow` returns true on (e.g. windows SEH instructions) 3. hasUnknownCall: function contains calls that don't make it into the summary call-graph thus should not be propagated from (e.g. indirect for now, could add no-opt functions as well) Testing: Clang self-build passes and 2nd stage build passes check-all ninja check-all with newly added tests passing Reviewed By: tejohnson Differential Revision: https://reviews.llvm.org/D36850
44 lines
1.9 KiB
LLVM
44 lines
1.9 KiB
LLVM
; REQUIRES: x86-registered-target
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; Test that FunctionAttr Propagation is generating correct summaries
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; RUN: split-file %s %t
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; RUN: opt -module-summary %t/a.ll -o %t/a.bc
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; RUN: opt -module-summary %t/b.ll -o %t/b.bc
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; RUN: llvm-lto2 run -disable-thinlto-funcattrs=0 %t/a.bc %t/b.bc -o %t1.o -save-temps \
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; RUN: -r=%t/a.bc,call_extern,plx \
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; RUN: -r=%t/a.bc,extern, \
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; RUN: -r=%t/b.bc,extern,p
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; RUN: llvm-dis %t1.o.index.bc -o - | FileCheck %s --check-prefix=CHECK-INDEX
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; RUN: llvm-dis %t1.o.1.1.promote.bc -o - | FileCheck %s --check-prefix=CHECK-IR
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;; Summary for call_extern. Note that llvm-lto2 writes out the index before propagation occurs so call_extern doesn't have its flags updated.
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; CHECK-INDEX: ^2 = gv: (guid: 13959900437860518209, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 1, canAutoHide: 0), insts: 2, calls: ((callee: ^3)))))
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;; Summary for extern
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; CHECK-INDEX: ^3 = gv: (guid: 14959766916849974397, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 1, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 1, mayThrow: 0, hasUnknownCall: 0))))
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;--- a.ll
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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declare void @extern()
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; CHECK-IR: Function Attrs: norecurse nounwind
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; CHECK-IR-NEXT: define dso_local void @call_extern()
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define void @call_extern() {
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call void @extern()
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ret void
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}
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;--- b.ll
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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attributes #0 = { nounwind norecurse }
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define void @extern() #0 {
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ret void
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}
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