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[ThinLTO] Record calls to aliases

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Summary:
When there is a call to an alias in the same module, we were not
adding a call edge. So we could incorrectly think that the alias
was dead if it was inlined in that function, despite having a
reference imported elsewhere. This resulted in unsats at link time.

Add a call edge when the call is to an alias.

Reviewers: davide, mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25384

llvm-svn: 283664
This commit is contained in:
Teresa Johnson 2016-10-08 16:11:42 +00:00
parent eb65d72d9c
commit 897bab9b35
2 changed files with 40 additions and 1 deletions
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13
llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
View File

@ -101,15 +101,26 @@ static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
auto CS = ImmutableCallSite(&I);
if (!CS)
continue;
auto *CalledValue = CS.getCalledValue();
auto *CalledFunction = CS.getCalledFunction();
// Check if this is an alias to a function. If so, get the
// called aliasee for the checks below.
if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) {
assert(!CalledFunction && "Expected null called function in callsite for alias");
CalledFunction = dyn_cast<Function>(GA->getBaseObject());
}
// Check if this is a direct call to a known function.
if (CalledFunction) {
// Skip nameless and intrinsics.
if (!CalledFunction->hasName() || CalledFunction->isIntrinsic())
continue;
auto ScaledCount = BFI ? BFI->getBlockProfileCount(&BB) : None;
// Use the original CalledValue, in case it was an alias. We want
// to record the call edge to the alias in that case. Eventually
// an alias summary will be created to associate the alias and
// aliasee.
auto *CalleeId =
M.getValueSymbolTable().lookup(CalledFunction->getName());
M.getValueSymbolTable().lookup(CalledValue->getName());
auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
: CalleeInfo::HotnessType::Unknown;

28
llvm/test/Bitcode/thinlto-alias2.ll Normal file
View File

@ -0,0 +1,28 @@
; Test to check the callgraph for call to alias in module.
; RUN: opt -module-summary %s -o %t.o
; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
; CHECK: <GLOBALVAL_SUMMARY_BLOCK
; CHECK-NEXT: <VERSION
; CHECK-NEXT: <PERMODULE {{.*}} op3=0 op4=[[ALIASID:[0-9]+]]/>
; CHECK-NEXT: <PERMODULE {{.*}} op0=[[ALIASEEID:[0-9]+]]
; CHECK-NEXT: <ALIAS {{.*}} op0=[[ALIASID]] {{.*}} op2=[[ALIASEEID]]/>
; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
; ModuleID = 'thinlto-alias2.ll'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i32 @main() {
entry:
call void (...) @analias()
ret i32 0
}
@analias = alias void (...), bitcast (void ()* @aliasee to void (...)*)
define void @aliasee() #0 {
entry:
ret void
}