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Revert "[InstrProfiling] Emit bias variable eagerly" 

This reverts commit 6660cec568 since
it was superseded by https://reviews.llvm.org/D98061.
This commit is contained in:
Petr Hosek 2021-08-10 11:23:50 -07:00
parent 97e41c004c
commit c0c1c3cf93
3 changed files with 15 additions and 36 deletions
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3
llvm/include/llvm/Transforms/Instrumentation/InstrProfiling.h
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@ -121,9 +121,6 @@ private:
/// Create a static initializer for our data, on platforms that need it,
/// and for any profile output file that was specified.
void emitInitialization();
// Emit the variable used for runtime counter relocation.
bool emitBiasVar();
};
} // end namespace llvm

42
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
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@ -551,10 +551,6 @@ bool InstrProfiling::run(
// Emit the runtime hook even if no counters are present.
bool MadeChange = emitRuntimeHook();
// Emit the bias variable in each module when counter relocation is enabled.
if (isRuntimeCounterRelocationEnabled())
MadeChange |= emitBiasVar();
// Improve compile time by avoiding linear scans when there is no work.
GlobalVariable *CoverageNamesVar =
M.getNamedGlobal(getCoverageUnusedNamesVarName());
@ -697,6 +693,21 @@ void InstrProfiling::lowerIncrement(InstrProfIncrementInst *Inc) {
if (!LI) {
IRBuilder<> Builder(&I);
GlobalVariable *Bias = M->getGlobalVariable(getInstrProfCounterBiasVarName());
if (!Bias) {
// Compiler must define this variable when runtime counter relocation
// is being used. Runtime has a weak external reference that is used
// to check whether that's the case or not.
Bias = new GlobalVariable(*M, Int64Ty, false, GlobalValue::LinkOnceODRLinkage,
Constant::getNullValue(Int64Ty),
getInstrProfCounterBiasVarName());
Bias->setVisibility(GlobalVariable::HiddenVisibility);
// A definition that's weak (linkonce_odr) without being in a COMDAT
// section wouldn't lead to link errors, but it would lead to a dead
// data word from every TU but one. Putting it in COMDAT ensures there
// will be exactly one data slot in the link.
if (TT.supportsCOMDAT())
Bias->setComdat(M->getOrInsertComdat(Bias->getName()));
}
LI = Builder.CreateLoad(Int64Ty, Bias);
}
auto *Add = Builder.CreateAdd(Builder.CreatePtrToInt(Addr, Int64Ty), LI);
@ -1183,26 +1194,3 @@ void InstrProfiling::emitInitialization() {
appendToGlobalCtors(*M, F, 0);
}
bool InstrProfiling::emitBiasVar() {
// Module already provided its own variable, nothin to do.
if (M->getGlobalVariable(getInstrProfCounterBiasVarName()))
return false;
// Compiler must define this variable when runtime counter relocation
// is being used. Runtime has a weak external reference that is used
// to check whether that's the case or not.
Type *Int64Ty = Type::getInt64Ty(M->getContext());
auto *Bias = new GlobalVariable(*M, Int64Ty, false, GlobalValue::LinkOnceODRLinkage,
Constant::getNullValue(Int64Ty),
getInstrProfCounterBiasVarName());
Bias->setVisibility(GlobalVariable::HiddenVisibility);
// A definition that's weak (linkonce_odr) without being in a COMDAT
// section wouldn't lead to link errors, but it would lead to a dead
// data word from every TU but one. Putting it in COMDAT ensures there
// will be exactly one data slot in the link.
if (TT.supportsCOMDAT())
Bias->setComdat(M->getOrInsertComdat(Bias->getName()));
return true;
}

6
llvm/test/Instrumentation/InstrProfiling/bias-var.ll
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@ -1,6 +0,0 @@
; RUN: opt < %s -S -instrprof -runtime-counter-relocation | FileCheck -check-prefixes=RELOC %s
target triple = "x86_64-unknown-linux-gnu"
; RELOC: $__llvm_profile_counter_bias = comdat any
; RELOC: @__llvm_profile_counter_bias = linkonce_odr hidden global i64 0, comdat