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SamplePGO - Add optimization reports.
This adds a couple of optimization remarks to the SamplePGO
transformation. When it decides to inline a hot function (to mimic the
inline stack and repeat useful inline decisions in the original build).
It will also report branch destinations. For instance, given the code
fragment:
6 if (i < 1000)
7 sum -= i;
8 else
9 sum += -i * rand();
If the 'else' branch is taken most of the time, building this code with
-Rpass=sample-profile will produce:
a.cc:9:14: remark: most popular destination for conditional branches at small.cc:6:9 [-Rpass=sample-profile]
sum += -i * rand();
^
llvm-svn: 251330
This commit is contained in:
Diego Novillo
parent
a667b6ee3c
commit
73fa815dcb
@ -387,6 +387,7 @@ SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const {
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/// \returns True if there is any inline happened.
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bool SampleProfileLoader::inlineHotFunctions(Function &F) {
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bool Changed = false;
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LLVMContext &Ctx = F.getContext();
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while (true) {
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bool LocalChanged = false;
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SmallVector<CallInst *, 10> CIS;
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@ -403,8 +404,17 @@ bool SampleProfileLoader::inlineHotFunctions(Function &F) {
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}
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for (auto CI : CIS) {
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InlineFunctionInfo IFI;
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if (InlineFunction(CI, IFI))
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Function *CalledFunction = CI->getCalledFunction();
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DebugLoc DLoc = CI->getDebugLoc();
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uint64_t NumSamples = findCalleeFunctionSamples(*CI)->getTotalSamples();
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if (InlineFunction(CI, IFI)) {
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LocalChanged = true;
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emitOptimizationRemark(Ctx, DEBUG_TYPE, F, DLoc,
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Twine("inlined hot callee '") +
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CalledFunction->getName() + "' with " +
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Twine(NumSamples) + " samples into '" +
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F.getName() + "'");
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}
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}
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if (LocalChanged) {
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Changed = true;
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@ -724,7 +734,8 @@ void SampleProfileLoader::propagateWeights(Function &F) {
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// Generate MD_prof metadata for every branch instruction using the
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// edge weights computed during propagation.
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DEBUG(dbgs() << "\nPropagation complete. Setting branch weights\n");
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MDBuilder MDB(F.getContext());
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LLVMContext &Ctx = F.getContext();
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MDBuilder MDB(Ctx);
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for (auto &BI : F) {
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BasicBlock *BB = &BI;
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TerminatorInst *TI = BB->getTerminator();
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@ -736,7 +747,9 @@ void SampleProfileLoader::propagateWeights(Function &F) {
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DEBUG(dbgs() << "\nGetting weights for branch at line "
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<< TI->getDebugLoc().getLine() << ".\n");
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SmallVector<uint32_t, 4> Weights;
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bool AllWeightsZero = true;
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uint32_t MaxWeight = 0;
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BasicBlock *MaxDestBB = nullptr;
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DebugLoc MaxDestLoc;
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for (unsigned I = 0; I < TI->getNumSuccessors(); ++I) {
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BasicBlock *Succ = TI->getSuccessor(I);
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Edge E = std::make_pair(BB, Succ);
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@ -750,16 +763,27 @@ void SampleProfileLoader::propagateWeights(Function &F) {
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Weight = std::numeric_limits<uint32_t>::max();
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}
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Weights.push_back(static_cast<uint32_t>(Weight));
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if (Weight != 0)
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AllWeightsZero = false;
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if (Weight != 0) {
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if (Weight > MaxWeight) {
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MaxWeight = Weight;
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MaxDestBB = Succ;
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MaxDestLoc = Succ->getFirstNonPHIOrDbgOrLifetime()->getDebugLoc();
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}
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}
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}
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// Only set weights if there is at least one non-zero weight.
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// In any other case, let the analyzer set weights.
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if (!AllWeightsZero) {
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if (MaxWeight > 0) {
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DEBUG(dbgs() << "SUCCESS. Found non-zero weights.\n");
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TI->setMetadata(llvm::LLVMContext::MD_prof,
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MDB.createBranchWeights(Weights));
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DebugLoc BranchLoc = TI->getDebugLoc();
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emitOptimizationRemark(
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Ctx, DEBUG_TYPE, F, MaxDestLoc,
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Twine("most popular destination for conditional branches at ") +
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BranchLoc->getFilename() + ":" + Twine(BranchLoc.getLine()) +
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":" + Twine(BranchLoc.getCol()));
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} else {
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DEBUG(dbgs() << "SKIPPED. All branch weights are zero.\n");
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}
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7
test/Transforms/SampleProfile/Inputs/remarks.prof
Normal file
7
test/Transforms/SampleProfile/Inputs/remarks.prof
Normal file
@ -0,0 +1,7 @@
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main:623868:0
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0: 0
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0: _Z3foov:623868
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3: 18346
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4: 0
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6: 19475
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2: 18305
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185
test/Transforms/SampleProfile/remarks.ll
Normal file
185
test/Transforms/SampleProfile/remarks.ll
Normal file
@ -0,0 +1,185 @@
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; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/remarks.prof -S -pass-remarks=sample-profile 2>&1 | FileCheck %s
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;
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; Original test case.
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;
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; 1 #include <stdlib.h>
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; 2
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; 3 long long foo() {
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; 4 long long int sum = 0;
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; 5 for (int i = 0; i < 500000000; i++)
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; 6 if (i < 1000)
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; 7 sum -= i;
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; 8 else
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; 9 sum += -i * rand();
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; 10 return sum;
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; 11 }
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; 12
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; 13 int main() { return foo() > 0; }
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; We are expecting foo() to be inlined in main() (almost all the cycles are
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; spent inside foo).
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; CHECK: remark: remarks.cc:13:21: inlined hot callee '_Z3foov' with 623868 samples into 'main'
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; The back edge for the loop is the hottest edge in the loop subgraph.
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; CHECK: remark: remarks.cc:6:9: most popular destination for conditional branches at remarks.cc:5:3
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; The predicate almost always chooses the 'else' branch.
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; CHECK: remark: remarks.cc:9:15: most popular destination for conditional branches at remarks.cc:6:9
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; Function Attrs: nounwind uwtable
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define i64 @_Z3foov() #0 {
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entry:
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%sum = alloca i64, align 8
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%i = alloca i32, align 4
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%0 = bitcast i64* %sum to i8*, !dbg !19
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call void @llvm.lifetime.start(i64 8, i8* %0) #4, !dbg !19
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call void @llvm.dbg.declare(metadata i64* %sum, metadata !9, metadata !20), !dbg !21
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store i64 0, i64* %sum, align 8, !dbg !21, !tbaa !22
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%1 = bitcast i32* %i to i8*, !dbg !26
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call void @llvm.lifetime.start(i64 4, i8* %1) #4, !dbg !26
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call void @llvm.dbg.declare(metadata i32* %i, metadata !10, metadata !20), !dbg !27
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store i32 0, i32* %i, align 4, !dbg !27, !tbaa !28
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br label %for.cond, !dbg !26
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for.cond: ; preds = %for.inc, %entry
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%2 = load i32, i32* %i, align 4, !dbg !30, !tbaa !28
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%cmp = icmp slt i32 %2, 500000000, !dbg !34
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br i1 %cmp, label %for.body, label %for.cond.cleanup, !dbg !35
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for.cond.cleanup: ; preds = %for.cond
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%3 = bitcast i32* %i to i8*, !dbg !36
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call void @llvm.lifetime.end(i64 4, i8* %3) #4, !dbg !36
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br label %for.end
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for.body: ; preds = %for.cond
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%4 = load i32, i32* %i, align 4, !dbg !38, !tbaa !28
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%cmp1 = icmp slt i32 %4, 1000, !dbg !40
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br i1 %cmp1, label %if.then, label %if.else, !dbg !41
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if.then: ; preds = %for.body
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%5 = load i32, i32* %i, align 4, !dbg !42, !tbaa !28
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%conv = sext i32 %5 to i64, !dbg !42
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%6 = load i64, i64* %sum, align 8, !dbg !43, !tbaa !22
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%sub = sub nsw i64 %6, %conv, !dbg !43
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store i64 %sub, i64* %sum, align 8, !dbg !43, !tbaa !22
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br label %if.end, !dbg !44
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if.else: ; preds = %for.body
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%7 = load i32, i32* %i, align 4, !dbg !45, !tbaa !28
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%sub2 = sub nsw i32 0, %7, !dbg !46
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%call = call i32 @rand() #4, !dbg !47
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%mul = mul nsw i32 %sub2, %call, !dbg !48
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%conv3 = sext i32 %mul to i64, !dbg !46
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%8 = load i64, i64* %sum, align 8, !dbg !49, !tbaa !22
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%add = add nsw i64 %8, %conv3, !dbg !49
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store i64 %add, i64* %sum, align 8, !dbg !49, !tbaa !22
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br label %if.end
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if.end: ; preds = %if.else, %if.then
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br label %for.inc, !dbg !50
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for.inc: ; preds = %if.end
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%9 = load i32, i32* %i, align 4, !dbg !51, !tbaa !28
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%inc = add nsw i32 %9, 1, !dbg !51
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store i32 %inc, i32* %i, align 4, !dbg !51, !tbaa !28
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br label %for.cond, !dbg !52
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for.end: ; preds = %for.cond.cleanup
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%10 = load i64, i64* %sum, align 8, !dbg !53, !tbaa !22
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%11 = bitcast i64* %sum to i8*, !dbg !54
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call void @llvm.lifetime.end(i64 8, i8* %11) #4, !dbg !54
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ret i64 %10, !dbg !55
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}
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; Function Attrs: nounwind argmemonly
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declare void @llvm.lifetime.start(i64, i8* nocapture) #1
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; Function Attrs: nounwind readnone
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declare void @llvm.dbg.declare(metadata, metadata, metadata) #2
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; Function Attrs: nounwind
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declare i32 @rand() #3
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; Function Attrs: nounwind argmemonly
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declare void @llvm.lifetime.end(i64, i8* nocapture) #1
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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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store i32 0, i32* %retval, align 4
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%call = call i64 @_Z3foov(), !dbg !56
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%cmp = icmp sgt i64 %call, 0, !dbg !57
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%conv = zext i1 %cmp to i32, !dbg !56
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ret i32 %conv, !dbg !58
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}
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attributes #0 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
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attributes #1 = { nounwind argmemonly }
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attributes #2 = { nounwind readnone }
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attributes #3 = { nounwind "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
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attributes #4 = { nounwind }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!16, !17}
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!llvm.ident = !{!18}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 251041) (llvm/trunk 251053)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
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!1 = !DIFile(filename: "remarks.cc", directory: ".")
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!2 = !{}
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!3 = !{!4, !13}
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!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, function: i64 ()* @_Z3foov, variables: !8)
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!5 = !DISubroutineType(types: !6)
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!6 = !{!7}
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!7 = !DIBasicType(name: "long long int", size: 64, align: 64, encoding: DW_ATE_signed)
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!8 = !{!9, !10}
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!9 = !DILocalVariable(name: "sum", scope: !4, file: !1, line: 4, type: !7)
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!10 = !DILocalVariable(name: "i", scope: !11, file: !1, line: 5, type: !12)
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!11 = distinct !DILexicalBlock(scope: !4, file: !1, line: 5, column: 3)
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!12 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!13 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 13, type: !14, isLocal: false, isDefinition: true, scopeLine: 13, flags: DIFlagPrototyped, isOptimized: true, function: i32 ()* @main, variables: !2)
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!14 = !DISubroutineType(types: !15)
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!15 = !{!12}
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!16 = !{i32 2, !"Dwarf Version", i32 4}
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!17 = !{i32 2, !"Debug Info Version", i32 3}
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!18 = !{!"clang version 3.8.0 (trunk 251041) (llvm/trunk 251053)"}
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!19 = !DILocation(line: 4, column: 3, scope: !4)
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!20 = !DIExpression()
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!21 = !DILocation(line: 4, column: 17, scope: !4)
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!22 = !{!23, !23, i64 0}
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!23 = !{!"long long", !24, i64 0}
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!24 = !{!"omnipotent char", !25, i64 0}
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!25 = !{!"Simple C/C++ TBAA"}
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!26 = !DILocation(line: 5, column: 8, scope: !11)
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!27 = !DILocation(line: 5, column: 12, scope: !11)
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!28 = !{!29, !29, i64 0}
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!29 = !{!"int", !24, i64 0}
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!30 = !DILocation(line: 5, column: 19, scope: !31)
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!31 = !DILexicalBlockFile(scope: !32, file: !1, discriminator: 3)
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!32 = !DILexicalBlockFile(scope: !33, file: !1, discriminator: 1)
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!33 = distinct !DILexicalBlock(scope: !11, file: !1, line: 5, column: 3)
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!34 = !DILocation(line: 5, column: 21, scope: !33)
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!35 = !DILocation(line: 5, column: 3, scope: !11)
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!36 = !DILocation(line: 5, column: 3, scope: !37)
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!37 = !DILexicalBlockFile(scope: !33, file: !1, discriminator: 2)
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!38 = !DILocation(line: 6, column: 9, scope: !39)
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!39 = distinct !DILexicalBlock(scope: !33, file: !1, line: 6, column: 9)
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!40 = !DILocation(line: 6, column: 11, scope: !39)
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!41 = !DILocation(line: 6, column: 9, scope: !33)
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!42 = !DILocation(line: 7, column: 14, scope: !39)
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!43 = !DILocation(line: 7, column: 11, scope: !39)
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!44 = !DILocation(line: 7, column: 7, scope: !39)
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!45 = !DILocation(line: 9, column: 15, scope: !39)
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!46 = !DILocation(line: 9, column: 14, scope: !39)
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!47 = !DILocation(line: 9, column: 19, scope: !39)
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!48 = !DILocation(line: 9, column: 17, scope: !39)
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!49 = !DILocation(line: 9, column: 11, scope: !39)
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!50 = !DILocation(line: 6, column: 13, scope: !39)
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!51 = !DILocation(line: 5, column: 35, scope: !33)
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!52 = !DILocation(line: 5, column: 3, scope: !33)
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!53 = !DILocation(line: 10, column: 10, scope: !4)
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!54 = !DILocation(line: 11, column: 1, scope: !4)
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!55 = !DILocation(line: 10, column: 3, scope: !4)
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!56 = !DILocation(line: 13, column: 21, scope: !13)
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!57 = !DILocation(line: 13, column: 27, scope: !13)
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!58 = !DILocation(line: 13, column: 14, scope: !13)
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