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[LoopUnswitch] Remove BFI usage (dead code)
Chandler mentioned at the last social that the need for BFI in the new pass manager was causing a slight hiccup for this pass. Given this code has been checked in, but off for over a year, it makes sense to just remove it for now. Note that there's nothing wrong with the general idea - it's actually a quite good one - and once we have the infrastructure in place to implement this without the full recompuation on every loop, we absolutely should. llvm-svn: 294715
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@ -77,19 +77,6 @@ static cl::opt<unsigned>
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Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"),
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cl::init(100), cl::Hidden);
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static cl::opt<bool>
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LoopUnswitchWithBlockFrequency("loop-unswitch-with-block-frequency",
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cl::init(false), cl::Hidden,
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cl::desc("Enable the use of the block frequency analysis to access PGO "
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"heuristics to minimize code growth in cold regions."));
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static cl::opt<unsigned>
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ColdnessThreshold("loop-unswitch-coldness-threshold", cl::init(1), cl::Hidden,
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cl::desc("Coldness threshold in percentage. The loop header frequency "
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"(relative to the entry frequency) is compared with this "
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"threshold to determine if non-trivial unswitching should be "
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"enabled."));
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namespace {
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class LUAnalysisCache {
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@ -174,13 +161,6 @@ namespace {
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LUAnalysisCache BranchesInfo;
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bool EnabledPGO;
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// BFI and ColdEntryFreq are only used when PGO and
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// LoopUnswitchWithBlockFrequency are enabled.
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BlockFrequencyInfo BFI;
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BlockFrequency ColdEntryFreq;
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bool OptimizeForSize;
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bool redoLoop;
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@ -457,19 +437,6 @@ bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
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if (SanitizeMemory)
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computeLoopSafetyInfo(&SafetyInfo, L);
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EnabledPGO = F->getEntryCount().hasValue();
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if (LoopUnswitchWithBlockFrequency && EnabledPGO) {
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BranchProbabilityInfo BPI(*F, *LI);
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BFI.calculate(*L->getHeader()->getParent(), BPI, *LI);
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// Use BranchProbability to compute a minimum frequency based on
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// function entry baseline frequency. Loops with headers below this
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// frequency are considered as cold.
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const BranchProbability ColdProb(ColdnessThreshold, 100);
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ColdEntryFreq = BlockFrequency(BFI.getEntryFreq()) * ColdProb;
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}
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bool Changed = false;
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do {
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assert(currentLoop->isLCSSAForm(*DT));
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@ -581,16 +548,6 @@ bool LoopUnswitch::processCurrentLoop() {
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loopHeader->getParent()->hasFnAttribute(Attribute::OptimizeForSize))
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return false;
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if (LoopUnswitchWithBlockFrequency && EnabledPGO) {
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// Compute the weighted frequency of the hottest block in the
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// loop (loopHeader in this case since inner loops should be
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// processed before outer loop). If it is less than ColdFrequency,
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// we should not unswitch.
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BlockFrequency LoopEntryFreq = BFI.getBlockFreq(loopHeader);
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if (LoopEntryFreq < ColdEntryFreq)
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return false;
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}
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for (IntrinsicInst *Guard : Guards) {
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Value *LoopCond =
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FindLIVLoopCondition(Guard->getOperand(0), currentLoop, Changed);
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@ -1,52 +0,0 @@
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; RUN: opt < %s -loop-unswitch -loop-unswitch-with-block-frequency -S 2>&1 | FileCheck %s
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;; trivial condition should be unswithed regardless of coldness.
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define i32 @test1(i1 %cond1, i1 %cond2) !prof !1 {
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br i1 %cond1, label %loop_begin, label %loop_exit, !prof !0
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loop_begin:
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; CHECK: br i1 true, label %continue, label %loop_exit.loopexit
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br i1 %cond2, label %continue, label %loop_exit ; trivial condition
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continue:
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call void @some_func1() noreturn nounwind
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br label %loop_begin
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loop_exit:
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ret i32 0
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}
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;; cold non-trivial condition should not be unswitched.
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define i32 @test2(i32* %var, i1 %cond1, i1 %cond2) !prof !1 {
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br i1 %cond1, label %loop_begin, label %loop_exit, !prof !0
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loop_begin:
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store i32 1, i32* %var
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; CHECK: br i1 %cond2, label %continue1, label %continue2
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br i1 %cond2, label %continue1, label %continue2 ; non-trivial condition
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continue1:
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call void @some_func1() noreturn nounwind
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br label %joint
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continue2:
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call void @some_func2() noreturn nounwind
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br label %joint
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joint:
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;; unswitching will duplicate these calls.
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call void @some_func3() noreturn nounwind
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call void @some_func4() noreturn nounwind
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br label %loop_begin
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loop_exit:
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ret i32 0
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}
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declare void @some_func1() noreturn
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declare void @some_func2() noreturn
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declare void @some_func3() noreturn
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declare void @some_func4() noreturn
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!0 = !{!"branch_weights", i32 1, i32 100000000}
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!1 = !{!"function_entry_count", i64 100}
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