Revert "BlockFrequency: Saturate at 1 instead of 0 when multiplying a frequency with a branch probability."
This reverts commit r184584. Breaks PPC selfhost. llvm-svn: 184590
This commit is contained in:
Benjamin Kramer
parent
7b7b0b9f7d
commit
bfb84d0bd6
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@ -30,20 +30,12 @@ class BlockFrequency {
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public:
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BlockFrequency(uint64_t Freq = 0) : Frequency(Freq) { }
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/// \brief Returns the frequency of the entry block of the function.
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static uint64_t getEntryFrequency() { return ENTRY_FREQ; }
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/// \brief Returns the frequency as a fixpoint number scaled by the entry
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/// frequency.
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uint64_t getFrequency() const { return Frequency; }
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/// \brief Multiplies with a branch probability. The computation will never
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/// overflow. If the result is equal to zero but the input wasn't this method
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/// will return a frequency of one.
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BlockFrequency &operator*=(const BranchProbability &Prob);
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const BlockFrequency operator*(const BranchProbability &Prob) const;
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/// \brief Adds another block frequency using saturating arithmetic.
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BlockFrequency &operator+=(const BlockFrequency &Freq);
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const BlockFrequency operator+(const BlockFrequency &Freq) const;
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@ -65,9 +65,6 @@ uint64_t div96bit(uint64_t W[2], uint32_t D) {
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BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
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if (Frequency == 0)
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return *this;
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uint32_t n = Prob.getNumerator();
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uint32_t d = Prob.getDenominator();
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@ -87,15 +84,10 @@ BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
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// 64-bit.
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mult96bit(Frequency, n, W);
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Frequency = div96bit(W, d);
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} else {
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// Fast case.
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Frequency = mulRes / d;
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return *this;
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}
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// Limit the result to 1; 0 is a sentinel value. This keeps BlockFrequencyInfo
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// from getting stuck at zero frequencies just because a value became too
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// small to be represented as a BlockFrequency.
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Frequency = (n == 0 || Frequency != 0) ? Frequency : 1;
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Frequency = mulRes / d;
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return *this;
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}
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@ -1,65 +0,0 @@
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; RUN: opt < %s -analyze -block-freq | FileCheck %s
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; PR16402
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define void @test1(i32 %n) nounwind {
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entry:
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%call = tail call i32* @cond() nounwind
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%tobool = icmp eq i32* %call, null
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br i1 %tobool, label %land.lhs.true, label %if.end
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land.lhs.true: ; preds = %entry
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%call1 = tail call i32* @cond() nounwind
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%tobool2 = icmp eq i32* %call1, null
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br i1 %tobool2, label %land.lhs.true3, label %if.end
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land.lhs.true3: ; preds = %land.lhs.true
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%call4 = tail call i32* @cond() nounwind
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%tobool5 = icmp eq i32* %call4, null
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br i1 %tobool5, label %land.lhs.true6, label %if.end
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land.lhs.true6: ; preds = %land.lhs.true3
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%call7 = tail call i32* @cond() nounwind
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%tobool8 = icmp eq i32* %call7, null
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br i1 %tobool8, label %land.lhs.true9, label %if.end
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land.lhs.true9: ; preds = %land.lhs.true6
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%call10 = tail call i32* @cond() nounwind
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%tobool11 = icmp eq i32* %call10, null
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br i1 %tobool11, label %land.lhs.true12, label %if.end
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land.lhs.true12: ; preds = %land.lhs.true9
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%call13 = tail call i32* @cond() nounwind
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%tobool14 = icmp eq i32* %call13, null
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br i1 %tobool14, label %land.lhs.true15, label %if.end
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land.lhs.true15: ; preds = %land.lhs.true12
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%call16 = tail call i32* @cond() nounwind
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%tobool17 = icmp eq i32* %call16, null
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br i1 %tobool17, label %for.cond.preheader, label %if.end
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for.cond.preheader: ; preds = %land.lhs.true15
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%cmp21 = icmp eq i32 %n, 0
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br i1 %cmp21, label %for.end, label %for.body
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for.body: ; preds = %for.cond.preheader, %for.body
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%i.022 = phi i32 [ %inc, %for.body ], [ 0, %for.cond.preheader ]
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%call18 = tail call i32 @call() nounwind
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%inc = add nsw i32 %i.022, 1
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%cmp = icmp eq i32 %inc, %n
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br i1 %cmp, label %for.end, label %for.body
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for.end: ; preds = %for.body, %for.cond.preheader
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%call19 = tail call i32* @cond() nounwind
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br label %if.end
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if.end: ; preds = %land.lhs.true15, %land.lhs.true12, %land.lhs.true9, %land.lhs.true6, %land.lhs.true3, %land.lhs.true, %entry, %for.end
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ret void
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; CHECK: entry = 1024
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; CHECK-NOT: for.body = 0
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; CHECK-NOT: for.end = 0
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}
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declare i32* @cond() nounwind
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declare i32 @call() nounwind
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@ -8,22 +8,11 @@ using namespace llvm;
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namespace {
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TEST(BlockFrequencyTest, ZeroToZero) {
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BlockFrequency Freq(0);
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BranchProbability Prob(UINT32_MAX - 1, UINT32_MAX);
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Freq *= Prob;
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EXPECT_EQ(Freq.getFrequency(), 0u);
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Freq = 1;
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Freq *= BranchProbability::getZero();
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EXPECT_EQ(Freq.getFrequency(), 0u);
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}
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TEST(BlockFrequencyTest, OneToZero) {
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BlockFrequency Freq(1);
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BranchProbability Prob(UINT32_MAX - 1, UINT32_MAX);
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Freq *= Prob;
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EXPECT_EQ(Freq.getFrequency(), 1u);
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EXPECT_EQ(Freq.getFrequency(), 0u);
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}
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TEST(BlockFrequencyTest, OneToOne) {
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