[llvm] r184590 - Revert "BlockFrequency: Saturate at 1 instead of 0 when multiplying a frequency with a branch probability."
Hal Finkel
hfinkel at anl.gov
Sat Jun 22 21:51:16 PDT 2013
----- Original Message -----
> Author: d0k
> Date: Fri Jun 21 15:20:27 2013
> New Revision: 184590
>
> URL: http://llvm.org/viewvc/llvm-project?rev=184590&view=rev
> Log:
> Revert "BlockFrequency: Saturate at 1 instead of 0 when multiplying a
> frequency with a branch probability."
>
> This reverts commit r184584. Breaks PPC selfhost.
That seems odd. Which build was this? Do you have any additional details?
Thanks again,
Hal
>
> Removed:
> llvm/trunk/test/Analysis/BlockFrequencyInfo/singularity.ll
> Modified:
> llvm/trunk/include/llvm/Support/BlockFrequency.h
> llvm/trunk/lib/Support/BlockFrequency.cpp
> llvm/trunk/unittests/Support/BlockFrequencyTest.cpp
>
> Modified: llvm/trunk/include/llvm/Support/BlockFrequency.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/BlockFrequency.h?rev=184590&r1=184589&r2=184590&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/BlockFrequency.h (original)
> +++ llvm/trunk/include/llvm/Support/BlockFrequency.h Fri Jun 21
> 15:20:27 2013
> @@ -30,20 +30,12 @@ class BlockFrequency {
> public:
> BlockFrequency(uint64_t Freq = 0) : Frequency(Freq) { }
>
> - /// \brief Returns the frequency of the entry block of the
> function.
> static uint64_t getEntryFrequency() { return ENTRY_FREQ; }
> -
> - /// \brief Returns the frequency as a fixpoint number scaled by
> the entry
> - /// frequency.
> uint64_t getFrequency() const { return Frequency; }
>
> - /// \brief Multiplies with a branch probability. The computation
> will never
> - /// overflow. If the result is equal to zero but the input wasn't
> this method
> - /// will return a frequency of one.
> BlockFrequency &operator*=(const BranchProbability &Prob);
> const BlockFrequency operator*(const BranchProbability &Prob)
> const;
>
> - /// \brief Adds another block frequency using saturating
> arithmetic.
> BlockFrequency &operator+=(const BlockFrequency &Freq);
> const BlockFrequency operator+(const BlockFrequency &Freq) const;
>
>
> Modified: llvm/trunk/lib/Support/BlockFrequency.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/BlockFrequency.cpp?rev=184590&r1=184589&r2=184590&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Support/BlockFrequency.cpp (original)
> +++ llvm/trunk/lib/Support/BlockFrequency.cpp Fri Jun 21 15:20:27
> 2013
> @@ -65,9 +65,6 @@ uint64_t div96bit(uint64_t W[2], uint32_
>
>
> BlockFrequency &BlockFrequency::operator*=(const BranchProbability
> &Prob) {
> - if (Frequency == 0)
> - return *this;
> -
> uint32_t n = Prob.getNumerator();
> uint32_t d = Prob.getDenominator();
>
> @@ -87,15 +84,10 @@ BlockFrequency &BlockFrequency::operator
> // 64-bit.
> mult96bit(Frequency, n, W);
> Frequency = div96bit(W, d);
> - } else {
> - // Fast case.
> - Frequency = mulRes / d;
> + return *this;
> }
>
> - // Limit the result to 1; 0 is a sentinel value. This keeps
> BlockFrequencyInfo
> - // from getting stuck at zero frequencies just because a value
> became too
> - // small to be represented as a BlockFrequency.
> - Frequency = (n == 0 || Frequency != 0) ? Frequency : 1;
> + Frequency = mulRes / d;
> return *this;
> }
>
>
> Removed: llvm/trunk/test/Analysis/BlockFrequencyInfo/singularity.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BlockFrequencyInfo/singularity.ll?rev=184589&view=auto
> ==============================================================================
> --- llvm/trunk/test/Analysis/BlockFrequencyInfo/singularity.ll
> (original)
> +++ llvm/trunk/test/Analysis/BlockFrequencyInfo/singularity.ll
> (removed)
> @@ -1,65 +0,0 @@
> -; RUN: opt < %s -analyze -block-freq | FileCheck %s
> -; PR16402
> -
> -define void @test1(i32 %n) nounwind {
> -entry:
> - %call = tail call i32* @cond() nounwind
> - %tobool = icmp eq i32* %call, null
> - br i1 %tobool, label %land.lhs.true, label %if.end
> -
> -land.lhs.true: ; preds = %entry
> - %call1 = tail call i32* @cond() nounwind
> - %tobool2 = icmp eq i32* %call1, null
> - br i1 %tobool2, label %land.lhs.true3, label %if.end
> -
> -land.lhs.true3: ; preds =
> %land.lhs.true
> - %call4 = tail call i32* @cond() nounwind
> - %tobool5 = icmp eq i32* %call4, null
> - br i1 %tobool5, label %land.lhs.true6, label %if.end
> -
> -land.lhs.true6: ; preds =
> %land.lhs.true3
> - %call7 = tail call i32* @cond() nounwind
> - %tobool8 = icmp eq i32* %call7, null
> - br i1 %tobool8, label %land.lhs.true9, label %if.end
> -
> -land.lhs.true9: ; preds =
> %land.lhs.true6
> - %call10 = tail call i32* @cond() nounwind
> - %tobool11 = icmp eq i32* %call10, null
> - br i1 %tobool11, label %land.lhs.true12, label %if.end
> -
> -land.lhs.true12: ; preds =
> %land.lhs.true9
> - %call13 = tail call i32* @cond() nounwind
> - %tobool14 = icmp eq i32* %call13, null
> - br i1 %tobool14, label %land.lhs.true15, label %if.end
> -
> -land.lhs.true15: ; preds =
> %land.lhs.true12
> - %call16 = tail call i32* @cond() nounwind
> - %tobool17 = icmp eq i32* %call16, null
> - br i1 %tobool17, label %for.cond.preheader, label %if.end
> -
> -for.cond.preheader: ; preds =
> %land.lhs.true15
> - %cmp21 = icmp eq i32 %n, 0
> - br i1 %cmp21, label %for.end, label %for.body
> -
> -for.body: ; preds =
> %for.cond.preheader, %for.body
> - %i.022 = phi i32 [ %inc, %for.body ], [ 0, %for.cond.preheader ]
> - %call18 = tail call i32 @call() nounwind
> - %inc = add nsw i32 %i.022, 1
> - %cmp = icmp eq i32 %inc, %n
> - br i1 %cmp, label %for.end, label %for.body
> -
> -for.end: ; preds =
> %for.body, %for.cond.preheader
> - %call19 = tail call i32* @cond() nounwind
> - br label %if.end
> -
> -if.end: ; preds =
> %land.lhs.true15, %land.lhs.true12, %land.lhs.true9,
> %land.lhs.true6, %land.lhs.true3, %land.lhs.true, %entry, %for.end
> - ret void
> -
> -; CHECK: entry = 1024
> -; CHECK-NOT: for.body = 0
> -; CHECK-NOT: for.end = 0
> -}
> -
> -declare i32* @cond() nounwind
> -
> -declare i32 @call() nounwind
>
> Modified: llvm/trunk/unittests/Support/BlockFrequencyTest.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/BlockFrequencyTest.cpp?rev=184590&r1=184589&r2=184590&view=diff
> ==============================================================================
> --- llvm/trunk/unittests/Support/BlockFrequencyTest.cpp (original)
> +++ llvm/trunk/unittests/Support/BlockFrequencyTest.cpp Fri Jun 21
> 15:20:27 2013
> @@ -8,22 +8,11 @@ using namespace llvm;
>
> namespace {
>
> -TEST(BlockFrequencyTest, ZeroToZero) {
> - BlockFrequency Freq(0);
> - BranchProbability Prob(UINT32_MAX - 1, UINT32_MAX);
> - Freq *= Prob;
> - EXPECT_EQ(Freq.getFrequency(), 0u);
> -
> - Freq = 1;
> - Freq *= BranchProbability::getZero();
> - EXPECT_EQ(Freq.getFrequency(), 0u);
> -}
> -
> TEST(BlockFrequencyTest, OneToZero) {
> BlockFrequency Freq(1);
> BranchProbability Prob(UINT32_MAX - 1, UINT32_MAX);
> Freq *= Prob;
> - EXPECT_EQ(Freq.getFrequency(), 1u);
> + EXPECT_EQ(Freq.getFrequency(), 0u);
> }
>
> TEST(BlockFrequencyTest, OneToOne) {
>
>
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>
--
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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