[llvm] r184590 - Revert "BlockFrequency: Saturate at 1 instead of 0 when multiplying a frequency with a branch probability."
Benjamin Kramer
benny.kra at googlemail.com
Fri Jun 21 13:20:27 PDT 2013
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.
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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