From 302e91baf4fa041d2187e153e59bbe8c7ff5b673 Mon Sep 17 00:00:00 2001 From: Mircea Trofin Date: Thu, 23 Jul 2020 08:42:34 -0700 Subject: [PATCH] [llvm][NFC] Add comments and common-case API to MachineBlockFrequencyInfo Clarify the relation between a block's BlockFrequency and the getEntryFreq() API, and added an API for the relatively common case of finding a block's frequency relative to the entrypoint. Added / moved some comments to header. Differential Revision: https://reviews.llvm.org/D84357 --- llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h | 15 ++++++++++++++- llvm/lib/CodeGen/LiveIntervals.cpp | 4 +--- llvm/lib/CodeGen/RegAllocPBQP.cpp | 3 +-- 3 files changed, 16 insertions(+), 6 deletions(-) diff --git a/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h b/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h index 01f83a5..7ce11c7 100644 --- a/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h +++ b/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h @@ -58,9 +58,17 @@ public: /// information. Please note that initial frequency is equal to 1024. It means /// that we should not rely on the value itself, but only on the comparison to /// the other block frequencies. We do this to avoid using of floating points. - /// + /// For example, to get the frequency of a block relative to the entry block, + /// divide the integral value returned by this function (the + /// BlockFrequency::getFrequency() value) by getEntryFreq(). BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const; + /// Compute the frequency of the block, relative to the entry block. + /// This API assumes getEntryFreq() is non-zero. + float getBlockFreqRelativeToEntryBlock(const MachineBasicBlock *MBB) const { + return getBlockFreq(MBB).getFrequency() * (1.0f / getEntryFreq()); + } + Optional getBlockProfileCount(const MachineBasicBlock *MBB) const; Optional getProfileCountFromFreq(uint64_t Freq) const; @@ -70,6 +78,9 @@ public: const MachineFunction *getFunction() const; const MachineBranchProbabilityInfo *getMBPI() const; + + /// Pop up a ghostview window with the current block frequency propagation + /// rendered using dot. void view(const Twine &Name, bool isSimple = true) const; // Print the block frequency Freq to OS using the current functions entry @@ -81,6 +92,8 @@ public: raw_ostream &printBlockFreq(raw_ostream &OS, const MachineBasicBlock *MBB) const; + /// Divide a block's BlockFrequency::getFrequency() value by this value to + /// obtain the entry block - relative frequency of said block. uint64_t getEntryFreq() const; }; diff --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp index e8ee059..6539de1 100644 --- a/llvm/lib/CodeGen/LiveIntervals.cpp +++ b/llvm/lib/CodeGen/LiveIntervals.cpp @@ -868,9 +868,7 @@ float LiveIntervals::getSpillWeight(bool isDef, bool isUse, float LiveIntervals::getSpillWeight(bool isDef, bool isUse, const MachineBlockFrequencyInfo *MBFI, const MachineBasicBlock *MBB) { - BlockFrequency Freq = MBFI->getBlockFreq(MBB); - const float Scale = 1.0f / MBFI->getEntryFreq(); - return (isDef + isUse) * (Freq.getFrequency() * Scale); + return (isDef + isUse) * MBFI->getBlockFreqRelativeToEntryBlock(MBB); } LiveRange::Segment diff --git a/llvm/lib/CodeGen/RegAllocPBQP.cpp b/llvm/lib/CodeGen/RegAllocPBQP.cpp index 7590dbf..34701b7 100644 --- a/llvm/lib/CodeGen/RegAllocPBQP.cpp +++ b/llvm/lib/CodeGen/RegAllocPBQP.cpp @@ -451,8 +451,7 @@ public: unsigned DstReg = CP.getDstReg(); unsigned SrcReg = CP.getSrcReg(); - const float Scale = 1.0f / MBFI.getEntryFreq(); - PBQP::PBQPNum CBenefit = MBFI.getBlockFreq(&MBB).getFrequency() * Scale; + PBQP::PBQPNum CBenefit = MBFI.getBlockFreqRelativeToEntryBlock(&MBB); if (CP.isPhys()) { if (!MF.getRegInfo().isAllocatable(DstReg)) -- 2.7.4