[llvm] r311647 - Model cache size and associativity in TargetTransformInfo
Tobias Grosser via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 25 10:29:40 PDT 2017
On Fri, Aug 25, 2017, at 19:20, Craig Topper via llvm-commits wrote:
> clang doesn't support -mtune. But we do have -march. llc calls it -mcpu.
> "skylake" refers to the mobile and desktop version with 4-way
> associativity. "skylake-avx512" refers to the Xeon server version.
The X86TargetTransformInfo seems to only refer to instruction set
properties. I can check for AVX512 && !Atom. Maybe this will give me the
skylake-avx512. However, this seems rather encrypted. I should probably
look for some better alternative. Any idea?
// Attempt to lookup cost.
if (ST->hasCDI())
if (const auto *Entry = CostTableLookup(AVX512CDCostTbl, ISD, MTy))
return LT.first * Entry->Cost;
if (ST->hasBWI())
if (const auto *Entry = CostTableLookup(AVX512BWCostTbl, ISD, MTy))
return LT.first * Entry->Cost;
if (ST->hasAVX512())
Best,
Tobias
>
> ~Craig
>
> On Fri, Aug 25, 2017 at 10:11 AM, Tobias Grosser <tobias at grosser.es>
> wrote:
>
> > On Thu, Aug 24, 2017, at 23:39, Craig Topper via llvm-commits wrote:
> > > I believe Skylake client's L2 associativity is only 4 way. While Skylake
> > > server has a much larger L2 with more associativity.
> > >
> > > Is this something we should get from CPUID if the user does -mcpu=native?
> >
> > I was so glad that -- according to 7-cpu -- all have the same
> > characteristics. But it seems I indeed overlooked the 4way associativity
> > of skylake.
> >
> > I wonder what would be the best way to model this. Are there different
> > mtune flags for Skylake server and client? Gcc distinguishes betweek
> > skylake and ‘skylake-avx512’? Are these the two variants you talk about?
> >
> > Best,
> > Tobias
> >
> > > ~Craig
> > >
> > > On Thu, Aug 24, 2017 at 2:46 AM, Tobias Grosser via llvm-commits <
> > > llvm-commits at lists.llvm.org> wrote:
> > >
> > > > Author: grosser
> > > > Date: Thu Aug 24 02:46:25 2017
> > > > New Revision: 311647
> > > >
> > > > URL: http://llvm.org/viewvc/llvm-project?rev=311647&view=rev
> > > > Log:
> > > > Model cache size and associativity in TargetTransformInfo
> > > >
> > > > Summary:
> > > > We add the precise cache sizes and associativity for the following
> > Intel
> > > > architectures:
> > > >
> > > > - Penry
> > > > - Nehalem
> > > > - Westmere
> > > > - Sandy Bridge
> > > > - Ivy Bridge
> > > > - Haswell
> > > > - Broadwell
> > > > - Skylake
> > > > - Kabylake
> > > >
> > > > Polly uses since several months a performance model for BLAS
> > computations
> > > > that
> > > > derives optimal cache and register tile sizes from cache and latency
> > > > information (based on ideas from "Analytical Modeling Is Enough for
> > > > High-Performance BLIS", by Tze Meng Low published at TOMS 2016).
> > > > While bootstrapping this model, these target values have been kept in
> > > > Polly.
> > > > However, as our implementation is now rather mature, it seems time to
> > teach
> > > > LLVM itself about cache sizes.
> > > >
> > > > Interestingly, L1 and L2 cache sizes are pretty constant across
> > > > micro-architectures, hence a set of architecture specific default
> > values
> > > > seems like a good start. They can be expanded to more target specific
> > > > values,
> > > > in case certain newer architectures require different values. For now
> > a set
> > > > of Intel architectures are provided.
> > > >
> > > > Just as a little teaser, for a simple gemm kernel this model allows us
> > to
> > > > improve performance from 1.2s to 0.27s. For gemm kernels with less
> > optimal
> > > > memory layouts even larger speedups can be reported.
> > > >
> > > > Reviewers: Meinersbur, bollu, singam-sanjay, hfinkel, gareevroman,
> > fhahn,
> > > > sebpop, efriedma, asb
> > > >
> > > > Reviewed By: fhahn, asb
> > > >
> > > > Subscribers: lsaba, asb, pollydev, llvm-commits
> > > >
> > > > Differential Revision: https://reviews.llvm.org/D37051
> > > >
> > > > Modified:
> > > > llvm/trunk/include/llvm/Analysis/TargetTransformInfo.h
> > > > llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
> > > > llvm/trunk/lib/Analysis/TargetTransformInfo.cpp
> > > > llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp
> > > > llvm/trunk/lib/Target/X86/X86TargetTransformInfo.h
> > > >
> > > > Modified: llvm/trunk/include/llvm/Analysis/TargetTransformInfo.h
> > > > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/
> > llvm/Analysis/
> > > > TargetTransformInfo.h?rev=311647&r1=311646&r2=311647&view=diff
> > > > ============================================================
> > > > ==================
> > > > --- llvm/trunk/include/llvm/Analysis/TargetTransformInfo.h (original)
> > > > +++ llvm/trunk/include/llvm/Analysis/TargetTransformInfo.h Thu Aug 24
> > > > 02:46:25 2017
> > > > @@ -603,6 +603,22 @@ public:
> > > > /// \return The size of a cache line in bytes.
> > > > unsigned getCacheLineSize() const;
> > > >
> > > > + /// The possible cache levels
> > > > + enum class CacheLevel {
> > > > + L1D, // The L1 data cache
> > > > + L2D, // The L2 data cache
> > > > +
> > > > + // We currently do not model L3 caches, as their sizes differ
> > widely
> > > > between
> > > > + // microarchitectures. Also, we currently do not have a use for L3
> > > > cache
> > > > + // size modeling yet.
> > > > + };
> > > > +
> > > > + /// \return The size of the cache level in bytes, if available.
> > > > + llvm::Optional<unsigned> getCacheSize(CacheLevel Level) const;
> > > > +
> > > > + /// \return The associativity of the cache level, if available.
> > > > + llvm::Optional<unsigned> getCacheAssociativity(CacheLevel Level)
> > const;
> > > > +
> > > > /// \return How much before a load we should place the prefetch
> > > > instruction.
> > > > /// This is currently measured in number of instructions.
> > > > unsigned getPrefetchDistance() const;
> > > > @@ -937,6 +953,8 @@ public:
> > > > virtual bool shouldConsiderAddressTypePromotion(
> > > > const Instruction &I, bool &AllowPromotionWithoutCommonHeader)
> > = 0;
> > > > virtual unsigned getCacheLineSize() = 0;
> > > > + virtual llvm::Optional<unsigned> getCacheSize(CacheLevel Level) = 0;
> > > > + virtual llvm::Optional<unsigned> getCacheAssociativity(CacheLevel
> > > > Level) = 0;
> > > > virtual unsigned getPrefetchDistance() = 0;
> > > > virtual unsigned getMinPrefetchStride() = 0;
> > > > virtual unsigned getMaxPrefetchIterationsAhead() = 0;
> > > > @@ -1209,6 +1227,12 @@ public:
> > > > unsigned getCacheLineSize() override {
> > > > return Impl.getCacheLineSize();
> > > > }
> > > > + llvm::Optional<unsigned> getCacheSize(CacheLevel Level) override {
> > > > + return Impl.getCacheSize(Level);
> > > > + }
> > > > + llvm::Optional<unsigned> getCacheAssociativity(CacheLevel Level)
> > > > override {
> > > > + return Impl.getCacheAssociativity(Level);
> > > > + }
> > > > unsigned getPrefetchDistance() override { return
> > > > Impl.getPrefetchDistance(); }
> > > > unsigned getMinPrefetchStride() override {
> > > > return Impl.getMinPrefetchStride();
> > > >
> > > > Modified: llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
> > > > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/
> > llvm/Analysis/
> > > > TargetTransformInfoImpl.h?rev=311647&r1=311646&r2=311647&view=diff
> > > > ============================================================
> > > > ==================
> > > > --- llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
> > (original)
> > > > +++ llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h Thu
> > Aug 24
> > > > 02:46:25 2017
> > > > @@ -340,6 +340,29 @@ public:
> > > >
> > > > unsigned getCacheLineSize() { return 0; }
> > > >
> > > > + llvm::Optional<unsigned> getCacheSize(TargetTransformInfo::
> > CacheLevel
> > > > Level) {
> > > > + switch (Level) {
> > > > + case TargetTransformInfo::CacheLevel::L1D:
> > > > + LLVM_FALLTHROUGH;
> > > > + case TargetTransformInfo::CacheLevel::L2D:
> > > > + return llvm::Optional<unsigned>();
> > > > + }
> > > > +
> > > > + llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
> > > > + }
> > > > +
> > > > + llvm::Optional<unsigned> getCacheAssociativity(
> > > > + TargetTransformInfo::CacheLevel Level) {
> > > > + switch (Level) {
> > > > + case TargetTransformInfo::CacheLevel::L1D:
> > > > + LLVM_FALLTHROUGH;
> > > > + case TargetTransformInfo::CacheLevel::L2D:
> > > > + return llvm::Optional<unsigned>();
> > > > + }
> > > > +
> > > > + llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
> > > > + }
> > > > +
> > > > unsigned getPrefetchDistance() { return 0; }
> > > >
> > > > unsigned getMinPrefetchStride() { return 1; }
> > > >
> > > > Modified: llvm/trunk/lib/Analysis/TargetTransformInfo.cpp
> > > > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> > > > Analysis/TargetTransformInfo.cpp?rev=311647&r1=311646&r2=
> > 311647&view=diff
> > > > ============================================================
> > > > ==================
> > > > --- llvm/trunk/lib/Analysis/TargetTransformInfo.cpp (original)
> > > > +++ llvm/trunk/lib/Analysis/TargetTransformInfo.cpp Thu Aug 24
> > 02:46:25
> > > > 2017
> > > > @@ -321,6 +321,16 @@ unsigned TargetTransformInfo::getCacheLi
> > > > return TTIImpl->getCacheLineSize();
> > > > }
> > > >
> > > > +llvm::Optional<unsigned> TargetTransformInfo::getCacheSize(CacheLevel
> > > > Level)
> > > > + const {
> > > > + return TTIImpl->getCacheSize(Level);
> > > > +}
> > > > +
> > > > +llvm::Optional<unsigned> TargetTransformInfo::getCacheAssociativity(
> > > > + CacheLevel Level) const {
> > > > + return TTIImpl->getCacheAssociativity(Level);
> > > > +}
> > > > +
> > > > unsigned TargetTransformInfo::getPrefetchDistance() const {
> > > > return TTIImpl->getPrefetchDistance();
> > > > }
> > > >
> > > > Modified: llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp
> > > > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/
> > > > X86/X86TargetTransformInfo.cpp?rev=311647&r1=311646&r2=
> > 311647&view=diff
> > > > ============================================================
> > > > ==================
> > > > --- llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp (original)
> > > > +++ llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp Thu Aug 24
> > > > 02:46:25 2017
> > > > @@ -66,6 +66,57 @@ X86TTIImpl::getPopcntSupport(unsigned Ty
> > > > return ST->hasPOPCNT() ? TTI::PSK_FastHardware : TTI::PSK_Software;
> > > > }
> > > >
> > > > +llvm::Optional<unsigned> X86TTIImpl::getCacheSize(
> > > > + TargetTransformInfo::CacheLevel Level) const {
> > > > + switch (Level) {
> > > > + case TargetTransformInfo::CacheLevel::L1D:
> > > > + // - Penry
> > > > + // - Nehalem
> > > > + // - Westmere
> > > > + // - Sandy Bridge
> > > > + // - Ivy Bridge
> > > > + // - Haswell
> > > > + // - Broadwell
> > > > + // - Skylake
> > > > + // - Kabylake
> > > > + return 32 * 1024; // 32 KByte
> > > > + case TargetTransformInfo::CacheLevel::L2D:
> > > > + // - Penry
> > > > + // - Nehalem
> > > > + // - Westmere
> > > > + // - Sandy Bridge
> > > > + // - Ivy Bridge
> > > > + // - Haswell
> > > > + // - Broadwell
> > > > + // - Skylake
> > > > + // - Kabylake
> > > > + return 256 * 1024; // 256 KByte
> > > > + }
> > > > +
> > > > + llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
> > > > +}
> > > > +
> > > > +llvm::Optional<unsigned> X86TTIImpl::getCacheAssociativity(
> > > > + TargetTransformInfo::CacheLevel Level) const {
> > > > + // - Penry
> > > > + // - Nehalem
> > > > + // - Westmere
> > > > + // - Sandy Bridge
> > > > + // - Ivy Bridge
> > > > + // - Haswell
> > > > + // - Broadwell
> > > > + // - Skylake
> > > > + // - Kabylake
> > > > + switch (Level) {
> > > > + case TargetTransformInfo::CacheLevel::L1D:
> > > > + LLVM_FALLTHROUGH;
> > > > + case TargetTransformInfo::CacheLevel::L2D:
> > > > + return 8;
> > > > + }
> > > > +
> > > > + llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
> > > > +}
> > > > +
> > > > unsigned X86TTIImpl::getNumberOfRegisters(bool Vector) {
> > > > if (Vector && !ST->hasSSE1())
> > > > return 0;
> > > >
> > > > Modified: llvm/trunk/lib/Target/X86/X86TargetTransformInfo.h
> > > > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/
> > > > X86/X86TargetTransformInfo.h?rev=311647&r1=311646&r2=311647&view=diff
> > > > ============================================================
> > > > ==================
> > > > --- llvm/trunk/lib/Target/X86/X86TargetTransformInfo.h (original)
> > > > +++ llvm/trunk/lib/Target/X86/X86TargetTransformInfo.h Thu Aug 24
> > > > 02:46:25 2017
> > > > @@ -47,6 +47,14 @@ public:
> > > >
> > > > /// @}
> > > >
> > > > + /// \name Cache TTI Implementation
> > > > + /// @{
> > > > + llvm::Optional<unsigned> getCacheSize(
> > > > + TargetTransformInfo::CacheLevel Level) const;
> > > > + llvm::Optional<unsigned> getCacheAssociativity(
> > > > + TargetTransformInfo::CacheLevel Level) const;
> > > > + /// @}
> > > > +
> > > > /// \name Vector TTI Implementations
> > > > /// @{
> > > >
> > > >
> > > >
> > > > _______________________________________________
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