[Beignet] [PATCH V2 3/3] add local copy propagation optimization for each basic block
Zhigang Gong
zhigang.gong at linux.intel.com
Wed Sep 23 18:13:39 PDT 2015
On Fri, Sep 11, 2015 at 08:50:49AM +0800, Guo Yejun wrote:
> It is done at selection ir level, it removes MOV instructions
> and helps to reduce the register pressure.
>
> For instructions like:
> MOV(8) %42<2>:UB : %53<32,8,4>:UB
> ADD(8) %43<2>:B : %40<16,8,2>:B -%42<16,8,2>:B
> can be optimized as:
> ADD(8) %43<2>:UB : %56<32,8,4>:UB -%53<32,8,4>:UB
>
> Signed-off-by: Guo Yejun <yejun.guo at intel.com>
> ---
> backend/src/backend/gen_insn_selection.cpp | 4 +
> backend/src/backend/gen_insn_selection.hpp | 2 +
> .../src/backend/gen_insn_selection_optimize.cpp | 201 ++++++++++++++++++++-
> 3 files changed, 202 insertions(+), 5 deletions(-)
>
> diff --git a/backend/src/backend/gen_insn_selection.cpp b/backend/src/backend/gen_insn_selection.cpp
> index 28c7ed2..038b839 100644
> --- a/backend/src/backend/gen_insn_selection.cpp
> +++ b/backend/src/backend/gen_insn_selection.cpp
> @@ -2062,6 +2062,10 @@ namespace gbe
> ///////////////////////////////////////////////////////////////////////////
> // Code selection public implementation
> ///////////////////////////////////////////////////////////////////////////
> + const GenContext& Selection::getCtx()
> + {
> + return this->opaque->ctx;
> + }
>
> Selection::Selection(GenContext &ctx) {
> this->blockList = NULL;
> diff --git a/backend/src/backend/gen_insn_selection.hpp b/backend/src/backend/gen_insn_selection.hpp
> index 86542b0..275eb9c 100644
> --- a/backend/src/backend/gen_insn_selection.hpp
> +++ b/backend/src/backend/gen_insn_selection.hpp
> @@ -271,6 +271,8 @@ namespace gbe
> void optimize(void);
> uint32_t opt_features;
>
> + const GenContext &getCtx();
> +
> /*! Use custom allocators */
> GBE_CLASS(Selection);
> };
> diff --git a/backend/src/backend/gen_insn_selection_optimize.cpp b/backend/src/backend/gen_insn_selection_optimize.cpp
> index c82fbe5..1c2f559 100644
> --- a/backend/src/backend/gen_insn_selection_optimize.cpp
> +++ b/backend/src/backend/gen_insn_selection_optimize.cpp
> @@ -12,38 +12,229 @@
>
> namespace gbe
> {
> + //helper functions
> + static uint32_t CalculateElements(const GenRegister& reg, uint32_t execWidth)
> + {
> + uint32_t elements = 0;
> + uint32_t elementSize = typeSize(reg.type);
> + uint32_t width = GenRegister::width_size(reg);
> + assert(execWidth >= width);
> + uint32_t height = execWidth / width;
> + uint32_t vstride = GenRegister::vstride_size(reg);
> + uint32_t hstride = GenRegister::hstride_size(reg);
> + uint32_t base = reg.subnr;
> + for (uint32_t i = 0; i < height; ++i) {
> + uint32_t offsetInByte = base;
> + for (uint32_t j = 0; j < width; ++j) {
> + uint32_t offsetInType = offsetInByte / elementSize;
> + elements |= (1 << offsetInType);
> + offsetInByte += hstride * elementSize;
> + }
> + offsetInByte += vstride * elementSize;
> + }
> + return elements;
> + }
>
> class SelOptimizer
> {
> public:
> - SelOptimizer(uint32_t features) : features(features) {}
> + SelOptimizer(const GenContext& ctx, uint32_t features) : ctx(ctx), features(features) {}
> virtual void run() = 0;
> virtual ~SelOptimizer() {}
> protected:
> + const GenContext &ctx; //in case that we need it
> uint32_t features;
> };
>
> class SelBasicBlockOptimizer : public SelOptimizer
> {
> public:
> - SelBasicBlockOptimizer(uint32_t features, SelectionBlock &bb) : SelOptimizer(features), bb(bb) {}
> + SelBasicBlockOptimizer(const GenContext& ctx,
> + const ir::Liveness::LiveOut& liveout,
> + uint32_t features,
> + SelectionBlock &bb) :
> + SelOptimizer(ctx, features), bb(bb), liveout(liveout), optimized(false)
> + {
> + }
> ~SelBasicBlockOptimizer() {}
> virtual void run();
>
> private:
> + // local copy propagation
> + class ReplaceInfo
> + {
> + public:
> + ReplaceInfo(SelectionInstruction& insn,
> + const GenRegister& intermedia,
> + const GenRegister& replacement,
> + uint32_t execWidth) :
> + insn(insn), intermedia(intermedia), replacement(replacement)
> + {
> + assert(insn.opcode == SEL_OP_MOV);
> + assert(&(insn.src(0)) == &replacement);
> + assert(&(insn.dst(0)) == &intermedia);
> + this->elements = CalculateElements(intermedia, execWidth);
> + replacementChanged = false;
> + }
> + ~ReplaceInfo()
> + {
> + this->toBeReplacements.clear();
> + }
> +
> + SelectionInstruction& insn;
> + const GenRegister& intermedia;
> + uint32_t elements;
> + const GenRegister& replacement;
> + set<GenRegister*> toBeReplacements;
> + bool replacementChanged;
> + GBE_CLASS(ReplaceInfo);
> + };
> + set<ReplaceInfo*> replaceInfos;
> + void doLocalCopyPropagation();
> + void addToReplaceInfos(SelectionInstruction& insn);
> + void changeInsideReplaceInfos(const SelectionInstruction& insn, GenRegister& var);
> + void removeFromReplaceInfos(const GenRegister& var);
> + void doReplacement(ReplaceInfo* info);
> + void cleanReplaceInfos();
> + static void propagateRegister(GenRegister& dst, const GenRegister& src);
> +
> SelectionBlock &bb;
> - static const size_t MaxTries = 1; //the times for optimization
> + const ir::Liveness::LiveOut& liveout;
> + bool optimized;
> + static const size_t MaxTries = 1; //the max times of optimization try
> };
>
> + void SelBasicBlockOptimizer::propagateRegister(GenRegister& dst, const GenRegister& src)
This function looks much like a GenRegister static method, because it doesn't reference any
external information.
> + {
> + dst.type = src.type;
> + dst.file = src.file;
> + dst.physical = src.physical;
> + dst.subphysical = src.subphysical;
> + dst.value.reg = src.value.reg;
> + dst.vstride = src.vstride;
> + dst.width = src.width;
> + dst.hstride = src.hstride;
> + dst.quarter = src.quarter;
> + dst.nr = src.nr;
> + dst.subnr = src.subnr;
> + dst.address_mode = src.address_mode;
> + dst.a0_subnr = src.a0_subnr;
> + dst.addr_imm = src.addr_imm;
> +
> + dst.negation = dst.negation ^ src.negation;
> + dst.absolute = dst.absolute | src.absolute;
> + }
> +
> + void SelBasicBlockOptimizer::doReplacement(ReplaceInfo* info)
> + {
> + for (GenRegister* reg : info->toBeReplacements) {
> + propagateRegister(*reg, info->replacement);
> + }
> + bb.insnList.erase(&(info->insn));
> + }
> +
> + void SelBasicBlockOptimizer::cleanReplaceInfos()
> + {
> + for (ReplaceInfo* info : replaceInfos) {
> + doReplacement(info);
> + delete info;
> + }
> + replaceInfos.clear();
> + }
> +
> + void SelBasicBlockOptimizer::removeFromReplaceInfos(const GenRegister& var)
> + {
> + for (set<ReplaceInfo*>::iterator pos = replaceInfos.begin(); pos != replaceInfos.end(); ) {
> + ReplaceInfo* info = *pos;
> + if (info->intermedia.reg() == var.reg()) {
> + if (info->intermedia.quarter == var.quarter && info->intermedia.subnr == var.subnr)
> + doReplacement(info);
> + replaceInfos.erase(pos++);
> + delete info;
> + }
> + else if (info->replacement.reg() == var.reg()) {
> + info->replacementChanged = true;
> + ++pos;
> + }
> + else
> + ++pos;
> + }
> + }
> +
> + void SelBasicBlockOptimizer::addToReplaceInfos(SelectionInstruction& insn)
> + {
> + assert(insn.opcode == SEL_OP_MOV);
> + const GenRegister& src = insn.src(0);
> + const GenRegister& dst = insn.dst(0);
> + if (src.type != dst.type || src.file != dst.file)
> + return;
> +
> + if (liveout.find(dst.reg()) != liveout.end())
> + return;
> +
> + ReplaceInfo* info = new ReplaceInfo(insn, dst, src, insn.state.execWidth);
> + replaceInfos.insert(info);
> + }
> +
> + void SelBasicBlockOptimizer::changeInsideReplaceInfos(const SelectionInstruction& insn, GenRegister& var)
> + {
> + for (ReplaceInfo* info : replaceInfos) {
> + if (info->intermedia.reg() == var.reg()) {
> + bool replaceable = false;
It's better to add a comment here to describe the cases which can't be replaced and why.
> + if (insn.opcode != SEL_OP_BSWAP && !insn.isWrite()) {
> + if (!info->replacementChanged && info->intermedia.type == var.type && info->intermedia.quarter == var.quarter && info->intermedia.subnr == var.subnr) {
> + uint32_t elements = CalculateElements(var, insn.state.execWidth);
> + if (info->elements == elements) {
Why not compare each attribute value, such as vstride_size,hstride_size,.....?
The other parts LGTM,
Thanks,
Zhigang Gong
> + info->toBeReplacements.insert(&var);
> + replaceable = true;
> + }
> + }
> + }
> +
> + //if we found the same register, but could not be replaced for some reason,
> + //that means we could not remove MOV instruction, and so no replacement,
> + //so we'll remove the info for this case.
> + if (!replaceable) {
> + replaceInfos.erase(info);
> + delete info;
> + }
> + break;
> + }
> + }
> + }
> +
> + void SelBasicBlockOptimizer::doLocalCopyPropagation()
> + {
> + for (SelectionInstruction &insn : bb.insnList) {
> + for (uint8_t i = 0; i < insn.srcNum; ++i)
> + changeInsideReplaceInfos(insn, insn.src(i));
> +
> + for (uint8_t i = 0; i < insn.dstNum; ++i)
> + removeFromReplaceInfos(insn.dst(i));
> +
> + if (insn.opcode == SEL_OP_MOV)
> + addToReplaceInfos(insn);
> + }
> + cleanReplaceInfos();
> + }
> +
> void SelBasicBlockOptimizer::run()
> {
> + for (size_t i = 0; i < MaxTries; ++i) {
> + optimized = false;
>
> + doLocalCopyPropagation();
> + //doOtherLocalOptimization();
> +
> + if (!optimized)
> + break; //break since no optimization found at this round
> + }
> }
>
> class SelGlobalOptimizer : public SelOptimizer
> {
> public:
> - SelGlobalOptimizer(uint32_t features) : SelOptimizer(features) {}
> + SelGlobalOptimizer(const GenContext& ctx, uint32_t features) : SelOptimizer(ctx, features) {}
> ~SelGlobalOptimizer() {}
> virtual void run();
> };
> @@ -57,7 +248,7 @@ namespace gbe
> {
> //do basic block level optimization
> for (SelectionBlock &block : *blockList) {
> - SelBasicBlockOptimizer bbopt(opt_features, block);
> + SelBasicBlockOptimizer bbopt(getCtx(), getCtx().getLiveOut(block.bb), opt_features, block);
> bbopt.run();
> }
>
> --
> 1.9.1
>
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