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Allow GVN to hack on memcpy's, making them open to further optimization.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46693 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -19,6 +19,7 @@
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Instructions.h"
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#include "llvm/Value.h"
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#include "llvm/ADT/BitVector.h"
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@ -736,6 +737,7 @@ namespace {
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SmallVector<Instruction*, 4>& toErase);
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bool processNonLocalLoad(LoadInst* L,
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SmallVector<Instruction*, 4>& toErase);
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bool processMemCpy(MemCpyInst* M, SmallVector<Instruction*, 4>& toErase);
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Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig,
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DenseMap<BasicBlock*, Value*> &Phis,
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bool top_level = false);
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@ -1017,6 +1019,84 @@ bool GVN::processLoad(LoadInst* L,
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return deletedLoad;
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}
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/// processMemCpy - perform simplication of memcpy's. If we have memcpy A which
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/// copies X to Y, and memcpy B which copies Y to Z, then we can rewrite B to be
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/// a memcpy from X to Z (or potentially a memmove, depending on circumstances).
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/// This allows later passes to remove the first memcpy altogether.
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bool GVN::processMemCpy(MemCpyInst* M,
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SmallVector<Instruction*, 4>& toErase) {
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MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
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// First, we have to check that the dependency is another memcpy
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Instruction* dep = MD.getDependency(M);
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if (dep == MemoryDependenceAnalysis::None ||
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dep == MemoryDependenceAnalysis::NonLocal ||
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!isa<MemCpyInst>(dep))
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return false;
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// We can only transforms memcpy's where the dest of one is the source of the
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// other
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MemCpyInst* MDep = cast<MemCpyInst>(dep);
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if (M->getSource() != MDep->getDest())
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return false;
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// Second, the length of the memcpy's must be the same, or the preceeding one
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// must be larger than the following one.
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Value* DepLength = MDep->getLength();
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uint64_t CpySize = ~0UL;
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uint64_t DepSize = ~0UL;
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if (isa<ConstantInt>(DepLength)) {
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if (isa<ConstantInt>(M->getLength())) {
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if (cast<ConstantInt>(DepLength)->getLimitedValue() <
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cast<ConstantInt>(M->getLength())->getLimitedValue()) {
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return false;
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} else {
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CpySize = cast<ConstantInt>(M->getLength())->getLimitedValue();
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DepSize = cast<ConstantInt>(DepLength)->getLimitedValue();
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}
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} else {
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return false;
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}
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} else {
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return false;
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}
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// Finally, we have to make sure that the dest of the second does not
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// alias the source of the first
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AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
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if (AA.alias(M->getRawDest(), CpySize, MDep->getRawSource(), DepSize) !=
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AliasAnalysis::NoAlias) {
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// If they don't, we can still make the transformation by first turning M
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// into a memmove rather than a memcpy.
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bool is32bit = M->getIntrinsicID() == Intrinsic::memcpy_i32;
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Function* MemMoveFun = Intrinsic::getDeclaration(
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M->getParent()->getParent()->getParent(),
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is32bit ? Intrinsic::memmove_i32 :
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Intrinsic::memmove_i64);
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std::vector<Value*> args;
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args.push_back(M->getRawDest());
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args.push_back(MDep->getRawSource());
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args.push_back(M->getLength());
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args.push_back(M->getAlignment());
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new CallInst(MemMoveFun, args.begin(), args.end(), "", M);
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MD.removeInstruction(M);
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toErase.push_back(M);
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return true;
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}
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// If all checks passed, then we can transform these memcpy's
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M->setSource(MDep->getRawSource());
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// Reset dependence information for the memcpy
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MD.removeInstruction(M);
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return true;
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}
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/// processInstruction - When calculating availability, handle an instruction
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/// by inserting it into the appropriate sets
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bool GVN::processInstruction(Instruction* I,
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@ -1025,6 +1105,8 @@ bool GVN::processInstruction(Instruction* I,
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SmallVector<Instruction*, 4>& toErase) {
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if (LoadInst* L = dyn_cast<LoadInst>(I)) {
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return processLoad(L, lastSeenLoad, toErase);
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} else if (MemCpyInst* M = dyn_cast<MemCpyInst>(I)) {
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return processMemCpy(M, toErase);
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}
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unsigned num = VN.lookup_or_add(I);
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22
test/Transforms/GVN/memcpy.ll
Normal file
22
test/Transforms/GVN/memcpy.ll
Normal file
@ -0,0 +1,22 @@
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; RUN: llvm-as < %s | opt -gvn -dse | llvm-dis | not grep {i8* %agg.result21, i8* %tmp219}
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
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target triple = "i686-apple-darwin9"
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define void @ccosl({ x86_fp80, x86_fp80 }* sret %agg.result, x86_fp80 %z.0, x86_fp80 %z.1) nounwind {
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entry:
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%tmp2 = alloca { x86_fp80, x86_fp80 } ; <{ x86_fp80, x86_fp80 }*> [#uses=1]
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%memtmp = alloca { x86_fp80, x86_fp80 }, align 16 ; <{ x86_fp80, x86_fp80 }*> [#uses=2]
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%tmp5 = sub x86_fp80 0xK80000000000000000000, %z.1 ; <x86_fp80> [#uses=1]
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call void @ccoshl( { x86_fp80, x86_fp80 }* sret %memtmp, x86_fp80 %tmp5, x86_fp80 %z.0 ) nounwind
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%tmp219 = bitcast { x86_fp80, x86_fp80 }* %tmp2 to i8* ; <i8*> [#uses=2]
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%memtmp20 = bitcast { x86_fp80, x86_fp80 }* %memtmp to i8* ; <i8*> [#uses=1]
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call void @llvm.memcpy.i32( i8* %tmp219, i8* %memtmp20, i32 32, i32 16 )
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%agg.result21 = bitcast { x86_fp80, x86_fp80 }* %agg.result to i8* ; <i8*> [#uses=1]
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call void @llvm.memcpy.i32( i8* %agg.result21, i8* %tmp219, i32 32, i32 16 )
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ret void
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}
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declare void @ccoshl({ x86_fp80, x86_fp80 }* sret , x86_fp80, x86_fp80) nounwind
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declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind
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