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author | Meador Inge <meadori@codesourcery.com> | 2012-11-11 05:11:20 +0000 |
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committer | Meador Inge <meadori@codesourcery.com> | 2012-11-11 05:11:20 +0000 |
commit | bb51ec8b62c2819882b82a2510bf4df6f459bd51 (patch) | |
tree | df5b7dc662ea28fb25dd4030a6fec6ac8659af08 /lib/Transforms/Utils/SimplifyLibCalls.cpp | |
parent | 6e1591a5d5fba3bde66e3ffd4dd73edd6b94cecf (diff) | |
download | llvm-bb51ec8b62c2819882b82a2510bf4df6f459bd51.tar.gz llvm-bb51ec8b62c2819882b82a2510bf4df6f459bd51.tar.bz2 llvm-bb51ec8b62c2819882b82a2510bf4df6f459bd51.tar.xz |
instcombine: Migrate memcmp optimizations
This patch migrates the memcmp optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167683 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/Utils/SimplifyLibCalls.cpp')
-rw-r--r-- | lib/Transforms/Utils/SimplifyLibCalls.cpp | 55 |
1 files changed, 53 insertions, 2 deletions
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp index b5ea46dc0d..805fcbe3cb 100644 --- a/lib/Transforms/Utils/SimplifyLibCalls.cpp +++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp @@ -914,6 +914,51 @@ struct StrStrOpt : public LibCallOptimization { } }; +struct MemCmpOpt : public LibCallOptimization { + virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) { + FunctionType *FT = Callee->getFunctionType(); + if (FT->getNumParams() != 3 || !FT->getParamType(0)->isPointerTy() || + !FT->getParamType(1)->isPointerTy() || + !FT->getReturnType()->isIntegerTy(32)) + return 0; + + Value *LHS = CI->getArgOperand(0), *RHS = CI->getArgOperand(1); + + if (LHS == RHS) // memcmp(s,s,x) -> 0 + return Constant::getNullValue(CI->getType()); + + // Make sure we have a constant length. + ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getArgOperand(2)); + if (!LenC) return 0; + uint64_t Len = LenC->getZExtValue(); + + if (Len == 0) // memcmp(s1,s2,0) -> 0 + return Constant::getNullValue(CI->getType()); + + // memcmp(S1,S2,1) -> *(unsigned char*)LHS - *(unsigned char*)RHS + if (Len == 1) { + Value *LHSV = B.CreateZExt(B.CreateLoad(CastToCStr(LHS, B), "lhsc"), + CI->getType(), "lhsv"); + Value *RHSV = B.CreateZExt(B.CreateLoad(CastToCStr(RHS, B), "rhsc"), + CI->getType(), "rhsv"); + return B.CreateSub(LHSV, RHSV, "chardiff"); + } + + // Constant folding: memcmp(x, y, l) -> cnst (all arguments are constant) + StringRef LHSStr, RHSStr; + if (getConstantStringInfo(LHS, LHSStr) && + getConstantStringInfo(RHS, RHSStr)) { + // Make sure we're not reading out-of-bounds memory. + if (Len > LHSStr.size() || Len > RHSStr.size()) + return 0; + uint64_t Ret = memcmp(LHSStr.data(), RHSStr.data(), Len); + return ConstantInt::get(CI->getType(), Ret); + } + + return 0; + } +}; + } // End anonymous namespace. namespace llvm { @@ -932,7 +977,7 @@ class LibCallSimplifierImpl { StpCpyChkOpt StpCpyChk; StrNCpyChkOpt StrNCpyChk; - // String and memory library call optimizations. + // String library call optimizations. StrCatOpt StrCat; StrNCatOpt StrNCat; StrChrOpt StrChr; @@ -949,6 +994,9 @@ class LibCallSimplifierImpl { StrCSpnOpt StrCSpn; StrStrOpt StrStr; + // Memory library call optimizations. + MemCmpOpt MemCmp; + void initOptimizations(); void addOpt(LibFunc::Func F, LibCallOptimization* Opt); public: @@ -972,7 +1020,7 @@ void LibCallSimplifierImpl::initOptimizations() { Optimizations["__strncpy_chk"] = &StrNCpyChk; Optimizations["__stpncpy_chk"] = &StrNCpyChk; - // String and memory library call optimizations. + // String library call optimizations. addOpt(LibFunc::strcat, &StrCat); addOpt(LibFunc::strncat, &StrNCat); addOpt(LibFunc::strchr, &StrChr); @@ -994,6 +1042,9 @@ void LibCallSimplifierImpl::initOptimizations() { addOpt(LibFunc::strspn, &StrSpn); addOpt(LibFunc::strcspn, &StrCSpn); addOpt(LibFunc::strstr, &StrStr); + + // Memory library call optimizations. + addOpt(LibFunc::memcmp, &MemCmp); } Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) { |