diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp | 15 | ||||
| -rw-r--r-- | llvm/test/Transforms/SimplifyLibCalls/memcmp.ll | 4 |
2 files changed, 15 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp index 575c93b9dd3..ecca3c73b90 100644 --- a/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp +++ b/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp @@ -955,6 +955,17 @@ struct MemCmpOpt : public LibCallOptimization { return B.CreateZExt(B.CreateXor(LHSV, RHSV, "shortdiff"), CI->getType()); } + // Constant folding: memcmp(x, y, l) -> cnst (all arguments are constant) + std::string LHSStr, RHSStr; + if (GetConstantStringInfo(LHS, LHSStr) && + GetConstantStringInfo(RHS, RHSStr)) { + // Make sure we're not reading out-of-bounds memory. + if (Len > LHSStr.length() || Len > RHSStr.length()) + return 0; + uint64_t Ret = memcmp(LHSStr.data(), RHSStr.data(), Len); + return ConstantInt::get(CI->getType(), Ret); + } + return 0; } }; @@ -2479,10 +2490,6 @@ bool SimplifyLibCalls::doInitialization(Module &M) { // lround, lroundf, lroundl: // * lround(cnst) -> cnst' // -// memcmp: -// * memcmp(x,y,l) -> cnst -// (if all arguments are constant and strlen(x) <= l and strlen(y) <= l) -// // pow, powf, powl: // * pow(exp(x),y) -> exp(x*y) // * pow(sqrt(x),y) -> pow(x,y*0.5) diff --git a/llvm/test/Transforms/SimplifyLibCalls/memcmp.ll b/llvm/test/Transforms/SimplifyLibCalls/memcmp.ll index 700873627ec..ed7bcac467d 100644 --- a/llvm/test/Transforms/SimplifyLibCalls/memcmp.ll +++ b/llvm/test/Transforms/SimplifyLibCalls/memcmp.ll @@ -17,6 +17,10 @@ define void @test(i8* %P, i8* %Q, i32 %N, i32* %IP, i1* %BP) { %D = call i32 @memcmp( i8* %P, i8* %Q, i32 2 ) ; <i32> [#uses=1] %E = icmp eq i32 %D, 0 ; <i1> [#uses=1] volatile store i1 %E, i1* %BP + %F = call i32 @memcmp(i8* getelementptr ([4 x i8]* @hel, i32 0, i32 0), + i8* getelementptr ([8 x i8]* @hello_u, i32 0, i32 0), + i32 3) + volatile store i32 %F, i32* %IP ret void } |
