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Fix several nasty bugs in the strchr optimizer, this fixes
SimplifyLibCalls/2007-04-06-strchr-miscompile.ll and PR1307 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35706 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -532,74 +532,80 @@ public:
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"Number of 'strchr' calls simplified") {}
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/// @brief Make sure that the "strchr" function has the right prototype
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virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC){
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if (f->getReturnType() == PointerType::get(Type::Int8Ty) &&
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f->arg_size() == 2)
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return true;
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return false;
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virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
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const FunctionType *FT = F->getFunctionType();
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return FT->getNumParams() == 2 &&
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FT->getReturnType() == PointerType::get(Type::Int8Ty) &&
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FT->getParamType(0) == FT->getReturnType() &&
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isa<IntegerType>(FT->getParamType(1));
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}
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/// @brief Perform the strchr optimizations
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virtual bool OptimizeCall(CallInst *ci, SimplifyLibCalls &SLC) {
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// If there aren't three operands, bail
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if (ci->getNumOperands() != 3)
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return false;
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virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
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// Check that the first argument to strchr is a constant array of sbyte.
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// If it is, get the length and data, otherwise return false.
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uint64_t len, StartIdx;
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ConstantArray* CA = 0;
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if (!GetConstantStringInfo(ci->getOperand(1), CA, len, StartIdx))
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uint64_t StrLength, StartIdx;
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ConstantArray *CA = 0;
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if (!GetConstantStringInfo(CI->getOperand(1), CA, StrLength, StartIdx))
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return false;
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// Check that the second argument to strchr is a constant int. If it isn't
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// a constant integer, we can try an alternate optimization
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ConstantInt* CSI = dyn_cast<ConstantInt>(ci->getOperand(2));
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// If the second operand is not constant, just lower this to memchr since we
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// know the length of the input string.
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ConstantInt *CSI = dyn_cast<ConstantInt>(CI->getOperand(2));
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if (!CSI) {
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// The second operand is not constant just lower this to
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// memchr since we know the length of the string since it is constant.
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Constant *f = SLC.get_memchr();
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Value* args[3] = {
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ci->getOperand(1),
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ci->getOperand(2),
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ConstantInt::get(SLC.getIntPtrType(), len)
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Value *Args[3] = {
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CI->getOperand(1),
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CI->getOperand(2),
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ConstantInt::get(SLC.getIntPtrType(), StrLength+1)
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};
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ci->replaceAllUsesWith(new CallInst(f, args, 3, ci->getName(), ci));
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ci->eraseFromParent();
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CI->replaceAllUsesWith(new CallInst(SLC.get_memchr(), Args, 3,
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CI->getName(), CI));
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CI->eraseFromParent();
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return true;
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}
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// Get the character we're looking for
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int64_t chr = CSI->getSExtValue();
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int64_t CharValue = CSI->getSExtValue();
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if (StrLength == 0) {
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// If the length of the string is zero, and we are searching for zero,
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// return the input pointer.
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if (CharValue == 0) {
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CI->replaceAllUsesWith(CI->getOperand(1));
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} else {
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// Otherwise, char wasn't found.
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CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
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}
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CI->eraseFromParent();
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return true;
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}
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// Compute the offset
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uint64_t offset = 0;
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bool char_found = false;
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for (uint64_t i = 0; i < len; ++i) {
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if (ConstantInt* CI = dyn_cast<ConstantInt>(CA->getOperand(i))) {
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// Check for the null terminator
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if (CI->isZero())
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break; // we found end of string
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else if (CI->getSExtValue() == chr) {
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char_found = true;
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offset = i;
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uint64_t i = 0;
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while (1) {
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assert(i <= StrLength && "Didn't find null terminator?");
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if (ConstantInt *C = dyn_cast<ConstantInt>(CA->getOperand(i+StartIdx))) {
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// Did we find our match?
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if (C->getSExtValue() == CharValue)
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break;
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if (C->isZero()) {
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// We found the end of the string. strchr returns null.
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CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
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CI->eraseFromParent();
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return true;
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}
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}
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++i;
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}
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// strchr(s,c) -> offset_of_in(c,s)
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// strchr(s+n,c) -> gep(s+n+i,c)
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// (if c is a constant integer and s is a constant string)
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if (char_found) {
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Value* Idx = ConstantInt::get(Type::Int64Ty,offset);
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GetElementPtrInst* GEP = new GetElementPtrInst(ci->getOperand(1), Idx,
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ci->getOperand(1)->getName()+".strchr",ci);
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ci->replaceAllUsesWith(GEP);
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} else {
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ci->replaceAllUsesWith(
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ConstantPointerNull::get(PointerType::get(Type::Int8Ty)));
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}
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ci->eraseFromParent();
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Value *Idx = ConstantInt::get(Type::Int64Ty, i);
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Value *GEP = new GetElementPtrInst(CI->getOperand(1), Idx,
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CI->getOperand(1)->getName() +
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".strchr", CI);
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CI->replaceAllUsesWith(GEP);
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CI->eraseFromParent();
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return true;
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}
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} StrChrOptimizer;
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