similar to: [LLVMdev] converting an unconditional into a conditional branch

Dear LLVM developers, I have a question regarding the IPSCCP class and the handling of dead blocks: The file lib/Transforms/Scalar/SCCP.cpp of llvm 2.8 from contains some code to deal with a dead block which could not be folded (line 1909ff). This happens when a user of this dead block is a branch or switch with an undef condition. The action taken than is to replace this terminator with an

This email is related with the code of commit: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20120409/140650.html. This commit will let our unconditional branch instruction not be deleted when its successor is the nature layout and its basic block's instruction only one instruction. However, I have some concerns about it, especially in the debug mode. Let me show you some

Dear All I'm making a transformation pass that inserts a new basic block at the start of a loop. However when I try to change predecessor/successor relations, it does not consider the new block in the loop at all. So I got that just inserting a loop in a function before another loop is not enough. So how exactly to do this job? Regards, Marwa Yusuf Teaching Assistant - Computer Engineering

John, you are right. I 'browsed' the doxygen's inheritance diagram. Shouldn't I then be able to cast Constant * to Value*? Plugging the retrieved Constant* (from ConstantExpr::getGetElementPtr) into Instruction->setOperand compiles, but gives me an assertion failure at runtime. I have no access to the code at the moment. I will gather more information possibly tomorrow.

> On Mar 20, 2020, at 12:34 PM, Nicholas Krause <xerofoify at gmail.com> wrote: > >> >> The problem isn’t constants or functions themselves, it is that they are instances of llvm::Value. Everything that walks a use/def list would have to run code that checks for this, and every call to inst->setOperand() would have to do locking or conditional locking. This would be

> On Mar 19, 2020, at 2:31 PM, Johannes Doerfert <johannesdoerfert at gmail.com> wrote: > > I think addressing this issue first makes sense. I would however start > by determining the actual impact of different design choices here. I > mean, do we know locks will be heavily contented? If I had to guess I'd > say most passes will not create or modify functions nor add

Hi all, Somewhat of a newbie's question, hope you can help me out. I'm trying to turn unconditional BranchInst's into conditional ones (with a condition I'm supplying) branching between the original target and a basic block of my choice. Apparently the way to do that is to create a new conditional BranchInst and remove the unconditional one from its basic block. However when

Hi all, extracting datafields of globals, the API code ends up in a Constant * Constant* const_ptr_103 = ConstantExpr::getGetElementPtr(gvar_struct_foo, const_ptr_103_indices); it can be used to initialize e.g. a new instruction like: StoreInst* void_119 = new StoreInst(const_float_102, const_ptr_103, false, label_entry_113); But how about replacing the operand of an already existing

Sorry for the confusion, I pasted the code I fixed locally... Here is the code at top of the trunk: // load (select (cond, null, P)) -> load P if (Constant *C = dyn_cast<Constant>(SI->getOperand(1))) if (C->isNullValue()) { LI.setOperand(0, SI->getOperand(2)); return &LI; } So it is a bug? -----Original Message----- From:

Hi all, I've been investigating a machine verifier failure on the attached testcase, and I'm tempted to say the verifier is wrong and should accept it. Skip the description for the proposed change. On AArch64, the verifier complains with: *** Bad machine code: MBB exits via unconditional branch but doesn't have exactly one CFG successor! *** - function: t4 - basic

Hi. Thanks. I changed the code but the problem exists. This is my new code which is again very simple: ... bool runOnFunction(Function &F) override { vector<Instruction *> dels; dels.clear(); for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) { Instruction *I = &*(It++); if (auto* op = dyn_cast<BinaryOperator>(I)) { IRBuilder<NoFolder>

The code is really simple. But I can not the reason for the segmentation fault. I only know that the eraseFromParent() function leads to it. The whole code is: ... bool runOnFunction(Function &F) override { for (auto &I : instructions(F)) { if (auto* op = dyn_cast<BinaryOperator>(&I)) { IRBuilder<> builder(op); Value* lhs = op->getOperand(0); Value* rhs =

On Feb 1, 2011, at 1:08 PM, Andrew Clinton wrote: > I have a (non-entry) basic block that contains only PHI nodes and an > unconditional branch (that does not branch to itself). Is it always > possible to merge this block with it's successor and produce a > semantically equivalent program? I'm trying to undo some of the loop > optimizations that LLVM has applied to my

Hi, I would like to understand better the meaning of constant null pointer in LLVM IR. Can the optimizer assume that dereferencing a null pointer is always unreachable? Or is it only the case for address space 0? Is it ok to have null pointer be a valid pointer for an address space other than 0? In InstCombine pass in InstCombiner::visitLoadInst(LoadInst &LI) I see that we replace load of

Hi. This is part of my code: ... if (auto* op = dyn_cast<BinaryOperator>(&I)) { Value* lhs = op->getOperand(0); Value* rhs = op->getOperand(1); Value* mul = builder.CreateMul(lhs, rhs); for (auto& U : op->uses()) { User* user = U.getUser(); user->setOperand(U.getOperandNo(), mul); } I.eraseFromParent(); } ... This leads to the following

Hello, I need to append something to the global "llvm.global_ctors". This variable may or may not already be declared within the current module. If I lookup the global variable, I see that it supports a getOperand(i) and setOperand(i,c), but does not support any way that I can enlarge that array to add a new record. Any suggestions? -- Nick Johnson

I have a MDNode, and one of its operand is an int. I'd like to assign a new int value to that operand during the llvm optimization. What is the right way to do this ? (There is no setOperand() with MDNode class.) Junjie

Hi all. Is it allowed to modify ConstantArray object within setOperand method, or it is better to leave old ConstantArray object and create new one? Thanks! -Stepan.

Hi all, I am trying to merge functions with the same debug location by using replaceAllUsesWith(). However, this leads to type unmatched problems because the functions with the same debug location can have different parameters. An example is foo(struct A) can be compiled to foo.1(struct A.1) and foo.2(struct A.2). I have inserted CastInst to solve the problems of arguments and return values type

Hello, I am trying to reset the operands of instructions. What I am doing is, I am finding all Uses of a specific operand in an Instruction and resetting it with a new value using "setOperands(int, Value*)". I am doing as: for (auto vmitr=vm.begin(), vsitr=vs.begin(); vmitr!=vm.end() && vsitr!=vs.end(); vmitr++, vsitr++){ // I have two *Value ( operands) for ( auto myitr