Hi,
everytime one has to add instruction at the beginning of a basic block, one
has to skip past PHI nodes that are already there. How about adding a new
method to BasicBlock, to get that first non-PHI instruction? So, adding an
instruction will be as simple as:
new SomeInstruction(............., BB->getFirstNonPHI())
Patch attached. Comments?
- Volodya
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On Sun, 4 Jun 2006, Vladimir Prus wrote:> everytime one has to add instruction at the beginning of a basic block, one > has to skip past PHI nodes that are already there. How about adding a new > method to BasicBlock, to get that first non-PHI instruction? So, adding an > instruction will be as simple as: > > new SomeInstruction(............., BB->getFirstNonPHI())Sure, sounds good. A couple requests: 1. Please add a const version that returns a const Instruction* also. 2. There is no need to check for running off the end of the basic block, you are guaranteed that a block has a terminator, which is not a PHI. -Chris -- http://nondot.org/sabre/ http://llvm.org/
Chris Lattner wrote:> On Sun, 4 Jun 2006, Vladimir Prus wrote: > >> everytime one has to add instruction at the beginning of a basic >> block, one >> has to skip past PHI nodes that are already there. How about adding a new >> method to BasicBlock, to get that first non-PHI instruction? So, >> adding an >> instruction will be as simple as: >> >> new SomeInstruction(............., BB->getFirstNonPHI()) > > 2. There is no need to check for running off the end of the basic block, > you are guaranteed that a block has a terminator, which is not a PHI.Assuming it's a valid BasicBlock. Which, if I understand correctly, isn't always true in mid-transformation. Perhaps you should turn it into an assert instead, to minimize surprises? I can't check if this actually happens with llvm.org seemingly down, but I do recall a situation like that. Maybe it was the BB list within a function? Nick
Chris Lattner wrote:> On Sun, 4 Jun 2006, Vladimir Prus wrote: >> everytime one has to add instruction at the beginning of a basic block, >> one has to skip past PHI nodes that are already there. How about adding a >> new method to BasicBlock, to get that first non-PHI instruction? So, >> adding an instruction will be as simple as: >> >> new SomeInstruction(............., BB->getFirstNonPHI()) > > Sure, sounds good. A couple requests: > > 1. Please add a const version that returns a const Instruction* also.I was considering it, but then decided that given that you can't pass 'const Instruction*' as 'insert before' parameter of any other instruction, there's no point in adding it. Maybe, the method should be Instruction* getFirstNonPHI() const ? Given that in C++ constness is generally not deep -- i.e. don't apply to contained objects. - Volodya