[llvm-dev] vrp (original) (raw)
Davide Italiano via llvm-dev llvm-dev at lists.llvm.org
Mon Aug 7 02:34:45 PDT 2017
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On Mon, Aug 7, 2017 at 2:14 AM, Anastasiya Ruzhanskaya via llvm-dev <llvm-dev at lists.llvm.org> wrote:
I am trying to print it like this (maybe here is smth wrong?)
LazyValueInfo &LV = getAnalysis().getLVI(); DominatorTree &DT = getAnalysis().getDomTree(); LV.printLVI(F, DT, llvm::outs());
The value analysis in llvm is lazy (hence, LVI), so you're trying to print an empty cache, I guess.
for (BasicBlock &BB : F) { for (Instruction &I : BB) { if (Value* v = dyncast(&I)) if (v->getType()->isIntegerTy()) { ConstantRange r = LV.getConstantRange(v, &BB, &I); I.dump(); printf("LOWER VALUE : %llu\n",r.getLower().getRawData()); printf("UPPER VALUE : %llu\n",r.getUpper().getRawData()); } }
About your other question, "the value range pass was not able to determine any size, even of the induction variable, is it a correct behavior?". Yes, returning a conservative answer is always correct, but not optimal.
As reference, a more sophisticated range analysis finds the following ranges for your IR:
[0, +inf] %i.03 = phi i32 [ 0, %entry ], [ %inc, %for.body ] [0, +inf] %s.02 = phi i32 [ 0, %entry ], [ %add2, %for.body ] [0, +inf] %j.01 = phi i32 [ 0, %entry ], [ %add1, %for.body ] [0, +inf] %add = add nsw i32 %j.01, %i.03 [1, +inf] %add1 = add nsw i32 %add, 1 [1, +inf] %add2 = add nsw i32 %s.02, %add1 [1, +inf] %inc = add nsw i32 %i.03, 1 [2, +inf] %add3 = add nsw i32 %add2, %add1
-- Davide
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