CODEWITHSUNDEEP
cllvmintermediate-code
pythonic
pythonic

Reputation: 21665

What is wrong with this LLVM IR code

I have an LLVM IR code that looks something like this.

  %8 = load i64* @tid, align 8
  %arrayidx1 = getelementptr inbounds [16 x i32]* @h, 
    i32 0, i64 %8 ;<-- %8 works fine here
  ..............
  %OldFuncCounter7 = load i64* getelementptr inbounds ([16 x i64]* 
    @EdgeProfCounters, i64 0, i64 %8) ;<-- error here, %8 not allowed
  ..............

In the line where arrayidx1 is assigned, everything is fine, but for OldFuncCounter7, the LLVM compiler complains by saying "invalid use of function-local name". It is due to the %8 I am using. If i replace it with a constant, it works fine. So my question is why is that %8 works fine with arrayidx1, but not with OldFuncCounter7. What is going on here?

The whole basic block where this error occurs is shown below

  %8 = load i64* @tid, align 8
  %arrayidx1 = getelementptr inbounds [16 x i32]* @h, i32 0, i64 %8
  store volatile i32 3, i32* %arrayidx1, align 4
  %9 = load volatile i32* getelementptr inbounds ([16 x i32]* @h, i32 0, i64 0), align 4
  %call2 = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([10 x i8]* @.str, i32 0, i32 0), i32 %9)
  %10 = load i64* @tid, align 8
  store volatile i64 %10, i64* %clock, align 8
  %call3 = call i32 @getpid() nounwind
  %call4 = call i64 @pthread_self() nounwind readnone
  %11 = load volatile i64* %clock, align 8
  %call5 = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([21 x i8]* @.str1, i32 0, i32 0), i32 %call3, i64 %call4, i64 %11)
  store i64 0, i64* %oi, align 8
  ; Error here due to %8
  %OldFuncCounter7 = load i64* getelementptr inbounds ([16 x i64]* @EdgeProfCounters, i64 0, i64 %8)
  ;
  %NewFuncCounter8 = add i64 %OldFuncCounter7, 13
  store volatile i64 %NewFuncCounter8, i64* getelementptr inbounds ([16 x i64]* @EdgeProfCounters, i64 0, i64 0)
  br label %for.cond6

Upvotes: 4

Views: 2318

Answers (1)

Oak
Oak

Reputation: 26898

You are using %8 from within a constant expression, but it is not a constant. You need to fix your code to perform the getelementptr instruction outside of a constant expression:

%temp = getelementptr inbounds [16 x i64]* @EdgeProfCounters, i64 0, i64 %8
%OldFuncCounter7 = load i64* %temp

Upvotes: 4

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