[llvm-dev] Help to understand LoadValueFromMemory

[Alberto Barbaro via llvm-dev]

Hi all,
I'm trying to print to screen the value read by the fread function. I'm at
the point where source refers to the GetElementPtrInst ( pointer to the
buffer where fread stored the data - %5 in my case ) and the fread() has
been already called.

I thought the correct approach to achieve what I need was:

ExecutionContext& SF = ECStack.back();
   GenericValue SRC = getOperandValue(source, SF);
   GenericValue* Ptr = (GenericValue*)GVTOP(SRC);
   GenericValue Result;

source->getPointerOperand()->getType()->dump(); //[40 x i8]*

LoadValueFromMemory(Result, Ptr, source->getPointerOperand()->getType());

and use Result.PointerVal ...

In the end I have the first 4 bytes within Result.PointrVal but I cannot
see the other bytes.. Unfortunately also Result.AggregateVal has size 0.

Could you help me to understand why please?

The core part of the .ll is the following:

define i32 @main() #0 {
  %1 = alloca i32, align 4
  %2 = alloca %struct._IO_FILE*, align 8
  %3 = alloca [40 x i8], align 16
  store i32 0, i32* %1, align 4
  %4 = call %struct._IO_FILE* @fopen(i8* getelementptr inbounds ([51 x i8],
[51 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([3 x i8], [3 x
i8]* @.str.1, i32 0, i32 0))
  store %struct._IO_FILE* %4, %struct._IO_FILE** %2, align 8
 * %5 = getelementptr inbounds [40 x i8], [40 x i8]* %3, i32 0, i32 0*
  %6 = load %struct._IO_FILE*, %struct._IO_FILE** %2, align 8
  *%7 = call i64 @fread(i8* %5, i64 30, i64 1, %struct._IO_FILE* %6)*
  %8 = load %struct._IO_FILE*, %struct._IO_FILE** %2, align 8
  %9 = call i32 @fclose(%struct._IO_FILE* %8)
  %10 = getelementptr inbounds [40 x i8], [40 x i8]* %3, i64 0, i64 0
  %11 = load i8, i8* %10, align 16
  %12 = sext i8 %11 to i32
  %13 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([9 x i8],
[9 x i8]* @.str.2, i32 0, i32 0), i32 %12)
  %14 = getelementptr inbounds [40 x i8], [40 x i8]* %3, i64 0, i64 0
  %15 = load i8, i8* %14, align 16
  %16 = sext i8 %15 to i32
  ret i32 %16
}

Thanks
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