[llvm-dev] Little explanation of this behaviour

[Lorenzo Laneve via llvm-dev]

I tried to emit IR for a function that returns the sum between an signed char and a double in C++, just to see how Clang handles type implicit casting.
Can you explain me why Clang converted the char type into a 32-bit integer type before casting it to a floating point? Can a sitofp i8 %3 to double be done or is it wrong?


define i32 @_Z5sumad(i8 signext %x, double %y) #0 {
  %1 = alloca i8, align 1
  %2 = alloca double, align 8
  store i8 %x, i8* %1, align 1
  store double %y, double* %2, align 8
  %3 = load i8, i8* %1, align 1
  %4 = sext i8 %3 to i32
  %5 = sitofp i32 %4 to double
  %6 = load double, double* %2, align 8
  %7 = fadd double %5, %6
  %8 = fptosi double %7 to i32
  ret i32 %8
}
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