[LLVMdev] Your commit 149912 "Remove some dead code and tidy things up"...

[Duncan Sands]

Hi Chris, this was a very tempting commit to make, unfortunately it broke
pattern matching of vectors of booleans.  The problem is that a
ConstantDataVector is only formed if the element type is one of i8, i16, etc.
So vectors of funky types, or not so funky types like i1, are no longer
matched.  I noticed this while working on PR11948.  The good thing is that
the testcase there no longer crashes the compiler because earlier patterns
now fail to match :)  The bad thing is that a -instsimplify testcase like the
following no longer passes:
   define <2 x i1> @vectorselect1(<2 x i1> %cond) {
   ; CHECK: @vectorselect1
     %invert = xor <2 x i1> %cond, <i1 1, i1 1>
     %s = select <2 x i1> %invert, <2 x i32> <i32 0, i32 0>, <2 x i32> <i32 1, 
i32 1>
     %c = icmp ne <2 x i32> %s, <i32 0, i32 0>
     ret <2 x i1> %c
   ; CHECK: ret <2 x i1> %cond
   }

Ciao, Duncan.

> Index: PatternMatch.h
> ===================================================================
> --- PatternMatch.h      (revision 149911)
> +++ PatternMatch.h      (revision 149912)
> @@ -98,13 +98,6 @@
>        Res = &CI->getValue();
>        return true;
>      }
> -    // FIXME: Remove this.
> -    if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
> -      if (ConstantInt *CI =
> -          dyn_cast_or_null<ConstantInt>(CV->getSplatValue())) {
> -        Res = &CI->getValue();
> -        return true;
> -      }
>      if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(V))
>        if (ConstantInt *CI =
>            dyn_cast_or_null<ConstantInt>(CV->getSplatValue())) {
...