[llvm-commits] [Review Request][PATCH] Refactor BBVectorize: Initialize the MaxIter to

[Hal Finkel]

Ether,

This does not look right because v is changed as v *= 2 in each loop,
not incremented by one like an iteration count. You'd still need to
compare v and n separately.

Thanks again,
Hal

On Thu, 5 Apr 2012 22:36:28 +0800
Hongbin Zheng <etherzhhb at gmail.com> wrote:

> Hi Hal,
> 
> This is a rather trivial patch which initialize the "MaxIter" with
> UINT_MAX, so that later in the loop invoking MaxIter we can replace
> v <= Config.VectorBits && (!Config.MaxIter || n <= Config.MaxIter)
> 
> by
> 
> v <= std::min(Config.VectorBits,Config.MaxIter)
> 
> Any comment?
> 
> best regards
> ether
> 
> ---
>  lib/Transforms/Vectorize/BBVectorize.cpp |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/Transforms/Vectorize/BBVectorize.cpp
> b/lib/Transforms/Vectorize/BBVectorize.cpp
> index 7672d5c..5a714c8 100644
> --- a/lib/Transforms/Vectorize/BBVectorize.cpp
> +++ b/lib/Transforms/Vectorize/BBVectorize.cpp
> @@ -43,6 +43,7 @@
>  #include "llvm/Target/TargetData.h"
>  #include "llvm/Transforms/Vectorize.h"
>  #include <algorithm>
> +#include <climits>
>  #include <map>
>  using namespace llvm;
> 
> @@ -63,7 +64,7 @@ VectorBits("bb-vectorize-vector-bits",
> cl::init(128), cl::Hidden,
>    cl::desc("The size of the native vector registers"));
> 
>  static cl::opt<unsigned>
> -MaxIter("bb-vectorize-max-iter", cl::init(0), cl::Hidden,
> +MaxIter("bb-vectorize-max-iter", cl::init(UINT_MAX), cl::Hidden,
>    cl::desc("The maximum number of pairing iterations"));
> 
>  static cl::opt<unsigned>
> @@ -295,9 +296,8 @@ namespace {
>        // Iterate a sufficient number of times to merge types of size
> 1 bit, // then 2 bits, then 4, etc. up to half of the target vector
> width of the // target vector register.
> -      for (unsigned v = 2, n = 1;
> -           v <= Config.VectorBits && (!Config.MaxIter || n <=
> Config.MaxIter);
> -           v *= 2, ++n) {
> +      for (unsigned v = 2, n = 1, e =
> std::min(Config.VectorBits,Config.MaxIter);
> +           v <= e; v *= 2, ++n) {
>          DEBUG(dbgs() << "BBV: fusing loop #" << n <<
>                " for " << BB.getName() << " in " <<
>                BB.getParent()->getName() << "...\n");



-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory