[llvm] 61ec4cd - [ADT] Mix the bit width into APInt's hash_value

[David Blaikie via llvm-commits]

Ping on this discussion - I'm curious about the answer to Eli's question
too.

On Tue, Apr 14, 2020 at 12:31 PM Eli Friedman via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Why does it matter if they collide?  You can't stick two APInts with
> different widths into a hashtable anyway: the operator== asserts.
>
> -Eli
>
> -----Original Message-----
> From: llvm-commits <llvm-commits-bounces at lists.llvm.org> On Behalf Of
> Benjamin Kramer via llvm-commits
> Sent: Tuesday, April 14, 2020 9:19 AM
> To: llvm-commits at lists.llvm.org
> Subject: [EXT] [llvm] 61ec4cd - [ADT] Mix the bit width into APInt's
> hash_value
>
>
> Author: Benjamin Kramer
> Date: 2020-04-14T18:16:15+02:00
> New Revision: 61ec4cdf6be9f05c65f9cc2e8a1d05320305e9fb
>
> URL:
> https://github.com/llvm/llvm-project/commit/61ec4cdf6be9f05c65f9cc2e8a1d05320305e9fb
> DIFF:
> https://github.com/llvm/llvm-project/commit/61ec4cdf6be9f05c65f9cc2e8a1d05320305e9fb.diff
>
> LOG: [ADT] Mix the bit width into APInt's hash_value
>
> Otherwise all zero values from i1 to i64 collide.
>
> Added:
>
>
> Modified:
>     llvm/lib/Support/APInt.cpp
>
> Removed:
>
>
>
>
> ################################################################################
> diff  --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
> index faef9a31a0ed..4a591efb141a 100644
> --- a/llvm/lib/Support/APInt.cpp
> +++ b/llvm/lib/Support/APInt.cpp
> @@ -548,9 +548,11 @@ unsigned APInt::getBitsNeeded(StringRef str, uint8_t
> radix) {
>
>  hash_code llvm::hash_value(const APInt &Arg) {
>    if (Arg.isSingleWord())
> -    return hash_combine(Arg.U.VAL);
> +    return hash_combine(Arg.BitWidth, Arg.U.VAL);
>
> -  return hash_combine_range(Arg.U.pVal, Arg.U.pVal + Arg.getNumWords());
> +  return hash_combine(
> +      Arg.BitWidth,
> +      hash_combine_range(Arg.U.pVal, Arg.U.pVal + Arg.getNumWords()));
>  }
>
>  bool APInt::isSplat(unsigned SplatSizeInBits) const {
>
>
>
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