[Mesa-dev] [PATCH 1/6] i965: Add negative_equals methods

[Alejandro Piñeiro]

Looks good in general, just a comment below.


On 22/03/18 01:58, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> This method is similar to the existing ::equals methods.  Instead of
> testing that two src_regs are equal to each other, it tests that one is
> the negation of the other.
>
> v2: Simplify various checks based on suggestions from Matt.  Use
> src_reg::type instead of fixed_hw_reg.type in a check.  Also suggested
> by Matt.
>
> v3: Rebase on 3 years.  Fix some problems with negative_equals with VF
> constants.  Add fs_reg::negative_equals.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/intel/compiler/brw_fs.cpp     |  7 ++++++
>  src/intel/compiler/brw_ir_fs.h    |  1 +
>  src/intel/compiler/brw_ir_vec4.h  |  1 +
>  src/intel/compiler/brw_reg.h      | 46 +++++++++++++++++++++++++++++++++++++++
>  src/intel/compiler/brw_shader.cpp |  6 +++++
>  src/intel/compiler/brw_shader.h   |  1 +
>  src/intel/compiler/brw_vec4.cpp   |  7 ++++++
>  7 files changed, 69 insertions(+)
>
> diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
> index 6eea532..3d454c3 100644
> --- a/src/intel/compiler/brw_fs.cpp
> +++ b/src/intel/compiler/brw_fs.cpp
> @@ -454,6 +454,13 @@ fs_reg::equals(const fs_reg &r) const
>  }
>  
>  bool
> +fs_reg::negative_equals(const fs_reg &r) const
> +{
> +   return (this->backend_reg::negative_equals(r) &&
> +           stride == r.stride);
> +}
> +
> +bool
>  fs_reg::is_contiguous() const
>  {
>     return stride == 1;
> diff --git a/src/intel/compiler/brw_ir_fs.h b/src/intel/compiler/brw_ir_fs.h
> index 54797ff..f06a33c 100644
> --- a/src/intel/compiler/brw_ir_fs.h
> +++ b/src/intel/compiler/brw_ir_fs.h
> @@ -41,6 +41,7 @@ public:
>     fs_reg(enum brw_reg_file file, int nr, enum brw_reg_type type);
>  
>     bool equals(const fs_reg &r) const;
> +   bool negative_equals(const fs_reg &r) const;
>     bool is_contiguous() const;
>  
>     /**
> diff --git a/src/intel/compiler/brw_ir_vec4.h b/src/intel/compiler/brw_ir_vec4.h
> index cbaff2f..95c5119 100644
> --- a/src/intel/compiler/brw_ir_vec4.h
> +++ b/src/intel/compiler/brw_ir_vec4.h
> @@ -43,6 +43,7 @@ public:
>     src_reg(struct ::brw_reg reg);
>  
>     bool equals(const src_reg &r) const;
> +   bool negative_equals(const src_reg &r) const;
>  
>     src_reg(class vec4_visitor *v, const struct glsl_type *type);
>     src_reg(class vec4_visitor *v, const struct glsl_type *type, int size);
> diff --git a/src/intel/compiler/brw_reg.h b/src/intel/compiler/brw_reg.h
> index 7ad144b..732bddf 100644
> --- a/src/intel/compiler/brw_reg.h
> +++ b/src/intel/compiler/brw_reg.h
> @@ -255,6 +255,52 @@ brw_regs_equal(const struct brw_reg *a, const struct brw_reg *b)
>     return a->bits == b->bits && (df ? a->u64 == b->u64 : a->ud == b->ud);
>  }
>  
> +static inline bool
> +brw_regs_negative_equal(const struct brw_reg *a, const struct brw_reg *b)
> +{
> +   if (a->file == IMM) {
> +      if (a->bits != b->bits)
> +         return false;
> +
> +      switch (a->type) {
> +      case BRW_REGISTER_TYPE_UQ:
> +      case BRW_REGISTER_TYPE_Q:
> +         return a->d64 == -b->d64;
> +      case BRW_REGISTER_TYPE_DF:
> +         return a->df == -b->df;
> +      case BRW_REGISTER_TYPE_UD:
> +      case BRW_REGISTER_TYPE_D:
> +         return a->d == -b->d;
> +      case BRW_REGISTER_TYPE_F:
> +         return a->f == -b->f;
> +      case BRW_REGISTER_TYPE_VF:
> +         /* It is tempting to treat 0 as a negation of 0 (and -0 as a negation
> +          * of -0).  There are occasions where 0 or -0 is used and the exact
> +          * bit pattern is desired.  At the very least, changing this to allow
> +          * 0 as a negation of 0 causes some fp64 tests to fail on IVB.
> +          */
> +         return a->ud == (b->ud ^ 0x80808080);
> +      case BRW_REGISTER_TYPE_UW:
> +      case BRW_REGISTER_TYPE_W:
> +      case BRW_REGISTER_TYPE_UV:
> +      case BRW_REGISTER_TYPE_V:
> +      case BRW_REGISTER_TYPE_HF:
> +      case BRW_REGISTER_TYPE_UB:
> +      case BRW_REGISTER_TYPE_B:
> +         /* FINISHME: Implement support for these types. */

Is this missing functionality on purpose or the patch is still a wip? If
it is the former, perhaps it would be good to explain why it is ok to
leave that functionality hole.

> +         return false;
> +      default:
> +         unreachable("not reached");
> +      }
> +   } else {
> +      struct brw_reg tmp = *a;
> +
> +      tmp.negate = !tmp.negate;
> +
> +      return brw_regs_equal(&tmp, b);
> +   }
> +}
> +
>  struct brw_indirect {
>     unsigned addr_subnr:4;
>     int addr_offset:10;
> diff --git a/src/intel/compiler/brw_shader.cpp b/src/intel/compiler/brw_shader.cpp
> index 054962b..9cdf9fc 100644
> --- a/src/intel/compiler/brw_shader.cpp
> +++ b/src/intel/compiler/brw_shader.cpp
> @@ -685,6 +685,12 @@ backend_reg::equals(const backend_reg &r) const
>  }
>  
>  bool
> +backend_reg::negative_equals(const backend_reg &r) const
> +{
> +   return brw_regs_negative_equal(this, &r) && offset == r.offset;
> +}
> +
> +bool
>  backend_reg::is_zero() const
>  {
>     if (file != IMM)
> diff --git a/src/intel/compiler/brw_shader.h b/src/intel/compiler/brw_shader.h
> index fd02feb..7d97ddb 100644
> --- a/src/intel/compiler/brw_shader.h
> +++ b/src/intel/compiler/brw_shader.h
> @@ -59,6 +59,7 @@ struct backend_reg : private brw_reg
>     }
>  
>     bool equals(const backend_reg &r) const;
> +   bool negative_equals(const backend_reg &r) const;
>  
>     bool is_zero() const;
>     bool is_one() const;
> diff --git a/src/intel/compiler/brw_vec4.cpp b/src/intel/compiler/brw_vec4.cpp
> index e483814..6680410 100644
> --- a/src/intel/compiler/brw_vec4.cpp
> +++ b/src/intel/compiler/brw_vec4.cpp
> @@ -376,6 +376,13 @@ src_reg::equals(const src_reg &r) const
>  }
>  
>  bool
> +src_reg::negative_equals(const src_reg &r) const
> +{
> +   return this->backend_reg::negative_equals(r) &&
> +          !reladdr && !r.reladdr;
> +}
> +
> +bool
>  vec4_visitor::opt_vector_float()
>  {
>     bool progress = false;