Introduce experimental generic intrinsics for horizontal vector reductions.

- This change allows targets to opt-in to using them instead of the log2
  shufflevector algorithm.
- The SLP and Loop vectorizers have the common code to do shuffle reductions
  factored out into LoopUtils, and now have a unified interface for generating
  reductions regardless of the preference of the target. LoopUtils now uses TTI
  to determine what kind of reductions the target wants to handle.
- For CodeGen, basic legalization support is added.

Differential Revision: https://reviews.llvm.org/D30086



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302514 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 332 insertions, 0 deletions

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index dad99e3352d..dc6350c5520 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -11687,6 +11687,338 @@ Examples:
 
       %r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields float:r2 = (a * b) + c
 
+
+Experimental Vector Reduction Intrinsics
+----------------------------------------
+
+Horizontal reductions of vectors can be expressed using the following
+intrinsics. Each one takes a vector operand as an input and applies its
+respective operation across all elements of the vector, returning a single
+scalar result of the same element type.
+
+
+'``llvm.experimental.vector.reduce.add.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.add.i32.v4i32(<4 x i32> %a)
+      declare i64 @llvm.experimental.vector.reduce.add.i64.v2i64(<2 x i64> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.add.*``' intrinsics do an integer ``ADD``
+reduction of a vector, returning the result as a scalar. The return type matches
+the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.fadd.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare float @llvm.experimental.vector.reduce.fadd.f32.v4f32(float %acc, <4 x float> %a)
+      declare double @llvm.experimental.vector.reduce.fadd.f64.v2f64(double %acc, <2 x double> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.fadd.*``' intrinsics do a floating point
+``ADD`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+If the intrinsic call has fast-math flags, then the reduction will not preserve
+the associativity of an equivalent scalarized counterpart. If it does not have
+fast-math flags, then the reduction will be *ordered*, implying that the
+operation respects the associativity of a scalarized reduction.
+
+
+Arguments:
+""""""""""
+The first argument to this intrinsic is a scalar accumulator value, which is
+only used when there are no fast-math flags attached. This argument may be undef
+when fast-math flags are used.
+
+The second argument must be a vector of floating point values.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+      %fast = call fast float @llvm.experimental.vector.reduce.fadd.f32.v4f32(float undef, <4 x float> %input) ; fast reduction
+      %ord = call float @llvm.experimental.vector.reduce.fadd.f32.v4f32(float %acc, <4 x float> %input) ; ordered reduction
+
+
+'``llvm.experimental.vector.reduce.mul.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.mul.i32.v4i32(<4 x i32> %a)
+      declare i64 @llvm.experimental.vector.reduce.mul.i64.v2i64(<2 x i64> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.mul.*``' intrinsics do an integer ``MUL``
+reduction of a vector, returning the result as a scalar. The return type matches
+the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.fmul.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare float @llvm.experimental.vector.reduce.fmul.f32.v4f32(float %acc, <4 x float> %a)
+      declare double @llvm.experimental.vector.reduce.fmul.f64.v2f64(double %acc, <2 x double> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.fmul.*``' intrinsics do a floating point
+``MUL`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+If the intrinsic call has fast-math flags, then the reduction will not preserve
+the associativity of an equivalent scalarized counterpart. If it does not have
+fast-math flags, then the reduction will be *ordered*, implying that the
+operation respects the associativity of a scalarized reduction.
+
+
+Arguments:
+""""""""""
+The first argument to this intrinsic is a scalar accumulator value, which is
+only used when there are no fast-math flags attached. This argument may be undef
+when fast-math flags are used.
+
+The second argument must be a vector of floating point values.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+      %fast = call fast float @llvm.experimental.vector.reduce.fmul.f32.v4f32(float undef, <4 x float> %input) ; fast reduction
+      %ord = call float @llvm.experimental.vector.reduce.fmul.f32.v4f32(float %acc, <4 x float> %input) ; ordered reduction
+
+'``llvm.experimental.vector.reduce.and.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.and.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.and.*``' intrinsics do a bitwise ``AND``
+reduction of a vector, returning the result as a scalar. The return type matches
+the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.or.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.or.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.or.*``' intrinsics do a bitwise ``OR`` reduction
+of a vector, returning the result as a scalar. The return type matches the
+element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.xor.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.xor.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.xor.*``' intrinsics do a bitwise ``XOR``
+reduction of a vector, returning the result as a scalar. The return type matches
+the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.smax.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.smax.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.smax.*``' intrinsics do a signed integer
+``MAX`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.smin.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.smin.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.smin.*``' intrinsics do a signed integer
+``MIN`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.umax.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.umax.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.umax.*``' intrinsics do an unsigned
+integer ``MAX`` reduction of a vector, returning the result as a scalar. The
+return type matches the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.umin.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i32 @llvm.experimental.vector.reduce.umin.i32.v4i32(<4 x i32> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.umin.*``' intrinsics do an unsigned
+integer ``MIN`` reduction of a vector, returning the result as a scalar. The
+return type matches the element-type of the vector input.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of integer values.
+
+'``llvm.experimental.vector.reduce.fmax.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare float @llvm.experimental.vector.reduce.fmax.f32.v4f32(<4 x float> %a)
+      declare double @llvm.experimental.vector.reduce.fmax.f64.v2f64(<2 x double> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.fmax.*``' intrinsics do a floating point
+``MAX`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+If the intrinsic call has the ``nnan`` fast-math flag then the operation can
+assume that NaNs are not present in the input vector.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of floating point values.
+
+'``llvm.experimental.vector.reduce.fmin.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare float @llvm.experimental.vector.reduce.fmin.f32.v4f32(<4 x float> %a)
+      declare double @llvm.experimental.vector.reduce.fmin.f64.v2f64(<2 x double> %a)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.vector.reduce.fmin.*``' intrinsics do a floating point
+``MIN`` reduction of a vector, returning the result as a scalar. The return type
+matches the element-type of the vector input.
+
+If the intrinsic call has the ``nnan`` fast-math flag then the operation can
+assume that NaNs are not present in the input vector.
+
+Arguments:
+""""""""""
+The argument to this intrinsic must be a vector of floating point values.
+
 Half Precision Floating Point Intrinsics
 ----------------------------------------