[LangRef][VP] Change masked-off lanes from undef to poison

These were all changed in 32b1b06 (as
discussed in D133967) but some intrinsics introduced since have
re-introduced `undef` as the masked-off value.

Reviewed By: reames, eopXD

Differential Revision: https://reviews.llvm.org/D135244

llvm/docs/LangRef.rst

@@ -19390,7 +19390,8 @@ Semantics:
 
 The '``llvm.vp.sqrt``' intrinsic performs floating-point square root (:ref:`sqrt <int_sqrt>`) of
 the first vector operand on each enabled lane.  The result on disabled lanes is
-undefined. The operation is performed in the default floating-point environment.
+a :ref:`poison value <poisonvalues>`. The operation is performed in the default
+floating-point environment.
 
 Examples:
 """""""""
@@ -19401,7 +19402,7 @@ Examples:
       ;; For all lanes below %evl, %r is lane-wise equivalent to %also.r
 
       %t = call <4 x float> @llvm.sqrt.v4f32(<4 x float> %a)
-      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> undef
+      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> poison
 
 
 .. _int_vp_fma:
@@ -21508,8 +21509,8 @@ Semantics:
 """"""""""
 
 The '``llvm.vp.ceil``' intrinsic performs floating-point ceiling
-(:ref:`ceil <int_ceil>`) of the first vector operand on each enabled lane.  The
-result on disabled lanes is undefined.
+(:ref:`ceil <int_ceil>`) of the first vector operand on each enabled lane. The
+result on disabled lanes is a :ref:`poison value <poisonvalues>`.
 
 Examples:
 """""""""
@@ -21520,7 +21521,7 @@ Examples:
       ;; For all lanes below %evl, %r is lane-wise equivalent to %also.r
 
       %t = call <4 x float> @llvm.ceil.v4f32(<4 x float> %a)
-      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> undef
+      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> poison
 
 .. _int_vp_floor:
 
@@ -21555,8 +21556,8 @@ Semantics:
 """"""""""
 
 The '``llvm.vp.floor``' intrinsic performs floating-point floor
-(:ref:`floor <int_floor>`) of the first vector operand on each enabled lane.  The
-result on disabled lanes is undefined.
+(:ref:`floor <int_floor>`) of the first vector operand on each enabled lane.
+The result on disabled lanes is a :ref:`poison value <poisonvalues>`.
 
 Examples:
 """""""""
@@ -21567,7 +21568,7 @@ Examples:
       ;; For all lanes below %evl, %r is lane-wise equivalent to %also.r
 
       %t = call <4 x float> @llvm.floor.v4f32(<4 x float> %a)
-      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> undef
+      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> poison
 
 .. _int_vp_round:
 
@@ -21602,8 +21603,8 @@ Semantics:
 """"""""""
 
 The '``llvm.vp.round``' intrinsic performs floating-point round
-(:ref:`round <int_round>`) of the first vector operand on each enabled lane.  The
-result on disabled lanes is undefined.
+(:ref:`round <int_round>`) of the first vector operand on each enabled lane.
+The result on disabled lanes is a :ref:`poison value <poisonvalues>`.
 
 Examples:
 """""""""
@@ -21614,7 +21615,7 @@ Examples:
       ;; For all lanes below %evl, %r is lane-wise equivalent to %also.r
 
       %t = call <4 x float> @llvm.round.v4f32(<4 x float> %a)
-      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> undef
+      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> poison
 
 .. _int_vp_roundeven:
 
@@ -21649,8 +21650,8 @@ Semantics:
 """"""""""
 
 The '``llvm.vp.roundeven``' intrinsic performs floating-point roundeven
-(:ref:`roundeven <int_roundeven>`) of the first vector operand on each enabled lane.  The
-result on disabled lanes is undefined.
+(:ref:`roundeven <int_roundeven>`) of the first vector operand on each enabled
+lane. The result on disabled lanes is a :ref:`poison value <poisonvalues>`.
 
 Examples:
 """""""""
@@ -21661,7 +21662,7 @@ Examples:
       ;; For all lanes below %evl, %r is lane-wise equivalent to %also.r
 
       %t = call <4 x float> @llvm.roundeven.v4f32(<4 x float> %a)
-      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> undef
+      %also.r = select <4 x i1> %mask, <4 x float> %t, <4 x float> poison
 
 .. _int_mload_mstore: