DAG: Combine extract_vector_elt of concat_vectors

Fixes extra canonicalize regressions when legalizing
vector fminnum/fmaxnum.

Author: arsenm

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -17604,6 +17604,27 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
       Elt = (Idx < (int)NumElts) ? Idx : Idx - (int)NumElts;
       Index = DAG.getConstant(Elt, DL, Index.getValueType());
     }
+  } else if (VecOp.getOpcode() == ISD::CONCAT_VECTORS &&
+             !BCNumEltsChanged && VecVT.getVectorElementType() == ScalarVT) {
+    // extract_vector_elt (concat_vectors v2i16:a, v2i16:b), 0
+    //      -> extract_vector_elt a, 0
+    // extract_vector_elt (concat_vectors v2i16:a, v2i16:b), 1
+    //      -> extract_vector_elt a, 1
+    // extract_vector_elt (concat_vectors v2i16:a, v2i16:b), 2
+    //      -> extract_vector_elt b, 0
+    // extract_vector_elt (concat_vectors v2i16:a, v2i16:b), 3
+    //      -> extract_vector_elt b, 1
+    SDLoc SL(N);
+    EVT ConcatVT = VecOp.getOperand(0).getValueType();
+    unsigned ConcatNumElts = ConcatVT.getVectorNumElements();
+    SDValue NewIdx = DAG.getConstant(Elt % ConcatNumElts, SL,
+                                     Index.getValueType());
+
+    SDValue ConcatOp = VecOp.getOperand(Elt / ConcatNumElts);
+    SDValue Elt = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, SL,
+                              ConcatVT.getVectorElementType(),
+                              ConcatOp, NewIdx);
+    return DAG.getNode(ISD::BITCAST, SL, ScalarVT, Elt);
   }
 
   // Make sure we found a non-volatile load and the extractelement is

llvm/test/CodeGen/AMDGPU/reduction.ll

@@ -438,10 +438,8 @@ entry:
 ; GFX9-NEXT: v_pk_max_f16 [[CANON1:v[0-9]+]], v1, v1
 ; GFX9-NEXT: v_pk_max_f16 [[CANON0:v[0-9]+]], v0, v0
 ; GFX9-NEXT: v_pk_max_f16 [[MAX:v[0-9]+]], [[CANON0]], [[CANON1]]{{$}}
+; GFX9-NEXT: v_max_f16_sdwa v{{[0-9]+}}, [[MAX]], [[MAX]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:DWORD src1_sel:WORD_1
 
-; FIXME: Extra canonicalize leftover
-; GFX9-NEXT: v_max_f16_sdwa [[TMP:v[0-9]+]], [[MAX]], [[MAX]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
-; GFX9-NEXT: v_max_f16_e32 v0, [[MAX]], [[TMP]]
 
 ; VI-DAG: v_max_f16_sdwa [[CANON1:v[0-9]+]], v0, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
 ; VI-DAG: v_max_f16_sdwa [[CANON3:v[0-9]+]], v1, v1 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
@@ -466,11 +464,7 @@ entry:
 ; GFX9-NEXT: v_pk_max_f16 [[CANON1:v[0-9]+]], v1, v1
 ; GFX9-NEXT: v_pk_max_f16 [[CANON0:v[0-9]+]], v0, v0
 ; GFX9-NEXT: v_pk_min_f16 [[MIN:v[0-9]+]], [[CANON0]], [[CANON1]]{{$}}
-
-; FIXME: Extra canonicalize leftover
-; GFX9-NEXT: v_max_f16_sdwa [[TMP:v[0-9]+]], [[MIN]], [[MIN]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
-; GFX9-NEXT: v_min_f16_e32 v0, [[MIN]], [[TMP]]
-
+; GFX9-NEXT: v_min_f16_sdwa v{{[0-9]+}}, [[MIN]], [[MIN]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:DWORD src1_sel:WORD_1
 
 ; VI-DAG: v_max_f16_sdwa [[CANON1:v[0-9]+]], v0, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
 ; VI-DAG: v_max_f16_sdwa [[CANON3:v[0-9]+]], v1, v1 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
@@ -507,10 +501,7 @@ entry:
 ; GFX9-NEXT: v_pk_max_f16 [[CANON1:v[0-9]+]], v1, v1
 ; GFX9-NEXT: v_pk_max_f16 [[CANON0:v[0-9]+]], v0, v0
 ; GFX9-NEXT: v_pk_max_f16 [[MAX:v[0-9]+]], [[CANON0]], [[CANON1]]{{$}}
-
-; FIXME: Extra canonicalize leftover
-; GFX9-NEXT: v_max_f16_sdwa [[TMP:v[0-9]+]], [[MAX]], [[MAX]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
-; GFX9-NEXT: v_max_f16_e32 v0, [[MAX]], [[TMP]]
+; GFX9-NEXT: v_max_f16_sdwa v{{[0-9]+}}, [[MAX]], [[MAX]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:DWORD src1_sel:WORD_1
 
 ; VI-DAG: v_max_f16_sdwa [[CANON1:v[0-9]+]], v0, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
 ; VI-DAG: v_max_f16_sdwa [[CANON3:v[0-9]+]], v1, v1 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
@@ -549,11 +540,7 @@ entry:
 ; GFX9-NEXT: v_pk_max_f16 [[CANON1:v[0-9]+]], v1, v1
 ; GFX9-NEXT: v_pk_max_f16 [[CANON0:v[0-9]+]], v0, v0
 ; GFX9-NEXT: v_pk_min_f16 [[MIN:v[0-9]+]], [[CANON0]], [[CANON1]]{{$}}
-
-; FIXME: Extra canonicalize leftover
-; GFX9-NEXT: v_max_f16_sdwa [[TMP:v[0-9]+]], [[MIN]], [[MIN]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
-; GFX9-NEXT: v_min_f16_e32 v0, [[MIN]], [[TMP]]
-
+; GFX9-NEXT: v_min_f16_sdwa v{{[0-9]+}}, [[MIN]], [[MIN]] dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:DWORD src1_sel:WORD_1
 
 ; VI-DAG: v_max_f16_sdwa [[CANON1:v[0-9]+]], v0, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1
 ; VI-DAG: v_max_f16_sdwa [[CANON3:v[0-9]+]], v1, v1 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:WORD_1