[AArch64][GlobalISel] Legalize large G_SEXT_INREG

These come from the legalization of other operations, but it makes sense to
split the operations into legal sizes before lowering them.

Author: davemgreen

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

@@ -623,6 +623,10 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
       .legalFor({s32, s64})
       .legalFor(PackedVectorAllTypeList)
       .maxScalar(0, s64)
+      .clampNumElements(0, v8s8, v16s8)
+      .clampNumElements(0, v4s16, v8s16)
+      .clampNumElements(0, v2s32, v4s32)
+      .clampMaxNumElements(0, s64, 2)
       .lower();
 
   // FP conversions

llvm/test/CodeGen/AArch64/aarch64-addv.ll

@@ -23,14 +23,14 @@ declare i64 @llvm.vector.reduce.add.v3i64(<3 x i64>)
 declare i64 @llvm.vector.reduce.add.v4i64(<4 x i64>)
 declare i128 @llvm.vector.reduce.add.v2i128(<2 x i128>)
 
-; GISEL:        warning: Instruction selection used fallback path for addv_v2i8
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v3i8
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v4i8
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v2i16
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v3i16
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v3i32
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v3i64
-; GISEL-NEXT:   warning: Instruction selection used fallback path for addv_v2i128
+; GISEL:       warning: Instruction selection used fallback path for addv_v2i8
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v3i8
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v4i8
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v2i16
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v3i16
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v3i32
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v3i64
+; GISEL-NEXT:  warning: Instruction selection used fallback path for addv_v2i128
 
 
 define i8 @add_B(ptr %arr)  {
@@ -101,16 +101,12 @@ define i32 @oversized_ADDV_256(ptr noalias nocapture readonly %arg1, ptr noalias
 ; GISEL-NEXT:    ushll v2.8h, v2.8b, #0
 ; GISEL-NEXT:    usubl v3.4s, v1.4h, v2.4h
 ; GISEL-NEXT:    usubl2 v1.4s, v1.8h, v2.8h
-; GISEL-NEXT:    cmgt v2.4s, v0.4s, v3.4s
+; GISEL-NEXT:    neg v2.4s, v3.4s
+; GISEL-NEXT:    neg v4.4s, v1.4s
+; GISEL-NEXT:    cmgt v5.4s, v0.4s, v3.4s
 ; GISEL-NEXT:    cmgt v0.4s, v0.4s, v1.4s
-; GISEL-NEXT:    neg v4.4s, v3.4s
-; GISEL-NEXT:    neg v5.4s, v1.4s
-; GISEL-NEXT:    shl v2.4s, v2.4s, #31
-; GISEL-NEXT:    shl v0.4s, v0.4s, #31
-; GISEL-NEXT:    sshr v2.4s, v2.4s, #31
-; GISEL-NEXT:    sshr v0.4s, v0.4s, #31
-; GISEL-NEXT:    bsl v2.16b, v4.16b, v3.16b
-; GISEL-NEXT:    bsl v0.16b, v5.16b, v1.16b
+; GISEL-NEXT:    bif v2.16b, v3.16b, v5.16b
+; GISEL-NEXT:    bsl v0.16b, v4.16b, v1.16b
 ; GISEL-NEXT:    add v0.4s, v2.4s, v0.4s
 ; GISEL-NEXT:    addv s0, v0.4s
 ; GISEL-NEXT:    fmov w0, s0