[llvm] [LV] Also clamp MaxVF by trip count when maximizing vector bandwidth. (PR #149794)

[David Sherwood via llvm-commits]

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@@ -6,96 +6,41 @@ target triple = "aarch64-linux-gnu"
 define i64 @main_vector_loop_fixed_with_no_remaining_iterations(ptr %src, ptr noalias %dst, i32 %x) #0 {
 ; CHECK-LABEL: define i64 @main_vector_loop_fixed_with_no_remaining_iterations(
 ; CHECK-SAME: ptr [[SRC:%.*]], ptr noalias [[DST:%.*]], i32 [[X:%.*]]) #[[ATTR0:[0-9]+]] {
-; CHECK-NEXT:  [[ITER_CHECK:.*]]:
-; CHECK-NEXT:    [[TMP2:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP3:%.*]] = mul nuw i64 [[TMP2]], 2
-; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ule i64 16, [[TMP3]]
-; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label %[[VEC_EPILOG_SCALAR_PH:.*]], label %[[VECTOR_MAIN_LOOP_ITER_CHECK:.*]]
-; CHECK:       [[VECTOR_MAIN_LOOP_ITER_CHECK]]:
-; CHECK-NEXT:    br i1 true, label %[[VEC_EPILOG_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
 ; CHECK:       [[VECTOR_PH]]:
-; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <16 x i32> poison, i32 [[X]], i64 0
-; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <16 x i32> [[BROADCAST_SPLATINSERT]], <16 x i32> poison, <16 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP0:%.*]] = call <16 x i32> @llvm.abs.v16i32(<16 x i32> [[BROADCAST_SPLAT]], i1 false)
-; CHECK-NEXT:    [[TMP1:%.*]] = call <16 x i32> @llvm.abs.v16i32(<16 x i32> [[BROADCAST_SPLAT]], i1 false)
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <8 x i32> poison, i32 [[X]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <8 x i32> [[BROADCAST_SPLATINSERT]], <8 x i32> poison, <8 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP0:%.*]] = call <8 x i32> @llvm.abs.v8i32(<8 x i32> [[BROADCAST_SPLAT]], i1 false)
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david-arm wrote:

Does this change mean that it's no longer actually testing a main loop fixed-width VF with no remaining iterations? It interacts with https://github.com/llvm/llvm-project/pull/149789

https://github.com/llvm/llvm-project/pull/149794