[llvm] [LoopReduceMotion] Improve loop by extract reduction instruction (PR #179215)

[via llvm-commits]

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@@ -9,361 +9,325 @@ define dso_local i32 @test(ptr noundef %p1, i32 noundef %s_p1, ptr noundef %p2,
 ; CHECK-O3-LABEL: define dso_local i32 @test(
 ; CHECK-O3-SAME: ptr noundef readonly captures(none) [[P1:%.*]], i32 noundef [[S_P1:%.*]], ptr noundef readonly captures(none) [[P2:%.*]], i32 noundef [[S_P2:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
 ; CHECK-O3-NEXT:  [[ENTRY:.*:]]
-; CHECK-O3-NEXT:    [[IDX_EXT8:%.*]] = sext i32 [[S_P2]] to i64
-; CHECK-O3-NEXT:    [[IDX_EXT:%.*]] = sext i32 [[S_P1]] to i64
 ; CHECK-O3-NEXT:    [[TMP0:%.*]] = load <16 x i8>, ptr [[P1]], align 1, !tbaa [[CHAR_TBAA0:![0-9]+]]
 ; CHECK-O3-NEXT:    [[TMP1:%.*]] = zext <16 x i8> [[TMP0]] to <16 x i16>
 ; CHECK-O3-NEXT:    [[TMP2:%.*]] = load <16 x i8>, ptr [[P2]], align 1, !tbaa [[CHAR_TBAA0]]
 ; CHECK-O3-NEXT:    [[TMP3:%.*]] = zext <16 x i8> [[TMP2]] to <16 x i16>
 ; CHECK-O3-NEXT:    [[TMP4:%.*]] = sub nsw <16 x i16> [[TMP1]], [[TMP3]]
 ; CHECK-O3-NEXT:    [[TMP5:%.*]] = tail call <16 x i16> @llvm.abs.v16i16(<16 x i16> [[TMP4]], i1 false)
 ; CHECK-O3-NEXT:    [[TMP6:%.*]] = zext <16 x i16> [[TMP5]] to <16 x i32>
-; CHECK-O3-NEXT:    [[TMP7:%.*]] = tail call i32 @llvm.vector.reduce.add.v16i32(<16 x i32> [[TMP6]])
+; CHECK-O3-NEXT:    [[IDX_EXT:%.*]] = sext i32 [[S_P1]] to i64
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Anjian-Wen wrote:

Great suggestions，`preferInLoopReduction` is a good idea, I will try to enrich the costmodel with getExtendedReductionCost and getMulAccReductionCost and  more types of input‘s cost.

https://github.com/llvm/llvm-project/pull/179215