[llvm] [LV] Vectorize FMax w/o fast-math flags. (PR #146711)

[Florian Hahn via llvm-commits]

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@@ -317,10 +449,58 @@ define float @fmax_with_select_and_load_store(ptr %src, ptr noalias %dst, i64 %n
 ; CHECK-LABEL: define float @fmax_with_select_and_load_store(
 ; CHECK-SAME: ptr [[SRC:%.*]], ptr noalias [[DST:%.*]], i64 [[N:%.*]]) {
 ; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[N]], 4
+; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK:       [[VECTOR_PH]]:
+; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N]], 4
+; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[N]], [[N_MOD_VF]]
+; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
+; CHECK:       [[VECTOR_BODY]]:
+; CHECK-NEXT:    [[IV1:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <4 x i64> [ <i64 0, i64 1, i64 2, i64 3>, %[[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <4 x i64> [ splat (i64 -1), %[[VECTOR_PH]] ], [ [[TMP9:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI1:%.*]] = phi <4 x float> [ splat (float -1.000000e+07), %[[VECTOR_PH]] ], [ [[TMP8:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[GEP_SRC1:%.*]] = getelementptr inbounds nuw float, ptr [[SRC]], i64 [[IV1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds nuw float, ptr [[GEP_SRC1]], i32 0
+; CHECK-NEXT:    [[WIDE_LOAD:%.*]] = load <4 x float>, ptr [[TMP1]], align 4
+; CHECK-NEXT:    [[TMP2:%.*]] = fcmp ugt <4 x float> [[WIDE_LOAD]], [[VEC_PHI1]]
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fhahn wrote:

FindFirstIV returns the lowest value in the reduction vector, ensuring that we pick the first induction value in the vector, irrespective of the predicate used to select the values of the vectors. Perhaps the naming could be improved, as regular FindFirstIV is only generated for reductions involving decrementing inductions.

https://github.com/llvm/llvm-project/pull/146711