[PhaseOrdering] Add test for missed vectorization with vector::at calls.

This test illustrates missed vectorization of loops with multiple
std::vector::at calls, like

    int sum(std::vector<int> *A, std::vector<int> *B, int N) {
      int cost = 0;
      for (int i = 0; i < N; ++i)
        cost += A->at(i) + B->at(i);
      return cost;
    }

https://clang.godbolt.org/z/KbYoaPhvq

(cherry-picked from 39cc0b8c68b8d316954ecfac0d1f8498ea42866c)

Author: fhahn

llvm/test/Transforms/PhaseOrdering/AArch64/peel-multiple-unreachable-exits-for-vectorization.ll

@@ -0,0 +1,196 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -O2 -mtriple=arm64-apple-ios -S %s | FileCheck %s
+
+%vec = type { i64*, i64* }
+
+; Test to ensure a loop with multiple loads guarded by runtime-checks (like
+; from multiple calls to C++'s std::vector::at) can be vectorized after
+; hoisting the runtime checks out of the loop.
+
+define i64 @sum_2_at_with_int_conversion(%vec* %A, %vec* %B, i64 %N) {
+; CHECK-LABEL: @sum_2_at_with_int_conversion(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[GEP_START_I:%.*]] = getelementptr [[VEC:%.*]], %vec* [[A:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[START_I:%.*]] = load i64*, i64** [[GEP_START_I]], align 8
+; CHECK-NEXT:    [[GEP_END_I:%.*]] = getelementptr [[VEC]], %vec* [[A]], i64 0, i32 1
+; CHECK-NEXT:    [[END_I:%.*]] = load i64*, i64** [[GEP_END_I]], align 8
+; CHECK-NEXT:    [[START_INT_I:%.*]] = ptrtoint i64* [[START_I]] to i64
+; CHECK-NEXT:    [[END_INT_I:%.*]] = ptrtoint i64* [[END_I]] to i64
+; CHECK-NEXT:    [[SUB_I:%.*]] = sub i64 [[END_INT_I]], [[START_INT_I]]
+; CHECK-NEXT:    [[GEP_START_I1:%.*]] = getelementptr [[VEC]], %vec* [[B:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[GEP_END_I3:%.*]] = getelementptr [[VEC]], %vec* [[B]], i64 0, i32 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[AT_WITH_INT_CONVERSION_EXIT12:%.*]] ]
+; CHECK-NEXT:    [[SUM:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[SUM_NEXT:%.*]], [[AT_WITH_INT_CONVERSION_EXIT12]] ]
+; CHECK-NEXT:    [[INRANGE_I:%.*]] = icmp ult i64 [[SUB_I]], [[IV]]
+; CHECK-NEXT:    br i1 [[INRANGE_I]], label [[ERROR_I:%.*]], label [[AT_WITH_INT_CONVERSION_EXIT:%.*]]
+; CHECK:       error.i:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+; CHECK:       at_with_int_conversion.exit:
+; CHECK-NEXT:    [[START_I2:%.*]] = load i64*, i64** [[GEP_START_I1]], align 8
+; CHECK-NEXT:    [[END_I4:%.*]] = load i64*, i64** [[GEP_END_I3]], align 8
+; CHECK-NEXT:    [[START_INT_I5:%.*]] = ptrtoint i64* [[START_I2]] to i64
+; CHECK-NEXT:    [[END_INT_I6:%.*]] = ptrtoint i64* [[END_I4]] to i64
+; CHECK-NEXT:    [[SUB_I7:%.*]] = sub i64 [[END_INT_I6]], [[START_INT_I5]]
+; CHECK-NEXT:    [[INRANGE_I8:%.*]] = icmp ult i64 [[SUB_I7]], [[IV]]
+; CHECK-NEXT:    br i1 [[INRANGE_I8]], label [[ERROR_I11:%.*]], label [[AT_WITH_INT_CONVERSION_EXIT12]]
+; CHECK:       error.i11:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+; CHECK:       at_with_int_conversion.exit12:
+; CHECK-NEXT:    [[GEP_IDX_I:%.*]] = getelementptr i64, i64* [[START_I]], i64 [[IV]]
+; CHECK-NEXT:    [[LV_I:%.*]] = load i64, i64* [[GEP_IDX_I]], align 4
+; CHECK-NEXT:    [[GEP_IDX_I9:%.*]] = getelementptr i64, i64* [[START_I2]], i64 [[IV]]
+; CHECK-NEXT:    [[LV_I10:%.*]] = load i64, i64* [[GEP_IDX_I9]], align 4
+; CHECK-NEXT:    [[ADD:%.*]] = add i64 [[LV_I]], [[SUM]]
+; CHECK-NEXT:    [[SUM_NEXT]] = add i64 [[ADD]], [[LV_I10]]
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[C:%.*]] = icmp slt i64 [[IV]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[C]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i64 [[SUM_NEXT]]
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %sum = phi i64 [ 0, %entry ], [ %sum.next, %loop ]
+  %a = call i64 @at_with_int_conversion(%vec* %A, i64 %iv)
+  %b = call i64 @at_with_int_conversion(%vec* %B, i64 %iv)
+  %add = add i64 %a, %b
+  %sum.next = add i64 %sum, %add
+  %iv.next = add nuw nsw i64 %iv, 1
+  %c = icmp slt i64 %iv, %N
+  br i1 %c, label %loop, label %exit
+
+exit:
+  ret i64 %sum.next
+}
+
+define i64 @sum_3_at_with_int_conversion(%vec* %A, %vec* %B, %vec* %C, i64 %N) {
+; CHECK-LABEL: @sum_3_at_with_int_conversion(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[GEP_START_I:%.*]] = getelementptr [[VEC:%.*]], %vec* [[A:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[START_I:%.*]] = load i64*, i64** [[GEP_START_I]], align 8
+; CHECK-NEXT:    [[GEP_END_I:%.*]] = getelementptr [[VEC]], %vec* [[A]], i64 0, i32 1
+; CHECK-NEXT:    [[END_I:%.*]] = load i64*, i64** [[GEP_END_I]], align 8
+; CHECK-NEXT:    [[START_INT_I:%.*]] = ptrtoint i64* [[START_I]] to i64
+; CHECK-NEXT:    [[END_INT_I:%.*]] = ptrtoint i64* [[END_I]] to i64
+; CHECK-NEXT:    [[SUB_I:%.*]] = sub i64 [[END_INT_I]], [[START_INT_I]]
+; CHECK-NEXT:    [[GEP_START_I1:%.*]] = getelementptr [[VEC]], %vec* [[B:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[GEP_END_I3:%.*]] = getelementptr [[VEC]], %vec* [[B]], i64 0, i32 1
+; CHECK-NEXT:    [[GEP_START_I13:%.*]] = getelementptr [[VEC]], %vec* [[C:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[GEP_END_I15:%.*]] = getelementptr [[VEC]], %vec* [[C]], i64 0, i32 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[AT_WITH_INT_CONVERSION_EXIT24:%.*]] ]
+; CHECK-NEXT:    [[SUM:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[SUM_NEXT:%.*]], [[AT_WITH_INT_CONVERSION_EXIT24]] ]
+; CHECK-NEXT:    [[INRANGE_I:%.*]] = icmp ult i64 [[SUB_I]], [[IV]]
+; CHECK-NEXT:    br i1 [[INRANGE_I]], label [[ERROR_I:%.*]], label [[AT_WITH_INT_CONVERSION_EXIT:%.*]]
+; CHECK:       error.i:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+; CHECK:       at_with_int_conversion.exit:
+; CHECK-NEXT:    [[GEP_IDX_I:%.*]] = getelementptr i64, i64* [[START_I]], i64 [[IV]]
+; CHECK-NEXT:    [[LV_I:%.*]] = load i64, i64* [[GEP_IDX_I]], align 4
+; CHECK-NEXT:    [[START_I2:%.*]] = load i64*, i64** [[GEP_START_I1]], align 8
+; CHECK-NEXT:    [[END_I4:%.*]] = load i64*, i64** [[GEP_END_I3]], align 8
+; CHECK-NEXT:    [[START_INT_I5:%.*]] = ptrtoint i64* [[START_I2]] to i64
+; CHECK-NEXT:    [[END_INT_I6:%.*]] = ptrtoint i64* [[END_I4]] to i64
+; CHECK-NEXT:    [[SUB_I7:%.*]] = sub i64 [[END_INT_I6]], [[START_INT_I5]]
+; CHECK-NEXT:    [[INRANGE_I8:%.*]] = icmp ult i64 [[SUB_I7]], [[IV]]
+; CHECK-NEXT:    br i1 [[INRANGE_I8]], label [[ERROR_I11:%.*]], label [[AT_WITH_INT_CONVERSION_EXIT12:%.*]]
+; CHECK:       error.i11:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+; CHECK:       at_with_int_conversion.exit12:
+; CHECK-NEXT:    [[START_I14:%.*]] = load i64*, i64** [[GEP_START_I13]], align 8
+; CHECK-NEXT:    [[END_I16:%.*]] = load i64*, i64** [[GEP_END_I15]], align 8
+; CHECK-NEXT:    [[START_INT_I17:%.*]] = ptrtoint i64* [[START_I14]] to i64
+; CHECK-NEXT:    [[END_INT_I18:%.*]] = ptrtoint i64* [[END_I16]] to i64
+; CHECK-NEXT:    [[SUB_I19:%.*]] = sub i64 [[END_INT_I18]], [[START_INT_I17]]
+; CHECK-NEXT:    [[INRANGE_I20:%.*]] = icmp ult i64 [[SUB_I19]], [[IV]]
+; CHECK-NEXT:    br i1 [[INRANGE_I20]], label [[ERROR_I23:%.*]], label [[AT_WITH_INT_CONVERSION_EXIT24]]
+; CHECK:       error.i23:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+; CHECK:       at_with_int_conversion.exit24:
+; CHECK-NEXT:    [[GEP_IDX_I9:%.*]] = getelementptr i64, i64* [[START_I2]], i64 [[IV]]
+; CHECK-NEXT:    [[LV_I10:%.*]] = load i64, i64* [[GEP_IDX_I9]], align 4
+; CHECK-NEXT:    [[GEP_IDX_I21:%.*]] = getelementptr i64, i64* [[START_I14]], i64 [[IV]]
+; CHECK-NEXT:    [[LV_I22:%.*]] = load i64, i64* [[GEP_IDX_I21]], align 4
+; CHECK-NEXT:    [[ADD_1:%.*]] = add i64 [[LV_I]], [[SUM]]
+; CHECK-NEXT:    [[ADD_2:%.*]] = add i64 [[ADD_1]], [[LV_I10]]
+; CHECK-NEXT:    [[SUM_NEXT]] = add i64 [[ADD_2]], [[LV_I22]]
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp slt i64 [[IV]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i64 [[SUM_NEXT]]
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %sum = phi i64 [ 0, %entry ], [ %sum.next, %loop ]
+  %a = call i64 @at_with_int_conversion(%vec* %A, i64 %iv)
+  %b = call i64 @at_with_int_conversion(%vec* %B, i64 %iv)
+  %c = call i64 @at_with_int_conversion(%vec* %C, i64 %iv)
+  %add.1 = add i64 %a, %b
+  %add.2 = add i64 %add.1, %c
+  %sum.next = add i64 %sum, %add.2
+  %iv.next = add nuw nsw i64 %iv, 1
+  %cond = icmp slt i64 %iv, %N
+  br i1 %cond, label %loop, label %exit
+
+exit:
+  ret i64 %sum.next
+}
+
+
+define i64 @at_with_int_conversion(%vec* %ptr, i64 %idx) {
+; CHECK-LABEL: @at_with_int_conversion(
+; CHECK-NEXT:    [[GEP_START:%.*]] = getelementptr [[VEC:%.*]], %vec* [[PTR:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[START:%.*]] = load i64*, i64** [[GEP_START]], align 8
+; CHECK-NEXT:    [[GEP_END:%.*]] = getelementptr [[VEC]], %vec* [[PTR]], i64 0, i32 1
+; CHECK-NEXT:    [[END:%.*]] = load i64*, i64** [[GEP_END]], align 8
+; CHECK-NEXT:    [[START_INT:%.*]] = ptrtoint i64* [[START]] to i64
+; CHECK-NEXT:    [[END_INT:%.*]] = ptrtoint i64* [[END]] to i64
+; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[END_INT]], [[START_INT]]
+; CHECK-NEXT:    [[INRANGE:%.*]] = icmp ult i64 [[SUB]], [[IDX:%.*]]
+; CHECK-NEXT:    br i1 [[INRANGE]], label [[ERROR:%.*]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[GEP_IDX:%.*]] = getelementptr i64, i64* [[START]], i64 [[IDX]]
+; CHECK-NEXT:    [[LV:%.*]] = load i64, i64* [[GEP_IDX]], align 4
+; CHECK-NEXT:    ret i64 [[LV]]
+; CHECK:       error:
+; CHECK-NEXT:    tail call void @error()
+; CHECK-NEXT:    unreachable
+;
+  %gep.start = getelementptr %vec, %vec* %ptr, i64 0, i32 0
+  %start = load i64*, i64** %gep.start
+  %gep.end = getelementptr %vec, %vec* %ptr, i64 0, i32 1
+  %end = load i64*, i64** %gep.end
+  %start.int = ptrtoint i64* %start to i64
+  %end.int = ptrtoint i64* %end to i64
+  %sub = sub i64 %end.int, %start.int
+  %inrange = icmp ugt i64 %idx, %sub
+  br i1 %inrange, label %error, label %exit
+
+exit:
+  %gep.idx = getelementptr i64, i64* %start, i64 %idx
+  %lv = load i64, i64* %gep.idx
+  ret i64 %lv
+
+error:
+  call void @error()
+  unreachable
+}
+
+declare void @error()
+
+