[PhaseOrdering] Add test for vector promotion regression (NFC)

Sample test where cfd594f causes
optimization regressions.

Author: nikic

llvm/test/Transforms/PhaseOrdering/swap-promotion.ll

@@ -0,0 +1,58 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -O1 < %s | FileCheck %s
+; RUN: opt -S -O2 < %s | FileCheck %s
+; RUN: opt -S -O3 < %s | FileCheck %s
+
+define void @swap(ptr %p1, ptr %p2) {
+; CHECK-LABEL: @swap(
+; CHECK-NEXT:    [[TMP1:%.*]] = load i64, ptr [[P1:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = load i64, ptr [[P2:%.*]], align 1
+; CHECK-NEXT:    store i64 [[TMP2]], ptr [[P1]], align 1
+; CHECK-NEXT:    store i64 [[TMP1]], ptr [[P2]], align 1
+; CHECK-NEXT:    ret void
+;
+  %tmp = alloca [2 x i32]
+  call void @llvm.memcpy.p0.p0.i64(ptr %tmp, ptr %p1, i64 8, i1 false)
+  call void @llvm.memcpy.p0.p0.i64(ptr %p1, ptr %p2, i64 8, i1 false)
+  call void @llvm.memcpy.p0.p0.i64(ptr %p2, ptr %tmp, i64 8, i1 false)
+  ret void
+}
+
+define i32 @test(i32 %n) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[P1_SROA_5_0:%.*]] = phi i32 [ 1, [[TMP0:%.*]] ], [ [[V2_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[P1_SROA_0_0:%.*]] = phi i32 [ 0, [[TMP0]] ], [ [[V1_INC:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[V1_INC]] = add i32 [[P1_SROA_0_0]], 1
+; CHECK-NEXT:    [[V2_NEXT]] = shl i32 [[P1_SROA_5_0]], 1
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i32 [[V1_INC]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[C]], label [[EXIT:%.*]], label [[LOOP]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i32 [[V2_NEXT]]
+;
+  %p1 = alloca [2 x i32]
+  %p2 = alloca [2 x i32]
+  %p1.2 = getelementptr i32, ptr %p1, i64 1
+  %p2.2 = getelementptr i32, ptr %p2, i64 1
+  store i32 0, ptr %p1
+  store i32 1, ptr %p1.2
+  br label %loop
+
+loop:
+  %v1 = load i32, ptr %p1
+  %v1.inc = add i32 %v1, 1
+  store i32 %v1.inc, ptr %p1
+  %v2 = load i32, ptr %p1.2
+  %v2.next = shl i32 %v2, 1
+  store i32 %v2.next, ptr %p1.2
+  %c = icmp eq i32 %v1.inc, %n
+  br i1 %c, label %exit, label %loop
+
+exit:
+  call void @swap(ptr %p1, ptr %p2)
+  %res = load i32, ptr %p2.2
+  ret i32 %res
+}
+
+declare void @llvm.memcpy.p0.p0.i64(ptr, ptr, i64, i1)