[LoopIdiom] Add test for simplifying SCEV during expansion with flags.

Author: fhahn

llvm/test/Transforms/LoopIdiom/expand-scev-expand-simplifications.ll

@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -p loop-idiom -S %s | FileCheck %s
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+
+define void @test_simplify_scev_during_expansion_flags(i64 %start) {
+; CHECK-LABEL: define void @test_simplify_scev_during_expansion_flags(
+; CHECK-SAME: i64 [[START:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[START_NEG:%.*]] = sub i64 0, [[START]]
+; CHECK-NEXT:    [[START_MUL:%.*]] = ashr exact i64 [[START_NEG]], 2
+; CHECK-NEXT:    [[TMP0:%.*]] = shl nsw i64 [[START_MUL]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 404, [[TMP0]]
+; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 4 null, i8 0, i64 [[TMP1]], i1 false)
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[START_MUL]], %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
+; CHECK-NEXT:    [[PTR_IV:%.*]] = phi ptr [ null, %[[ENTRY]] ], [ [[PTR_IV_NEXT:%.*]], %[[LOOP]] ]
+; CHECK-NEXT:    [[PTR_IV_NEXT]] = getelementptr i8, ptr [[PTR_IV]], i64 4
+; CHECK-NEXT:    [[IV_NEXT]] = add i64 [[IV]], 1
+; CHECK-NEXT:    [[EC:%.*]] = icmp eq i64 [[IV]], 100
+; CHECK-NEXT:    br i1 [[EC]], label %[[EXIT:.*]], label %[[LOOP]]
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %start.neg = sub i64 0, %start
+  %start.mul = ashr exact i64 %start.neg, 2
+  br label %loop
+
+loop:
+  %iv = phi i64 [ %start.mul, %entry ], [ %iv.next, %loop ]
+  %ptr.iv = phi ptr [ null, %entry ], [ %ptr.iv.next, %loop ]
+  store i32 0, ptr %ptr.iv, align 4
+  %ptr.iv.next = getelementptr i8, ptr %ptr.iv, i64 4
+  %iv.next = add i64 %iv, 1
+  %ec = icmp eq i64 %iv, 100
+  br i1 %ec, label %exit, label %loop
+
+exit:
+  ret void
+}