[IndVars] Add test for #126012 (NFC)

Author: nikic

llvm/test/Transforms/IndVarSimplify/pr126012.ll

@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=indvars < %s | FileCheck %s
+
+; FIXME: This is a miscompile.
+define i32 @test() {
+; CHECK-LABEL: define i32 @test() {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    br label %[[FOR_PREHEADER:.*]]
+; CHECK:       [[FOR_PREHEADER]]:
+; CHECK-NEXT:    [[INDVAR1:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[PHI:%.*]], %[[FOR_INC:.*]] ]
+; CHECK-NEXT:    [[INDVAR3:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[INC:%.*]], %[[FOR_INC]] ]
+; CHECK-NEXT:    [[COND1:%.*]] = icmp eq i32 [[INDVAR3]], 0
+; CHECK-NEXT:    br i1 [[COND1]], label %[[FOR_INC]], label %[[FOR_END:.*]]
+; CHECK:       [[FOR_END]]:
+; CHECK-NEXT:    [[EXT:%.*]] = zext i1 true to i32
+; CHECK-NEXT:    br label %[[FOR_INC]]
+; CHECK:       [[FOR_INC]]:
+; CHECK-NEXT:    [[PHI]] = phi i32 [ [[EXT]], %[[FOR_END]] ], [ 0, %[[FOR_PREHEADER]] ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[INDVAR3]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INDVAR3]], 2
+; CHECK-NEXT:    br i1 [[EXITCOND]], label %[[FOR_EXIT:.*]], label %[[FOR_PREHEADER]]
+; CHECK:       [[FOR_EXIT]]:
+; CHECK-NEXT:    [[INDVAR1_LCSSA:%.*]] = phi i32 [ [[INDVAR1]], %[[FOR_INC]] ]
+; CHECK-NEXT:    ret i32 [[INDVAR1_LCSSA]]
+;
+entry:
+  br label %for.preheader
+
+for.preheader:
+  %indvar1 = phi i32 [ 0, %entry ], [ %phi, %for.inc ]
+  %indvar2 = phi i32 [ 1, %entry ], [ %indvar3, %for.inc ]
+  %indvar3 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  %cond1 = icmp eq i32 %indvar3, 0
+  br i1 %cond1, label %for.inc, label %for.end
+
+for.end:
+  %cmp = icmp sgt i32 %indvar2, 0
+  %ext = zext i1 %cmp to i32
+  br label %for.inc
+
+for.inc:
+  %phi = phi i32 [ %ext, %for.end ], [ 0, %for.preheader ]
+  %inc = add i32 %indvar3, 1
+  %exitcond = icmp eq i32 %indvar3, 2
+  br i1 %exitcond, label %for.exit, label %for.preheader
+
+for.exit:
+  ret i32 %indvar1
+}