diff --git a/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll
@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --filter "LV: Found an estimated cost of [0-9]+ for VF [0-9]+ For instruction:\s*%v0 = load float, float\* %in0, align 4"
+; RUN: opt -loop-vectorize -vectorizer-maximize-bandwidth -S -mattr=+avx512bw --debug-only=loop-vectorize < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,AVX512
+; REQUIRES: asserts
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@A = global [1024 x float] zeroinitializer, align 128
+@B = global [1024 x i8] zeroinitializer, align 128
+
+define void @test() {
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+
+  %iv.0 = add nuw nsw i64 %iv, 0
+  %iv.1 = add nuw nsw i64 %iv, 1
+
+  %in0 = getelementptr inbounds [1024 x float], [1024 x float]* @A, i64 0, i64 %iv.0
+  %in1 = getelementptr inbounds [1024 x float], [1024 x float]* @A, i64 0, i64 %iv.1
+
+  %v0 = load float, float* %in0
+  %v1 = load float, float* %in1
+
+  %reduce.add.0 = fadd float %v0, %v1
+
+  %reduce.add.0.narrow = fptoui float %reduce.add.0 to i8
+
+  %out = getelementptr inbounds [1024 x i8], [1024 x i8]* @B, i64 0, i64 %iv.0
+  store i8 %reduce.add.0.narrow, i8* %out
+
+  %iv.next = add nuw nsw i64 %iv.0, 2
+  %cmp = icmp ult i64 %iv.next, 1024
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll.expected b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/Inputs/x86-loopvectorize-costmodel.ll.expected
@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --filter "LV: Found an estimated cost of [0-9]+ for VF [0-9]+ For instruction:\s*%v0 = load float, float\* %in0, align 4"
+; RUN: opt -loop-vectorize -vectorizer-maximize-bandwidth -S -mattr=+avx512bw --debug-only=loop-vectorize < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,AVX512
+; REQUIRES: asserts
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@A = global [1024 x float] zeroinitializer, align 128
+@B = global [1024 x i8] zeroinitializer, align 128
+
+define void @test() {
+; CHECK-LABEL: 'test'
+; CHECK:  LV: Found an estimated cost of 1 for VF 1 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 3 for VF 2 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 3 for VF 4 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 3 for VF 8 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 5 for VF 16 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 22 for VF 32 For instruction: %v0 = load float, float* %in0, align 4
+; CHECK:  LV: Found an estimated cost of 92 for VF 64 For instruction: %v0 = load float, float* %in0, align 4
+;
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+
+  %iv.0 = add nuw nsw i64 %iv, 0
+  %iv.1 = add nuw nsw i64 %iv, 1
+
+  %in0 = getelementptr inbounds [1024 x float], [1024 x float]* @A, i64 0, i64 %iv.0
+  %in1 = getelementptr inbounds [1024 x float], [1024 x float]* @A, i64 0, i64 %iv.1
+
+  %v0 = load float, float* %in0
+  %v1 = load float, float* %in1
+
+  %reduce.add.0 = fadd float %v0, %v1
+
+  %reduce.add.0.narrow = fptoui float %reduce.add.0 to i8
+
+  %out = getelementptr inbounds [1024 x i8], [1024 x i8]* @B, i64 0, i64 %iv.0
+  store i8 %reduce.add.0.narrow, i8* %out
+
+  %iv.next = add nuw nsw i64 %iv.0, 2
+  %cmp = icmp ult i64 %iv.next, 1024
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/loopvectorize-costmodel.test b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/loopvectorize-costmodel.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_analyze_test_checks/loopvectorize-costmodel.test
@@ -0,0 +1,13 @@
+# REQUIRES: x86-registered-target
+
+## Check that --filter works properly.
+# RUN: cp -f %S/Inputs/x86-loopvectorize-costmodel.ll %t.ll && %update_analyze_test_checks --filter "LV: Found an estimated cost of [0-9]+ for VF [0-9]+ For instruction:\s*%v0 = load float, float\* %in0, align 4" %t.ll
+# RUN: diff -u %t.ll %S/Inputs/x86-loopvectorize-costmodel.ll.expected
+
+## Check that running the script again does not change the result:
+# RUN: %update_analyze_test_checks --filter "LV: Found an estimated cost of [0-9]+ for VF [0-9]+ For instruction:\s*%v0 = load float, float\* %in0, align 4" %t.ll
+# RUN: diff -u %t.ll %S/Inputs/x86-loopvectorize-costmodel.ll.expected
+
+## Check that running the script again, without arguments, does not change the result:
+# RUN: %update_analyze_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/x86-loopvectorize-costmodel.ll.expected
diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -303,6 +303,11 @@
     r'\s*\n(?P<body>.*)$',
     flags=(re.X | re.S))
 
+LV_DEBUG_RE = re.compile(
+    r'^\s*\'(?P<func>[\w.$-]+?)\'[^\n]*'
+    r'\s*\n(?P<body>.*)$',
+    flags=(re.X | re.S))
+
 IR_FUNCTION_RE = re.compile(r'^\s*define\s+(?:internal\s+)?[^@]*@"?([\w.$-]+)"?\s*\(')
 TRIPLE_IR_RE = re.compile(r'^\s*target\s+triple\s*=\s*"([^"]+)"$')
 TRIPLE_ARG_RE = re.compile(r'-mtriple[= ]([^ ]+)')
diff --git a/llvm/utils/update_analyze_test_checks.py b/llvm/utils/update_analyze_test_checks.py
--- a/llvm/utils/update_analyze_test_checks.py
+++ b/llvm/utils/update_analyze_test_checks.py
@@ -110,10 +110,19 @@
 
       raw_tool_outputs = common.invoke_tool(ti.args.opt_binary, opt_args, ti.path)
 
-      # Split analysis outputs by "Printing analysis " declarations.
-      for raw_tool_output in re.split(r'Printing analysis ', raw_tool_outputs):
-        builder.process_run_line(common.ANALYZE_FUNCTION_RE, common.scrub_body,
-                                 raw_tool_output, prefixes, False)
+      if re.search(r'Printing analysis ', raw_tool_outputs) is not None:
+        # Split analysis outputs by "Printing analysis " declarations.
+        for raw_tool_output in re.split(r'Printing analysis ', raw_tool_outputs):
+          builder.process_run_line(common.ANALYZE_FUNCTION_RE, common.scrub_body,
+                                  raw_tool_output, prefixes, False)
+      elif re.search(r'LV: Checking a loop in ', raw_tool_outputs) is not None:
+        # Split analysis outputs by "Printing analysis " declarations.
+        for raw_tool_output in re.split(r'LV: Checking a loop in ', raw_tool_outputs):
+          builder.process_run_line(common.LV_DEBUG_RE, common.scrub_body,
+                                  raw_tool_output, prefixes, False)
+      else:
+        common.warn('Don\'t know how to deal with this output')
+        continue
 
     func_dict = builder.finish_and_get_func_dict()
     is_in_function = False