From c2c5e48ad587a99a92ce55265cce20fdb235af70 Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Wed, 18 Feb 2015 23:17:51 +0000
Subject: [PATCH] IR: Allow MDSubrange to have 'count: -1'

It turns out that `count: -1` is a special value indicating an empty
array, such as `Values` in:

    struct T {
      unsigned Count;
      int Values[];
    };

Handle it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229769 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AsmParser/LLParser.cpp                         |  2 +-
 .../Assembler/invalid-mdsubrange-count-negative.ll |  7 +++++--
 test/Assembler/mdsubrange-empty-array.ll           | 14 ++++++++++++++
 unittests/IR/MetadataTest.cpp                      |  8 ++++++++
 4 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 test/Assembler/mdsubrange-empty-array.ll

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 76365ea2233..0d748610742 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -3276,7 +3276,7 @@ bool LLParser::ParseGenericDebugNode(MDNode *&Result, bool IsDistinct) {
 ///   ::= !MDSubrange(count: 30, lowerBound: 2)
 bool LLParser::ParseMDSubrange(MDNode *&Result, bool IsDistinct) {
 #define VISIT_MD_FIELDS(OPTIONAL, REQUIRED)                                    \
-  REQUIRED(count, MDUnsignedField, (0, UINT64_MAX >> 1));                      \
+  REQUIRED(count, MDSignedField, (-1, -1, INT64_MAX));                         \
   OPTIONAL(lowerBound, MDSignedField, );
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
diff --git a/test/Assembler/invalid-mdsubrange-count-negative.ll b/test/Assembler/invalid-mdsubrange-count-negative.ll
index 99cc8876750..92c0b4e7ca4 100644
--- a/test/Assembler/invalid-mdsubrange-count-negative.ll
+++ b/test/Assembler/invalid-mdsubrange-count-negative.ll
@@ -1,4 +1,7 @@
 ; RUN: not llvm-as < %s -disable-output 2>&1 | FileCheck %s
 
-; CHECK: [[@LINE+1]]:25: error: expected unsigned integer
-!0 = !MDSubrange(count: -3)
+; CHECK-NOT: error
+!0 = !MDSubrange(count: -1)
+
+; CHECK: <stdin>:[[@LINE+1]]:25: error: value for 'count' too small, limit is -1
+!0 = !MDSubrange(count: -2)
diff --git a/test/Assembler/mdsubrange-empty-array.ll b/test/Assembler/mdsubrange-empty-array.ll
new file mode 100644
index 00000000000..fa05582a9a9
--- /dev/null
+++ b/test/Assembler/mdsubrange-empty-array.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+; RUN: verify-uselistorder %s
+
+; CHECK: !named = !{!0, !0, !1, !2}
+!named = !{!0, !1, !2, !3}
+
+; CHECK:      !0 = !MDSubrange(count: -1)
+; CHECK-NEXT: !1 = !MDSubrange(count: -1, lowerBound: 4)
+; CHECK-NEXT: !2 = !MDSubrange(count: -1, lowerBound: -5)
+!0 = !MDSubrange(count: -1)
+!1 = !MDSubrange(count: -1, lowerBound: 0)
+
+!2 = !MDSubrange(count: -1, lowerBound: 4)
+!3 = !MDSubrange(count: -1, lowerBound: -5)
diff --git a/unittests/IR/MetadataTest.cpp b/unittests/IR/MetadataTest.cpp
index fc2ed73d89c..b6ee46a5d7b 100644
--- a/unittests/IR/MetadataTest.cpp
+++ b/unittests/IR/MetadataTest.cpp
@@ -670,6 +670,14 @@ TEST_F(MDSubrangeTest, get) {
   EXPECT_EQ(N, MDNode::replaceWithUniqued(std::move(Temp)));
 }
 
+TEST_F(MDSubrangeTest, getEmptyArray) {
+  auto *N = MDSubrange::get(Context, -1, 0);
+  EXPECT_EQ(dwarf::DW_TAG_subrange_type, N->getTag());
+  EXPECT_EQ(-1, N->getCount());
+  EXPECT_EQ(0, N->getLo());
+  EXPECT_EQ(N, MDSubrange::get(Context, -1, 0));
+}
+
 typedef MetadataTest MDEnumeratorTest;
 
 TEST_F(MDEnumeratorTest, get) {
-- 
2.34.1