From e0d49066c1acfa4ae0f0e8ea49b0f0b6bb3f1a25 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403@hotmail.com>
Date: Fri, 8 Mar 2024 16:20:04 +0100
Subject: [IR] Add new Range attribute using new ConstantRange Attribute type
 (#83171)

implementation as discussed in
https://discourse.llvm.org/t/rfc-metadata-attachments-for-function-arguments/76420
---
 llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 41 +++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

(limited to 'llvm/lib/Bitcode/Reader/BitcodeReader.cpp')

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 832907a..9c63116 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -815,6 +815,30 @@ private:
     return getFnValueByID(ValNo, Ty, TyID, ConstExprInsertBB);
   }
 
+  Expected<ConstantRange> readConstantRange(ArrayRef<uint64_t> Record,
+                                            unsigned &OpNum) {
+    if (Record.size() - OpNum < 3)
+      return error("Too few records for range");
+    unsigned BitWidth = Record[OpNum++];
+    if (BitWidth > 64) {
+      unsigned LowerActiveWords = Record[OpNum];
+      unsigned UpperActiveWords = Record[OpNum++] >> 32;
+      if (Record.size() - OpNum < LowerActiveWords + UpperActiveWords)
+        return error("Too few records for range");
+      APInt Lower =
+          readWideAPInt(ArrayRef(&Record[OpNum], LowerActiveWords), BitWidth);
+      OpNum += LowerActiveWords;
+      APInt Upper =
+          readWideAPInt(ArrayRef(&Record[OpNum], UpperActiveWords), BitWidth);
+      OpNum += UpperActiveWords;
+      return ConstantRange(Lower, Upper);
+    } else {
+      int64_t Start = BitcodeReader::decodeSignRotatedValue(Record[OpNum++]);
+      int64_t End = BitcodeReader::decodeSignRotatedValue(Record[OpNum++]);
+      return ConstantRange(APInt(BitWidth, Start), APInt(BitWidth, End));
+    }
+  }
+
   /// Upgrades old-style typeless byval/sret/inalloca attributes by adding the
   /// corresponding argument's pointee type. Also upgrades intrinsics that now
   /// require an elementtype attribute.
@@ -2103,6 +2127,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::CoroDestroyOnlyWhenComplete;
   case bitc::ATTR_KIND_DEAD_ON_UNWIND:
     return Attribute::DeadOnUnwind;
+  case bitc::ATTR_KIND_RANGE:
+    return Attribute::Range;
   }
 }
 
@@ -2272,6 +2298,21 @@ Error BitcodeReader::parseAttributeGroupBlock() {
             return error("Not a type attribute");
 
           B.addTypeAttr(Kind, HasType ? getTypeByID(Record[++i]) : nullptr);
+        } else if (Record[i] == 7) {
+          Attribute::AttrKind Kind;
+
+          i++;
+          if (Error Err = parseAttrKind(Record[i++], &Kind))
+            return Err;
+          if (!Attribute::isConstantRangeAttrKind(Kind))
+            return error("Not a ConstantRange attribute");
+
+          Expected<ConstantRange> MaybeCR = readConstantRange(Record, i);
+          if (!MaybeCR)
+            return MaybeCR.takeError();
+          i--;
+
+          B.addConstantRangeAttr(Kind, MaybeCR.get());
         } else {
           return error("Invalid attribute group entry");
         }
-- 
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