From 5ece35df8586d0cb8c104a9f44eaae771de025f5 Mon Sep 17 00:00:00 2001
From: Haopeng Liu <153236845+haopliu@users.noreply.github.com>
Date: Fri, 21 Jun 2024 12:09:00 -0700
Subject: Add the 'initializes' attribute langref and support (#84803)

We propose adding a new LLVM attribute,
`initializes((Lo1,Hi1),(Lo2,Hi2),...)`, which expresses the notion of
memory space (i.e., intervals, in bytes) that the argument pointing to
is initialized in the function.

Will commit the attribute inferring in the follow-up PRs.


https://discourse.llvm.org/t/rfc-llvm-new-initialized-parameter-attribute-for-improved-interprocedural-dse/77337
---
 llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 49 +++++++++++++++++++++++++++----
 1 file changed, 44 insertions(+), 5 deletions(-)

(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 6bcd0c1..6c6c5d5 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -30,6 +30,7 @@
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/Constant.h"
+#include "llvm/IR/ConstantRangeList.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfo.h"
@@ -838,10 +839,10 @@ private:
   }
 
   Expected<ConstantRange> readConstantRange(ArrayRef<uint64_t> Record,
-                                            unsigned &OpNum) {
-    if (Record.size() - OpNum < 3)
+                                            unsigned &OpNum,
+                                            unsigned BitWidth) {
+    if (Record.size() - OpNum < 2)
       return error("Too few records for range");
-    unsigned BitWidth = Record[OpNum++];
     if (BitWidth > 64) {
       unsigned LowerActiveWords = Record[OpNum];
       unsigned UpperActiveWords = Record[OpNum++] >> 32;
@@ -861,6 +862,14 @@ private:
     }
   }
 
+  Expected<ConstantRange>
+  readBitWidthAndConstantRange(ArrayRef<uint64_t> Record, unsigned &OpNum) {
+    if (Record.size() - OpNum < 1)
+      return error("Too few records for range");
+    unsigned BitWidth = Record[OpNum++];
+    return readConstantRange(Record, OpNum, BitWidth);
+  }
+
   /// 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.
@@ -2174,6 +2183,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::DeadOnUnwind;
   case bitc::ATTR_KIND_RANGE:
     return Attribute::Range;
+  case bitc::ATTR_KIND_INITIALIZES:
+    return Attribute::Initializes;
   }
 }
 
@@ -2352,12 +2363,39 @@ Error BitcodeReader::parseAttributeGroupBlock() {
           if (!Attribute::isConstantRangeAttrKind(Kind))
             return error("Not a ConstantRange attribute");
 
-          Expected<ConstantRange> MaybeCR = readConstantRange(Record, i);
+          Expected<ConstantRange> MaybeCR =
+              readBitWidthAndConstantRange(Record, i);
           if (!MaybeCR)
             return MaybeCR.takeError();
           i--;
 
           B.addConstantRangeAttr(Kind, MaybeCR.get());
+        } else if (Record[i] == 8) {
+          Attribute::AttrKind Kind;
+
+          i++;
+          if (Error Err = parseAttrKind(Record[i++], &Kind))
+            return Err;
+          if (!Attribute::isConstantRangeListAttrKind(Kind))
+            return error("Not a constant range list attribute");
+
+          SmallVector<ConstantRange, 2> Val;
+          if (i + 2 > e)
+            return error("Too few records for constant range list");
+          unsigned RangeSize = Record[i++];
+          unsigned BitWidth = Record[i++];
+          for (unsigned Idx = 0; Idx < RangeSize; ++Idx) {
+            Expected<ConstantRange> MaybeCR =
+                readConstantRange(Record, i, BitWidth);
+            if (!MaybeCR)
+              return MaybeCR.takeError();
+            Val.push_back(MaybeCR.get());
+          }
+          i--;
+
+          if (!ConstantRangeList::isOrderedRanges(Val))
+            return error("Invalid (unordered or overlapping) range list");
+          B.addConstantRangeListAttr(Kind, Val);
         } else {
           return error("Invalid attribute group entry");
         }
@@ -3372,7 +3410,8 @@ Error BitcodeReader::parseConstants() {
         (void)InRangeIndex;
       } else if (BitCode == bitc::CST_CODE_CE_GEP_WITH_INRANGE) {
         Flags = Record[OpNum++];
-        Expected<ConstantRange> MaybeInRange = readConstantRange(Record, OpNum);
+        Expected<ConstantRange> MaybeInRange =
+            readBitWidthAndConstantRange(Record, OpNum);
         if (!MaybeInRange)
           return MaybeInRange.takeError();
         InRange = MaybeInRange.get();
-- 
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