[PATCH] D65033: LowerTypeTests: Teach the pass to respect global alignments.

[Peter Collingbourne via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
pcc marked an inline comment as done.
Closed by commit rL366722: LowerTypeTests: Teach the pass to respect global alignments. (authored by pcc, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D65033?vs=210942&id=211159#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65033/new/

https://reviews.llvm.org/D65033

Files:
  llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
  llvm/trunk/test/Transforms/LowerTypeTests/align.ll


Index: llvm/trunk/test/Transforms/LowerTypeTests/align.ll
===================================================================
--- llvm/trunk/test/Transforms/LowerTypeTests/align.ll
+++ llvm/trunk/test/Transforms/LowerTypeTests/align.ll
@@ -0,0 +1,16 @@
+; RUN: opt -S -lowertypetests < %s | FileCheck %s
+
+target datalayout = "e-p:32:32"
+
+; CHECK: private constant { i32, [4 x i8], i32 } { i32 1, [4 x i8] zeroinitializer, i32 2 }, align 8
+ at a = constant i32 1, !type !0
+ at b = constant i32 2, align 8, !type !0
+
+!0 = !{i32 0, !"typeid1"}
+
+declare i1 @llvm.type.test(i8* %ptr, metadata %bitset) nounwind readnone
+
+define i1 @foo(i8* %p) {
+  %x = call i1 @llvm.type.test(i8* %p, metadata !"typeid1")
+  ret i1 %x
+}
Index: llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
+++ llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -759,43 +759,50 @@
   // Build a new global with the combined contents of the referenced globals.
   // This global is a struct whose even-indexed elements contain the original
   // contents of the referenced globals and whose odd-indexed elements contain
-  // any padding required to align the next element to the next power of 2.
+  // any padding required to align the next element to the next power of 2 plus
+  // any additional padding required to meet its alignment requirements.
   std::vector<Constant *> GlobalInits;
   const DataLayout &DL = M.getDataLayout();
+  DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout;
+  uint64_t MaxAlign = 0;
+  uint64_t CurOffset = 0;
+  uint64_t DesiredPadding = 0;
   for (GlobalTypeMember *G : Globals) {
-    GlobalVariable *GV = cast<GlobalVariable>(G->getGlobal());
+    auto *GV = cast<GlobalVariable>(G->getGlobal());
+    uint64_t Align = GV->getAlignment();
+    if (Align == 0)
+      Align = DL.getABITypeAlignment(GV->getValueType());
+    MaxAlign = std::max(MaxAlign, Align);
+    uint64_t GVOffset = alignTo(CurOffset + DesiredPadding, Align);
+    GlobalLayout[G] = GVOffset;
+    if (GVOffset != 0) {
+      uint64_t Padding = GVOffset - CurOffset;
+      GlobalInits.push_back(
+          ConstantAggregateZero::get(ArrayType::get(Int8Ty, Padding)));
+    }
+
     GlobalInits.push_back(GV->getInitializer());
     uint64_t InitSize = DL.getTypeAllocSize(GV->getValueType());
+    CurOffset = GVOffset + InitSize;
 
-    // Compute the amount of padding required.
-    uint64_t Padding = NextPowerOf2(InitSize - 1) - InitSize;
+    // Compute the amount of padding that we'd like for the next element.
+    DesiredPadding = NextPowerOf2(InitSize - 1) - InitSize;
 
     // Experiments of different caps with Chromium on both x64 and ARM64
     // have shown that the 32-byte cap generates the smallest binary on
     // both platforms while different caps yield similar performance.
     // (see https://lists.llvm.org/pipermail/llvm-dev/2018-July/124694.html)
-    if (Padding > 32)
-      Padding = alignTo(InitSize, 32) - InitSize;
-
-    GlobalInits.push_back(
-        ConstantAggregateZero::get(ArrayType::get(Int8Ty, Padding)));
+    if (DesiredPadding > 32)
+      DesiredPadding = alignTo(InitSize, 32) - InitSize;
   }
-  if (!GlobalInits.empty())
-    GlobalInits.pop_back();
+
   Constant *NewInit = ConstantStruct::getAnon(M.getContext(), GlobalInits);
   auto *CombinedGlobal =
       new GlobalVariable(M, NewInit->getType(), /*isConstant=*/true,
                          GlobalValue::PrivateLinkage, NewInit);
+  CombinedGlobal->setAlignment(MaxAlign);
 
   StructType *NewTy = cast<StructType>(NewInit->getType());
-  const StructLayout *CombinedGlobalLayout = DL.getStructLayout(NewTy);
-
-  // Compute the offsets of the original globals within the new global.
-  DenseMap<GlobalTypeMember *, uint64_t> GlobalLayout;
-  for (unsigned I = 0; I != Globals.size(); ++I)
-    // Multiply by 2 to account for padding elements.
-    GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I * 2);
-
   lowerTypeTestCalls(TypeIds, CombinedGlobal, GlobalLayout);
 
   // Build aliases pointing to offsets into the combined global for each


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