From 9bd6b02f5cc4cadef798403663297a789c4b6cf4 Mon Sep 17 00:00:00 2001
From: David Zarzycki <dave@znu.io>
Date: Mon, 4 May 2020 07:03:02 -0400
Subject: [PATCH] [SILOpt] Add ZeroInitializer to isValidStaticInitializerInst

---
 lib/IRGen/GenConstant.cpp               | 37 +++++++++++++++++++++
 lib/IRGen/GenConstant.h                 |  3 ++
 lib/SIL/IR/SILGlobalVariable.cpp        |  6 ++++
 test/SILOptimizer/zeroInitializer.swift | 44 +++++++++++++++++++++++++
 4 files changed, 90 insertions(+)
 create mode 100644 test/SILOptimizer/zeroInitializer.swift

diff --git a/lib/IRGen/GenConstant.cpp b/lib/IRGen/GenConstant.cpp
index c8bd8efb530e0..6855b0ccadf94 100644
--- a/lib/IRGen/GenConstant.cpp
+++ b/lib/IRGen/GenConstant.cpp
@@ -56,6 +56,41 @@ llvm::Constant *irgen::emitConstantInt(IRGenModule &IGM,
   return llvm::ConstantInt::get(IGM.getLLVMContext(), value);
 }
 
+llvm::Constant *irgen::emitConstantZero(IRGenModule &IGM, BuiltinInst *BI) {
+  assert(IGM.getSILModule().getBuiltinInfo(BI->getName()).ID ==
+         BuiltinValueKind::ZeroInitializer);
+
+  auto helper = [&](CanType astType) -> llvm::Constant * {
+    if (auto type = astType->getAs<BuiltinIntegerType>()) {
+      APInt zero(type->getWidth().getLeastWidth(), 0);
+      return llvm::ConstantInt::get(IGM.getLLVMContext(), zero);
+    }
+
+    if (auto type = astType->getAs<BuiltinFloatType>()) {
+      const llvm::fltSemantics *sema = nullptr;
+      switch (type->getFPKind()) {
+      case BuiltinFloatType::IEEE16: sema = &APFloat::IEEEhalf(); break;
+      case BuiltinFloatType::IEEE32: sema = &APFloat::IEEEsingle(); break;
+      case BuiltinFloatType::IEEE64: sema = &APFloat::IEEEdouble(); break;
+      case BuiltinFloatType::IEEE80: sema = &APFloat::x87DoubleExtended(); break;
+      case BuiltinFloatType::IEEE128: sema = &APFloat::IEEEquad(); break;
+      case BuiltinFloatType::PPC128: sema = &APFloat::PPCDoubleDouble(); break;
+      }
+      auto zero = APFloat::getZero(*sema);
+      return llvm::ConstantFP::get(IGM.getLLVMContext(), zero);
+    }
+
+    llvm_unreachable("SIL allowed an unknown type?");
+  };
+
+  if (auto vector = BI->getType().getAs<BuiltinVectorType>()) {
+    auto zero = helper(vector.getElementType());
+    return llvm::ConstantVector::getSplat(vector->getNumElements(), zero);
+  }
+
+  return helper(BI->getType().getASTType());
+}
+
 llvm::Constant *irgen::emitConstantFP(IRGenModule &IGM, FloatLiteralInst *FLI) {
   return llvm::ConstantFP::get(IGM.getLLVMContext(), FLI->getValue());
 }
@@ -94,6 +129,8 @@ static llvm::Constant *emitConstantValue(IRGenModule &IGM, SILValue operand) {
     return emitAddrOfConstantString(IGM, SLI);
   } else if (auto *BI = dyn_cast<BuiltinInst>(operand)) {
     switch (IGM.getSILModule().getBuiltinInfo(BI->getName()).ID) {
+      case BuiltinValueKind::ZeroInitializer:
+        return emitConstantZero(IGM, BI);
       case BuiltinValueKind::PtrToInt: {
         llvm::Constant *ptr = emitConstantValue(IGM, BI->getArguments()[0]);
         return llvm::ConstantExpr::getPtrToInt(ptr, IGM.IntPtrTy);
diff --git a/lib/IRGen/GenConstant.h b/lib/IRGen/GenConstant.h
index 3a5c23adb0911..faa67fcc8114f 100644
--- a/lib/IRGen/GenConstant.h
+++ b/lib/IRGen/GenConstant.h
@@ -27,6 +27,9 @@ namespace irgen {
 /// Construct a ConstantInt from an IntegerLiteralInst.
 llvm::Constant *emitConstantInt(IRGenModule &IGM, IntegerLiteralInst *ILI);
 
+/// Construct a zero from a zero intializer BuiltinInst.
+llvm::Constant *emitConstantZero(IRGenModule &IGM, BuiltinInst *Bi);
+
 /// Construct a ConstantFP from a FloatLiteralInst.
 llvm::Constant *emitConstantFP(IRGenModule &IGM, FloatLiteralInst *FLI);
 
diff --git a/lib/SIL/IR/SILGlobalVariable.cpp b/lib/SIL/IR/SILGlobalVariable.cpp
index 733ad528dcd52..a7473bbd287e6 100644
--- a/lib/SIL/IR/SILGlobalVariable.cpp
+++ b/lib/SIL/IR/SILGlobalVariable.cpp
@@ -109,6 +109,12 @@ bool SILGlobalVariable::isValidStaticInitializerInst(const SILInstruction *I,
     case SILInstructionKind::BuiltinInst: {
       auto *bi = cast<BuiltinInst>(I);
       switch (M.getBuiltinInfo(bi->getName()).ID) {
+        case BuiltinValueKind::ZeroInitializer: {
+          auto type = bi->getType().getASTType();
+          if (auto vector = dyn_cast<BuiltinVectorType>(type))
+            type = vector.getElementType();
+          return isa<BuiltinIntegerType>(type) || isa<BuiltinFloatType>(type);
+        }
         case BuiltinValueKind::PtrToInt:
           if (isa<LiteralInst>(bi->getArguments()[0]))
             return true;
diff --git a/test/SILOptimizer/zeroInitializer.swift b/test/SILOptimizer/zeroInitializer.swift
new file mode 100644
index 0000000000000..83b8f861c5f04
--- /dev/null
+++ b/test/SILOptimizer/zeroInitializer.swift
@@ -0,0 +1,44 @@
+// RUN: %target-swift-frontend -O -parse-stdlib -emit-ir -module-name ZeroInit -verify %s | %FileCheck %s
+
+import Swift
+
+@frozen
+public struct TestInt {
+  @usableFromInline
+  var _value : Builtin.Int32
+  @_transparent
+  public init() {
+    _value = Builtin.zeroInitializer()
+  }
+}
+
+@frozen
+public struct TestFloat {
+  @usableFromInline
+  var _value : Builtin.FPIEEE32
+  @_transparent
+  public init() {
+    _value = Builtin.zeroInitializer()
+  }
+}
+
+@frozen
+public struct TestVector {
+  @usableFromInline
+  var _value : Builtin.Vec4xFPIEEE32
+  @_transparent
+  public init() {
+    _value = Builtin.zeroInitializer()
+  }
+}
+
+public struct Foo {
+  public static var x : TestInt = TestInt()
+  public static var y : TestFloat = TestFloat()
+  public static var z : TestVector = TestVector()
+}
+
+// CHECK: @"$s8ZeroInit3FooV1xAA7TestIntVvpZ" ={{.*}} global %T8ZeroInit7TestIntV zeroinitializer
+// CHECK: @"$s8ZeroInit3FooV1yAA9TestFloatVvpZ" ={{.*}} global %T8ZeroInit9TestFloatV zeroinitializer
+// CHECK: @"$s8ZeroInit3FooV1zAA10TestVectorVvpZ" ={{.*}} global %T8ZeroInit10TestVectorV zeroinitializer
+// CHECK-NOT: swift_once