[SPIRV] Support -fembed-bitcode=marker for non-shader modules

-fembed-bitcode=marker gets lowered as a [0 x i8] zeroinitialized global
variable. This is interpreted as a runtime-array and is not supported in
non-shaders.

To work around this, we replace the [0 x i8] by a zeroinitialized
single-element array.

Author: jmmartinez

llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp

@@ -236,6 +236,8 @@ class SPIRVEmitIntrinsics
 
   Instruction *buildLogicalAccessChainFromGEP(GetElementPtrInst &GEP);
 
+  bool promoteEmbddedBitcodeMarker(Module &M) const;
+
 public:
   static char ID;
   SPIRVEmitIntrinsics(SPIRVTargetMachine *TM = nullptr)
@@ -3007,9 +3009,43 @@ void SPIRVEmitIntrinsics::parseFunDeclarations(Module &M) {
   }
 }
 
+bool SPIRVEmitIntrinsics::promoteEmbddedBitcodeMarker(Module &M) const {
+  const SPIRVSubtarget *STI = TM->getSubtargetImpl();
+  if (STI->isShader())
+    return false;
+
+  GlobalVariable *EmbeddedBitcode = M.getNamedGlobal("llvm.embedded.module");
+  if (!EmbeddedBitcode)
+    return false;
+
+  ArrayType *AT = cast<ArrayType>(EmbeddedBitcode->getValueType());
+  if (AT->getNumElements() != 0)
+    return false;
+
+  // When compiling with -fembed-bitcode=marker, LLVM generates a [0 x i8]
+  // zeroinitialized global variable containing the bitcode. This results in an
+  // assert outside of shaders. As a workaround, we replace this global with a
+  // zeroinitialized [1 x i8].
+  ArrayType *AT1 = ArrayType::get(AT->getElementType(), 1);
+  Constant *ZeroInit = Constant::getNullValue(AT1);
+  GlobalVariable *NewEmbeddedBitcode = new GlobalVariable(
+      AT1, EmbeddedBitcode->isConstant(), EmbeddedBitcode->getLinkage(),
+      ZeroInit, "", EmbeddedBitcode->getThreadLocalMode(),
+      EmbeddedBitcode->getAddressSpace(),
+      EmbeddedBitcode->isExternallyInitialized());
+  NewEmbeddedBitcode->setSection(NewEmbeddedBitcode->getSection());
+  NewEmbeddedBitcode->takeName(EmbeddedBitcode);
+
+  M.insertGlobalVariable(NewEmbeddedBitcode);
+  EmbeddedBitcode->replaceAllUsesWith(NewEmbeddedBitcode);
+  EmbeddedBitcode->eraseFromParent();
+  return true;
+}
+
 bool SPIRVEmitIntrinsics::runOnModule(Module &M) {
   bool Changed = false;
 
+  Changed |= promoteEmbddedBitcodeMarker(M);
   parseFunDeclarations(M);
   insertConstantsForFPFastMathDefault(M);
 

llvm/test/CodeGen/SPIRV/fembed-bitcode-marker.ll

@@ -1,11 +1,21 @@
-; XFAIL: *
 ; RUN: llc -verify-machineinstrs -mtriple=spirv-unknown-unknown %s -o - | FileCheck %s
 ; RUN: %if spirv-tools %{ llc -mtriple=spirv-unknown-unknown %s -o - -filetype=obj | spirv-val %}
 
 @llvm.embedded.module = private constant [0 x i8] zeroinitializer, section ".llvmbc", align 1
 @llvm.cmdline = private constant [5 x i8] c"-cc1\00", section ".llvmcmd", align 1
 @llvm.compiler.used = appending global [2 x ptr] [ptr @llvm.embedded.module, ptr @llvm.cmdline], section "llvm.metadata"
 
+; CHECK-DAG: OpName [[FOO:%[0-9]+]] "foo"
+; CHECK-DAG: OpName [[MODULE:%[0-9]+]] "llvm.embedded.module"
+; CHECK-DAG: [[INT8:%[0-9]+]] = OpTypeInt 8 0
+; CHECK-DAG: [[INT32:%[0-9]+]] = OpTypeInt 32 0
+; CHECK-DAG: [[CONST_1_32:%[0-9]+]] = OpConstant [[INT32]] 1
+; CHECK-DAG: [[ARRAY_INT8x1:%[0-9]+]] = OpTypeArray [[INT8]] [[CONST_1_32]]
+; CHECK-DAG: [[POINTER:%[0-9]+]] = OpTypePointer Function [[ARRAY_INT8x1]]
+; CHECK-DAG: [[EMBEDDED_MODULE_INIT:%[0-9]+]] = OpConstantNull [[ARRAY_INT8x1]]
+; CHECK: [[FOO]] = OpFunction {{.*}} None {{.*}}
+; CHECK-DAG: {{%[0-9]+}} = OpVariable [[POINTER]] Function [[EMBEDDED_MODULE_INIT]]
+
 define spir_kernel void @foo() {
 entry:
   ret void