[llvm] [SPIR-V] Introduce support for 'spirv.Decorations' metadata node in SPIR-V Backend (PR #91736)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-spir-v

Author: Vyacheslav Levytskyy (VyacheslavLevytskyy)

<details>
<summary>Changes</summary>

This PR is to introduce support for 'spirv.Decorations' metadata node in SPIR-V Backend.
See also https://github.com/KhronosGroup/SPIRV-LLVM-Translator/blob/main/docs/SPIRVRepresentationInLLVM.rst that describes `spirv.Decorations` as an important part of SPIRV-friendly LLVM IR.

---
Full diff: https://github.com/llvm/llvm-project/pull/91736.diff


4 Files Affected:

- (modified) llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp (+7) 
- (modified) llvm/lib/Target/SPIRV/SPIRVUtils.cpp (+28) 
- (modified) llvm/lib/Target/SPIRV/SPIRVUtils.h (+4) 
- (added) llvm/test/CodeGen/SPIRV/spirv-decoration.ll (+19) 


``````````diff
diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
index cebe230d3e8ce..0a4e44e2dac70 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
@@ -691,6 +691,13 @@ Register SPIRVGlobalRegistry::buildGlobalVariable(
     buildOpDecorate(Reg, MIRBuilder, SPIRV::Decoration::BuiltIn,
                     {static_cast<uint32_t>(BuiltInId)});
 
+  // If it's a global variable with "spirv.Decorations" metadata node
+  // recognize it as a SPIR-V friendly LLVM IR and parse "spirv.Decorations"
+  // arguments.
+  MDNode *GVarMD = nullptr;
+  if (GVar && (GVarMD = GVar->getMetadata("spirv.Decorations")) != nullptr)
+    buildOpSpirvDecorations(Reg, MIRBuilder, GVarMD);
+
   return Reg;
 }
 
diff --git a/llvm/lib/Target/SPIRV/SPIRVUtils.cpp b/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
index 871b95a28068e..3f8613d2707b8 100644
--- a/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVUtils.cpp
@@ -133,6 +133,34 @@ void buildOpDecorate(Register Reg, MachineInstr &I, const SPIRVInstrInfo &TII,
   finishBuildOpDecorate(MIB, DecArgs, StrImm);
 }
 
+void buildOpSpirvDecorations(Register Reg, MachineIRBuilder &MIRBuilder,
+                             MDNode *GVarMD) {
+  for (unsigned I = 0, E = GVarMD->getNumOperands(); I != E; ++I) {
+    auto *OpMD = dyn_cast<MDNode>(GVarMD->getOperand(I));
+    if (!OpMD)
+      report_fatal_error("Invalid decoration");
+    if (OpMD->getNumOperands() == 0)
+      report_fatal_error("Expect operand(s) of the decoration");
+    ConstantInt *DecorationId =
+        mdconst::dyn_extract<ConstantInt>(OpMD->getOperand(0));
+    if (!DecorationId)
+      report_fatal_error("Expect SPIR-V <Decoration> operand to be the first "
+                         "element of the decoration");
+    auto MIB = MIRBuilder.buildInstr(SPIRV::OpDecorate)
+                   .addUse(Reg)
+                   .addImm(static_cast<uint32_t>(DecorationId->getZExtValue()));
+    for (unsigned OpI = 1, OpE = OpMD->getNumOperands(); OpI != OpE; ++OpI) {
+      if (ConstantInt *OpV =
+              mdconst::dyn_extract<ConstantInt>(OpMD->getOperand(OpI)))
+        MIB.addImm(static_cast<uint32_t>(OpV->getZExtValue()));
+      else if (MDString *OpV = dyn_cast<MDString>(OpMD->getOperand(OpI)))
+        addStringImm(OpV->getString(), MIB);
+      else
+        report_fatal_error("Unexpected operand of the decoration");
+    }
+  }
+}
+
 // TODO: maybe the following two functions should be handled in the subtarget
 // to allow for different OpenCL vs Vulkan handling.
 unsigned storageClassToAddressSpace(SPIRV::StorageClass::StorageClass SC) {
diff --git a/llvm/lib/Target/SPIRV/SPIRVUtils.h b/llvm/lib/Target/SPIRV/SPIRVUtils.h
index 6a91b6e576f9c..fbdc9bf75dbe1 100644
--- a/llvm/lib/Target/SPIRV/SPIRVUtils.h
+++ b/llvm/lib/Target/SPIRV/SPIRVUtils.h
@@ -59,6 +59,10 @@ void buildOpDecorate(Register Reg, MachineInstr &I, const SPIRVInstrInfo &TII,
                      const std::vector<uint32_t> &DecArgs,
                      StringRef StrImm = "");
 
+// Add an OpDecorate instruction by "spirv.Decorations" metadata node
+void buildOpSpirvDecorations(Register Reg, MachineIRBuilder &MIRBuilder,
+                             MDNode *GVarMD);
+
 // Convert a SPIR-V storage class to the corresponding LLVM IR address space.
 unsigned storageClassToAddressSpace(SPIRV::StorageClass::StorageClass SC);
 
diff --git a/llvm/test/CodeGen/SPIRV/spirv-decoration.ll b/llvm/test/CodeGen/SPIRV/spirv-decoration.ll
new file mode 100644
index 0000000000000..618646de93183
--- /dev/null
+++ b/llvm/test/CodeGen/SPIRV/spirv-decoration.ll
@@ -0,0 +1,19 @@
+; RUN: llc -O0 -mtriple=spirv64-unknown-unknown %s -o - | FileCheck %s
+; RUN: %if spirv-tools %{ llc -O0 -mtriple=spirv64-unknown-unknown %s -o - -filetype=obj | spirv-val %}
+
+; CHECK: OpName %[[#GV:]] "v"
+; CHECK-DAG: OpDecorate %[[#GV]] LinkageAttributes "v" Export
+; CHECK-DAG: OpDecorate %[[#GV]] Constant
+
+ at v = addrspace(1) global i32 0, !spirv.Decorations !0
+
+define spir_kernel void @foo() {
+entry:
+  %pv = load ptr addrspace(1), ptr addrspace(1) @v
+  store i32 3, ptr addrspace(1) %pv
+  ret void
+}
+
+!0 = !{!1, !2}
+!1 = !{i32 22}
+!2 = !{i32 41, !"v", i32 0}

``````````

</details>


https://github.com/llvm/llvm-project/pull/91736