[SPIR-V] Stop generating StorageImageReadWithoutFormat and StorageImageWriteWithoutFormat for the Unknown image format in the OpenCL environment (llvm#128497)

This PR resolves the issue of the SPIR-V specification, requiring
Shader-coupled capabilities to read/write images in the OpenCL SPIR-V
environment, from the perspective of the LLVM SPIR-V backend. See
KhronosGroup/SPIRV-Headers#487 for details and
discussion.

Current implementation correctly reproduces requirements of the SPIR-V
specification, however, since the requirements are problematic, out
current implementation blocks generation of valid SPIR-V code for
compute environments. This PR is to implement a solution discussed at
the SPIR-V WG to allow proceeding with generation of valid SPIR-V code
for the OpenCL environment and do not impact Vulkan environment at the
same time.

Author: VyacheslavLevytskyy

llvm/lib/Target/SPIRV/SPIRVModuleAnalysis.cpp

@@ -1723,15 +1723,25 @@ void addInstrRequirements(const MachineInstr &MI,
     Register ImageReg = MI.getOperand(2).getReg();
     SPIRVType *TypeDef = ST.getSPIRVGlobalRegistry()->getResultType(
         ImageReg, const_cast<MachineFunction *>(MI.getMF()));
-    if (isImageTypeWithUnknownFormat(TypeDef))
+    // OpImageRead and OpImageWrite can use Unknown Image Formats
+    // when the Kernel capability is declared. In the OpenCL environment we are
+    // not allowed to produce
+    // StorageImageReadWithoutFormat/StorageImageWriteWithoutFormat, see
+    // https://github.com/KhronosGroup/SPIRV-Headers/issues/487
+    if (isImageTypeWithUnknownFormat(TypeDef) && !ST.isOpenCLEnv())
       Reqs.addCapability(SPIRV::Capability::StorageImageReadWithoutFormat);
     break;
   }
   case SPIRV::OpImageWrite: {
     Register ImageReg = MI.getOperand(0).getReg();
     SPIRVType *TypeDef = ST.getSPIRVGlobalRegistry()->getResultType(
         ImageReg, const_cast<MachineFunction *>(MI.getMF()));
-    if (isImageTypeWithUnknownFormat(TypeDef))
+    // OpImageRead and OpImageWrite can use Unknown Image Formats
+    // when the Kernel capability is declared. In the OpenCL environment we are
+    // not allowed to produce
+    // StorageImageReadWithoutFormat/StorageImageWriteWithoutFormat, see
+    // https://github.com/KhronosGroup/SPIRV-Headers/issues/487
+    if (isImageTypeWithUnknownFormat(TypeDef) && !ST.isOpenCLEnv())
       Reqs.addCapability(SPIRV::Capability::StorageImageWriteWithoutFormat);
     break;
   }

llvm/test/CodeGen/SPIRV/read_image.ll

@@ -1,6 +1,13 @@
 ; RUN: llc -O0 -mtriple=spirv64-unknown-unknown %s -o - | FileCheck %s --check-prefix=CHECK-SPIRV
 
-; CHECK-SPIRV: OpCapability StorageImageReadWithoutFormat
+; StorageImageReadWithoutFormat/StorageImageWriteWithoutFormat implicitly
+; declare Shader, causing a SPIR-V module to be rejected by the OpenCL
+; run-time. See https://github.com/KhronosGroup/SPIRV-Headers/issues/487
+; De-facto, OpImageRead and OpImageWrite are allowed to use Unknown Image
+; Formats when the Kernel capability is declared. We reflect this behavior
+; in the test case, and leave the check under CHECK-SPIRV-NOT to track
+; the issue and follow-up its final resolution when ready.
+; CHECK-SPIRV-NOT: OpCapability StorageImageReadWithoutFormat
 
 ; CHECK-SPIRV: %[[#IntTy:]] = OpTypeInt
 ; CHECK-SPIRV: %[[#IVecTy:]] = OpTypeVector %[[#IntTy]]

llvm/test/CodeGen/SPIRV/transcoding/OpImageReadMS.ll

@@ -1,6 +1,14 @@
 ; RUN: llc -O0 -mtriple=spirv32-unknown-unknown %s -o - | FileCheck %s --check-prefix=CHECK-SPIRV
 
-; CHECK-SPIRV: OpCapability StorageImageReadWithoutFormat
+; StorageImageReadWithoutFormat/StorageImageWriteWithoutFormat implicitly
+; declare Shader, causing a SPIR-V module to be rejected by the OpenCL
+; run-time. See https://github.com/KhronosGroup/SPIRV-Headers/issues/487
+; De-facto, OpImageRead and OpImageWrite are allowed to use Unknown Image
+; Formats when the Kernel capability is declared. We reflect this behavior
+; in the test case, and leave the check under CHECK-SPIRV-NOT to track
+; the issue and follow-up its final resolution when ready.
+; CHECK-SPIRV-NOT: OpCapability StorageImageReadWithoutFormat
+
 ; CHECK-SPIRV: %[[#]] = OpImageRead %[[#]] %[[#]] %[[#]] Sample %[[#]]
 
 define spir_kernel void @sample_test(target("spirv.Image", void, 1, 0, 0, 1, 0, 0, 0) %source, i32 %sampler, <4 x float> addrspace(1)* nocapture %results) {