[SPIRV] Additional fixes for const init via UtoPtr

[AlexVlx]

#166494 added support for using inttoptr in global initialisation, and lowering int into OpSpecConstantOp OpConvertUToPtr. Unfortunately, it slightly more subtle case / exposed an existing issue around the COPY pseudo-op. This patch ensures that we glance through a COPY when figuring out whether an OpConvertUToPtr is actually operating on a global. We also correctly handle the case where a G_PTR_ADD is used by an OpSpecConstantOp in the context of global initialisation, which would otherwise lead to broken SPIR-V wherein the latter would reference a non constant Op.

[llvmbot]

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

Author: Alex Voicu (AlexVlx)

Changes

#166494 added support for using inttoptr in global initialisation, and lowering int into OpSpecConstantOp OpConvertUToPtr. Unfortunately, it slightly more subtle case / exposed an existing issue around the COPY pseudo-op. This patch ensures that we glance through a COPY when figuring out whether an OpConvertUToPtr is actually operating on a global. We also correctly handle the case where a G_PTR_ADD is used by an OpSpecConstantOp in the context of global initialisation, which would otherwise lead to broken SPIR-V wherein the latter would reference a non constant Op.

---

Full diff: https://github.com/llvm/llvm-project/pull/172584.diff

2 Files Affected:

• (modified) llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp (+4-3)
• (modified) llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll (+2-1)

diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 2e4563795e8f0..aae025602b763 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -1099,6 +1099,7 @@ bool SPIRVInstructionSelector::spvSelect(Register ResVReg,
              UseEnd = MRI->use_instr_end();
          UseIt != UseEnd; UseIt = std::next(UseIt)) {
       if ((*UseIt).getOpcode() == TargetOpcode::G_GLOBAL_VALUE ||
+          (*UseIt).getOpcode() == SPIRV::OpSpecConstantOp ||
           (*UseIt).getOpcode() == SPIRV::OpVariable) {
         IsGVInit = true;
         break;
@@ -1407,9 +1408,9 @@ bool SPIRVInstructionSelector::selectUnOp(Register ResVReg,
              MRI->def_instr_begin(SrcReg);
          DefIt != MRI->def_instr_end(); DefIt = std::next(DefIt)) {
       unsigned DefOpCode = DefIt->getOpcode();
-      if (DefOpCode == SPIRV::ASSIGN_TYPE) {
-        // We need special handling to look through the type assignment and see
-        // if this is a constant or a global
+      if (DefOpCode == SPIRV::ASSIGN_TYPE || DefOpCode == TargetOpcode::COPY) {
+        // We need special handling to look through the type assignment or the
+        // COPY pseudo-op and see if this is a constant or a global
         if (auto *VRD = getVRegDef(*MRI, DefIt->getOperand(1).getReg()))
           DefOpCode = VRD->getOpcode();
       }
diff --git a/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll b/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll
index f397030c7bdb1..23aaa5573a83c 100644
--- a/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll
+++ b/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll
@@ -12,11 +12,11 @@
 ; CHECK: %[[VtblTy:[0-9]+]] = OpTypeStruct %[[ArrTy]] %[[ArrTy]] %[[ArrTy]] %[[ArrTy]] %[[ArrTy]]
 ; CHECK: %[[Int64Ty:[0-9]+]] = OpTypeInt 64 0
 ; CHECK: %[[GlobVtblPtrTy:[0-9]+]] = OpTypePointer CrossWorkgroup %[[VtblTy]]
+; CHECK: %[[Const184:[0-9]+]] = OpConstant %[[Int64Ty]] 184
 ; CHECK: %[[ConstMinus184:[0-9]+]] = OpConstant %[[Int64Ty]] 18446744073709551432
 ; CHECK: %[[ConstMinus16:[0-9]+]] = OpConstant %[[Int64Ty]] 18446744073709551600
 ; CHECK: %[[Const168:[0-9]+]] = OpConstant %[[Int64Ty]] 168
 ; CHECK: %[[Nullptr:[0-9]+]] = OpConstantNull %[[GlobInt8PtrTy]]
-; CHECK: %[[Const184:[0-9]+]] = OpConstant %[[Int64Ty]] 184
 ; CHECK: %[[Const184toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[Const184]]
 ; CHECK: %[[Const168toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[Const168]]
 ; CHECK: %[[ConstMinus16toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[ConstMinus16]]
@@ -33,6 +33,7 @@
                                                             [5 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 184 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null],
                                                             [5 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 168 to ptr addrspace(1)), ptr addrspace(1) inttoptr (i64 -16 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null],
                                                             [5 x ptr addrspace(1)] [ptr addrspace(1) inttoptr (i64 -184 to ptr addrspace(1)), ptr addrspace(1) inttoptr (i64 -184 to ptr addrspace(1)), ptr addrspace(1) null, ptr addrspace(1) null, ptr addrspace(1) null] }
+@VTT = linkonce_odr unnamed_addr addrspace(1) constant [1 x ptr addrspace(1)][ptr addrspace(1) getelementptr inbounds inrange(-24, 16) ({ [5 x ptr addrspace(1)], [5 x ptr addrspace(1)], [5 x ptr addrspace(1)], [5 x ptr addrspace(1)], [5 x ptr addrspace(1)] }, ptr addrspace(1) @vtable, i32 0, i32 4, i32 3)]
 
 define linkonce_odr spir_func void @foo(ptr addrspace(4) %this) {
 entry: