[SPIRV] Handle `inttoptr` constant expressions in global initialisers #166494

AlexVlx · 2025-11-05T03:06:50Z

inttoptr usage in global initialisers is valid, and rather common when it comes to the machinery around vtables (construction vtables are particularly fond). This was not handled by the BE, even though SPIR-V allows forming SpecConstantOps with the OpConvertUToPtr opcode, which is what these would map to. We augment instruction selection to address this.

llvmbot · 2025-11-05T03:07:23Z

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

Author: Alex Voicu (AlexVlx)

Changes

inttoptr usage in global initialisers is valid, and rather common when it comes to the machinery around vtables (construction vtables are particularly fond). This was not handled by the BE, even though SPIR-V allows forming SpecConstantOps with the OpConvertUToPtr opcode, which is what these would map to. We augment instruction selection to address this.

Full diff: https://github.com/llvm/llvm-project/pull/166494.diff

3 Files Affected:

(modified) llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp (+13-3)
(modified) llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp (+11)
(added) llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll (+49)

diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 3f0424f436c72..b00b6bd164421 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -1210,8 +1210,17 @@ bool SPIRVInstructionSelector::selectUnOp(Register ResVReg,
     for (MachineRegisterInfo::def_instr_iterator DefIt =
              MRI->def_instr_begin(SrcReg);
          DefIt != MRI->def_instr_end(); DefIt = std::next(DefIt)) {
-      if ((*DefIt).getOpcode() == TargetOpcode::G_GLOBAL_VALUE ||
-          (*DefIt).getOpcode() == SPIRV::OpVariable) {
+      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 (auto *VRD = getVRegDef(*MRI, (*DefIt).getOperand(1).getReg()))
+          DefOpCode = VRD->getOpcode();
+      }
+      if (DefOpCode == TargetOpcode::G_GLOBAL_VALUE ||
+          DefOpCode == TargetOpcode::G_CONSTANT ||
+          DefOpCode == SPIRV::OpVariable ||
+          DefOpCode == SPIRV::OpConstantI) {
         IsGV = true;
         break;
       }
@@ -3099,9 +3108,10 @@ bool SPIRVInstructionSelector::wrapIntoSpecConstantOp(
     SmallPtrSet<SPIRVType *, 4> Visited;
     if (!OpDefine || !OpType || isConstReg(MRI, OpDefine, Visited) ||
         OpDefine->getOpcode() == TargetOpcode::G_ADDRSPACE_CAST ||
+        OpDefine->getOpcode() == TargetOpcode::G_INTTOPTR ||
         GR.isAggregateType(OpType)) {
       // The case of G_ADDRSPACE_CAST inside spv_const_composite() is processed
-      // by selectAddrSpaceCast()
+      // by selectAddrSpaceCast(), and G_INTTOPTR is processed by selectUnOp()
       CompositeArgs.push_back(OpReg);
       continue;
     }
diff --git a/llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp b/llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp
index d538009f0ecbe..128403a646787 100644
--- a/llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp
@@ -348,6 +348,16 @@ static SPIRVType *propagateSPIRVType(MachineInstr *MI, SPIRVGlobalRegistry *GR,
         SpvType = GR->getOrCreateSPIRVIntegerType(
             MRI.getType(Reg).getScalarSizeInBits(), MIB);
         break;
+      case TargetOpcode::G_INTTOPTR:
+        // With opaque pointers it doesn't appear as if we can convert to
+        // anything but a pointer to i8
+        SpvType = GR->getOrCreateSPIRVPointerType(
+            GR->getOrCreateSPIRVIntegerType(8, MIB),
+            MIB,
+            addressSpaceToStorageClass(
+                MRI.getType(Reg).getAddressSpace(),
+                MIB.getMF().getSubtarget<SPIRVSubtarget>()));
+        break;
       case TargetOpcode::G_TRUNC:
       case TargetOpcode::G_ADDRSPACE_CAST:
       case TargetOpcode::G_PTR_ADD:
@@ -684,6 +694,7 @@ generateAssignInstrs(MachineFunction &MF, SPIRVGlobalRegistry *GR,
       case TargetOpcode::G_SEXT:
       case TargetOpcode::G_ZEXT:
       case TargetOpcode::G_PTRTOINT:
+      case TargetOpcode::G_INTTOPTR:
       case TargetOpcode::COPY:
       case TargetOpcode::G_ADDRSPACE_CAST:
         propagateSPIRVType(&MI, GR, MRI, MIB);
diff --git a/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll b/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll
new file mode 100644
index 0000000000000..614c126e02656
--- /dev/null
+++ b/llvm/test/CodeGen/SPIRV/transcoding/ConvertPtrInGlobalInit.ll
@@ -0,0 +1,49 @@
+; 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: %[[Int8Ty:[0-9]+]] = OpTypeInt 8 0
+; CHECK: %[[Int8PtrTy:[0-9]+]] = OpTypePointer Generic %[[Int8Ty]]
+; CHECK-DAG: %[[GlobInt8PtrTy:[0-9]+]] = OpTypePointer CrossWorkgroup %[[Int8Ty]]
+; CHECK: %[[GlobInt8PtrPtrTy:[0-9]+]] = OpTypePointer CrossWorkgroup %[[GlobInt8PtrTy]]
+; CHECK: %[[Int8PtrGlobPtrPtrTy:[0-9]+]] = OpTypePointer Generic %[[GlobInt8PtrPtrTy]]
+; CHECK: %[[Int32Ty:[0-9]+]] = OpTypeInt 32 0
+; CHECK: %[[Const5:[0-9]+]] = OpConstant %[[Int32Ty]] 5
+; CHECK: %[[ArrTy:[0-9]+]] = OpTypeArray %[[GlobInt8PtrTy]] %[[Const5]]
+; 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: %[[ConstMinus184:[0-9]+]] = OpConstant %[[Int64Ty]] 18446744073709551432
+; CHECK: %[[ConstMinus16:[0-9]+]] = OpConstant %[[Int64Ty]] 18446744073709551600
+; CHECK: %[[Const168:[0-9]+]] = OpConstant %[[Int64Ty]] 168
+; CHECK: %[[Const184:[0-9]+]] = OpConstant %[[Int64Ty]] 184
+; CHECK: %[[Nullptr:[0-9]+]] = OpConstantNull %[[GlobInt8PtrTy]]
+; CHECK: %[[Const184toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[Const184]]
+; CHECK: %[[Const168toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[Const168]]
+; CHECK: %[[ConstMinus16toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[ConstMinus16]]
+; CHECK: %[[ConstMinus184toPtr:[0-9]+]] = OpSpecConstantOp %[[GlobInt8PtrTy]] ConvertUToPtr %[[ConstMinus184]]
+; CHECK: %[[Vtbl012:[0-9]+]] = OpConstantComposite %[[ArrTy]] %[[Const184toPtr]] %[[Nullptr]] %[[Nullptr]] %[[Nullptr]] %[[Nullptr]]
+; CHECK: %[[Vtbl3:[0-9]+]] = OpConstantComposite %[[ArrTy]] %[[Const168toPtr]] %[[ConstMinus16toPtr]] %[[Nullptr]] %[[Nullptr]] %[[Nullptr]]
+; CHECK: %[[Vtbl4:[0-9]+]] = OpConstantComposite %[[ArrTy]] %[[ConstMinus184toPtr]] %[[ConstMinus184toPtr]] %[[Nullptr]] %[[Nullptr]] %[[Nullptr]]
+; CHECK: %[[Vtbl:[0-9]+]] = OpConstantComposite %[[VtblTy]] %[[Vtbl012]] %[[Vtbl012]] %[[Vtbl012]] %[[Vtbl3]] %[[Vtbl4]]
+; CHECK: %[[#]] = OpVariable %[[GlobVtblPtrTy]] CrossWorkgroup %[[Vtbl]]
+
+@vtable = linkonce_odr unnamed_addr addrspace(1) constant { [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)] }
+                                                          { [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 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 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] }
+
+define linkonce_odr spir_func void @foo(ptr addrspace(4) %this) {
+entry:
+  %0 = getelementptr inbounds i8, ptr addrspace(4) %this, i64 184
+  store 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 0, i32 3), ptr addrspace(4) %this
+  store 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 1, i32 3), ptr addrspace(4) %this
+  store 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 2, i32 3), ptr addrspace(4) %this
+  %add.ptr = getelementptr inbounds i8, ptr addrspace(4) %this, i64 184
+  store 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), ptr addrspace(4) %add.ptr
+  %add.ptr2 = getelementptr inbounds i8, ptr addrspace(4) %this, i64 16
+  store 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 3, i32 3), ptr addrspace(4) %add.ptr2
+
+  ret void
+}

github-actions · 2025-11-05T03:08:35Z

✅ With the latest revision this PR passed the C/C++ code formatter.

jmmartinez

Just 2 nits.

jmmartinez · 2025-11-05T08:24:32Z

llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp

         DefIt != MRI->def_instr_end(); DefIt = std::next(DefIt)) {
-      if ((*DefIt).getOpcode() == TargetOpcode::G_GLOBAL_VALUE ||
-          (*DefIt).getOpcode() == SPIRV::OpVariable) {
+      unsigned DefOpCode = (*DefIt).getOpcode();


NIT

Suggested change

unsigned DefOpCode = (*DefIt).getOpcode();

unsigned DefOpCode = DefIt->getOpcode();

jmmartinez · 2025-11-05T08:30:01Z

llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp

+      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 (auto *VRD = getVRegDef(*MRI, (*DefIt).getOperand(1).getReg()))


Same NIT as above.

Suggested change

if (auto *VRD = getVRegDef(*MRI, (*DefIt).getOperand(1).getReg()))

if (auto *VRD = getVRegDef(*MRI, DefIt->getOperand(1).getReg()))

…v_staging_6

Keenuts · 2025-11-05T13:13:16Z

llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp

-      if ((*DefIt).getOpcode() == TargetOpcode::G_GLOBAL_VALUE ||
-          (*DefIt).getOpcode() == SPIRV::OpVariable) {
+      unsigned DefOpCode = (*DefIt).getOpcode();
+      if (DefOpCode == SPIRV::ASSIGN_TYPE) {


Isn't this loop only iterating on register definitions and not uses?
I thought spv.assign.type as spv.assign.ptr.type were intrinsics registering as having a side-effect, but returning no values?

The intrinsics get lowered to a pseudo (ASSIGN_TYPE) which defines a destination vreg, which is what gets used by subsequent instructions, rather than the global whose type we assigned; hence the need to have a peek through the type assignment. The sequence looks something like so:

%60:iid(s64) = G_CONSTANT i64 184 %9:iid(s64) = ASSIGN_TYPE %60:iid(s64), %49:type(s64) %8:_(p1) = G_INTTOPTR %9:iid(s64)

I will note that we cannot use the result of the type assignment, as that assigns the from integer's type, and not the to pointer's type.

Keenuts · 2025-11-05T13:14:56Z

llvm/lib/Target/SPIRV/SPIRVPreLegalizer.cpp

            MRI.getType(Reg).getScalarSizeInBits(), MIB);
        break;
+      case TargetOpcode::G_INTTOPTR:
+        // With opaque pointers it doesn't appear as if we can convert to


handling of asssign.ptr.type is done after? Or shall those be used to determine the pointer type of this cast?

I don't think assign.ptr.type works for global values / quantities, as the assumption is that globals are already typeful. Hence the need to give this a type - in some sense it is symmetric with the ptrtoint above. There isn't enough context to infer any type other than void* at this point (these'd essentially be ConstantExprs) - the only operator that'd carry extra type info might be GEP, but it's not immediately apparent how we'd have an inttoptr followed by gep sequence. Apologies if I misunderstood the gist of the question / suggestion or if I'm missing something obvious.

Handle inttoptr constant expressions in global initialisers.

b80da0e

llvmbot added the backend:SPIR-V label Nov 5, 2025

AlexVlx requested review from Keenuts, MrSidims, VyacheslavLevytskyy, jmmartinez, mgcarrasco and michalpaszkowski November 5, 2025 03:07

Fix formatting.

e19b00c

jmmartinez reviewed Nov 5, 2025

View reviewed changes

Merge branch 'main' of https://github.com/llvm/llvm-project into spir…

2cb1153

…v_staging_6

Keenuts reviewed Nov 5, 2025

View reviewed changes

AlexVlx added 4 commits November 5, 2025 14:53

Fix nits.

658d7be

Adapt tests.

9fa3f88

Simplify / remove erroneous impl.

b42433f

Properly do type assignment.

49cab16

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

[SPIRV] Handle `inttoptr` constant expressions in global initialisers #166494

[SPIRV] Handle `inttoptr` constant expressions in global initialisers #166494

AlexVlx commented Nov 5, 2025

Uh oh!

llvmbot commented Nov 5, 2025

Uh oh!

github-actions bot commented Nov 5, 2025 •

edited

Loading

Uh oh!

jmmartinez left a comment

Uh oh!

jmmartinez Nov 5, 2025

Uh oh!

jmmartinez Nov 5, 2025

Uh oh!

Keenuts Nov 5, 2025

Uh oh!

AlexVlx Nov 5, 2025 •

edited

Loading

Uh oh!

Keenuts Nov 5, 2025

Uh oh!

AlexVlx Nov 5, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

	unsigned DefOpCode = (*DefIt).getOpcode();
	unsigned DefOpCode = DefIt->getOpcode();

	if (auto VRD = getVRegDef(MRI, (*DefIt).getOperand(1).getReg()))
	if (auto VRD = getVRegDef(MRI, DefIt->getOperand(1).getReg()))

[SPIRV] Handle inttoptr constant expressions in global initialisers #166494

Are you sure you want to change the base?

[SPIRV] Handle inttoptr constant expressions in global initialisers #166494

Conversation

AlexVlx commented Nov 5, 2025

Uh oh!

llvmbot commented Nov 5, 2025

Uh oh!

github-actions bot commented Nov 5, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

jmmartinez left a comment

Choose a reason for hiding this comment

Uh oh!

jmmartinez Nov 5, 2025

Choose a reason for hiding this comment

Uh oh!

jmmartinez Nov 5, 2025

Choose a reason for hiding this comment

Uh oh!

Keenuts Nov 5, 2025

Choose a reason for hiding this comment

Uh oh!

AlexVlx Nov 5, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Keenuts Nov 5, 2025

Choose a reason for hiding this comment

Uh oh!

AlexVlx Nov 5, 2025

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

[SPIRV] Handle `inttoptr` constant expressions in global initialisers #166494

[SPIRV] Handle `inttoptr` constant expressions in global initialisers #166494

github-actions bot commented Nov 5, 2025 •

edited

Loading

AlexVlx Nov 5, 2025 •

edited

Loading