[llvm] [SPIR-V] Emit Alignment decoration for alloca instructions (PR #118520)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Vyacheslav Levytskyy (VyacheslavLevytskyy)

<details>
<summary>Changes</summary>

The SPIR-V Backend didn't generate Alignment decoration for alloca instructions. This PR is to fix this.

---
Full diff: https://github.com/llvm/llvm-project/pull/118520.diff


3 Files Affected:

- (modified) llvm/include/llvm/IR/IntrinsicsSPIRV.td (+2-2) 
- (modified) llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp (+6-3) 
- (modified) llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp (+23-12) 


``````````diff
diff --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
index 17b70062e58fa9..1ae3129774e507 100644
--- a/llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -36,8 +36,8 @@ let TargetPrefix = "spv" in {
   def int_spv_selection_merge : Intrinsic<[], [llvm_vararg_ty]>;
   def int_spv_cmpxchg : Intrinsic<[llvm_i32_ty], [llvm_any_ty, llvm_vararg_ty]>;
   def int_spv_unreachable : Intrinsic<[], []>;
-  def int_spv_alloca : Intrinsic<[llvm_any_ty], []>;
-  def int_spv_alloca_array : Intrinsic<[llvm_any_ty], [llvm_anyint_ty]>;
+  def int_spv_alloca : Intrinsic<[llvm_any_ty], [llvm_i8_ty], [ImmArg<ArgIndex<0>>]>;
+  def int_spv_alloca_array : Intrinsic<[llvm_any_ty], [llvm_anyint_ty, llvm_i8_ty], [ImmArg<ArgIndex<1>>]>;
   def int_spv_undef : Intrinsic<[llvm_i32_ty], []>;
   def int_spv_inline_asm : Intrinsic<[], [llvm_metadata_ty, llvm_metadata_ty, llvm_vararg_ty]>;
 
diff --git a/llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp b/llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
index f45bdfc7aacb72..7e8c669e676fb5 100644
--- a/llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
@@ -1713,9 +1713,12 @@ Instruction *SPIRVEmitIntrinsics::visitAllocaInst(AllocaInst &I) {
   TrackConstants = false;
   Type *PtrTy = I.getType();
   auto *NewI =
-      ArraySize ? B.CreateIntrinsic(Intrinsic::spv_alloca_array,
-                                    {PtrTy, ArraySize->getType()}, {ArraySize})
-                : B.CreateIntrinsic(Intrinsic::spv_alloca, {PtrTy}, {});
+      ArraySize
+          ? B.CreateIntrinsic(Intrinsic::spv_alloca_array,
+                              {PtrTy, ArraySize->getType()},
+                              {ArraySize, B.getInt8(I.getAlign().value())})
+          : B.CreateIntrinsic(Intrinsic::spv_alloca, {PtrTy},
+                              {B.getInt8(I.getAlign().value())});
   replaceAllUsesWithAndErase(B, &I, NewI);
   return NewI;
 }
diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 3547ac66430a87..3a98b74b3d6757 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -3298,12 +3298,17 @@ bool SPIRVInstructionSelector::selectAllocaArray(Register ResVReg,
   // there was an allocation size parameter to the allocation instruction
   // that is not 1
   MachineBasicBlock &BB = *I.getParent();
-  return BuildMI(BB, I, I.getDebugLoc(),
-                 TII.get(SPIRV::OpVariableLengthArrayINTEL))
-      .addDef(ResVReg)
-      .addUse(GR.getSPIRVTypeID(ResType))
-      .addUse(I.getOperand(2).getReg())
-      .constrainAllUses(TII, TRI, RBI);
+  bool Res = BuildMI(BB, I, I.getDebugLoc(),
+                     TII.get(SPIRV::OpVariableLengthArrayINTEL))
+                 .addDef(ResVReg)
+                 .addUse(GR.getSPIRVTypeID(ResType))
+                 .addUse(I.getOperand(2).getReg())
+                 .constrainAllUses(TII, TRI, RBI);
+  if (!STI.isVulkanEnv()) {
+    unsigned Alignment = I.getOperand(3).getImm();
+    buildOpDecorate(ResVReg, I, TII, SPIRV::Decoration::Alignment, {Alignment});
+  }
+  return Res;
 }
 
 bool SPIRVInstructionSelector::selectFrameIndex(Register ResVReg,
@@ -3312,12 +3317,18 @@ bool SPIRVInstructionSelector::selectFrameIndex(Register ResVReg,
   // Change order of instructions if needed: all OpVariable instructions in a
   // function must be the first instructions in the first block
   auto It = getOpVariableMBBIt(I);
-  return BuildMI(*It->getParent(), It, It->getDebugLoc(),
-                 TII.get(SPIRV::OpVariable))
-      .addDef(ResVReg)
-      .addUse(GR.getSPIRVTypeID(ResType))
-      .addImm(static_cast<uint32_t>(SPIRV::StorageClass::Function))
-      .constrainAllUses(TII, TRI, RBI);
+  bool Res = BuildMI(*It->getParent(), It, It->getDebugLoc(),
+                     TII.get(SPIRV::OpVariable))
+                 .addDef(ResVReg)
+                 .addUse(GR.getSPIRVTypeID(ResType))
+                 .addImm(static_cast<uint32_t>(SPIRV::StorageClass::Function))
+                 .constrainAllUses(TII, TRI, RBI);
+  if (!STI.isVulkanEnv()) {
+    unsigned Alignment = I.getOperand(2).getImm();
+    buildOpDecorate(ResVReg, *It, TII, SPIRV::Decoration::Alignment,
+                    {Alignment});
+  }
+  return Res;
 }
 
 bool SPIRVInstructionSelector::selectBranch(MachineInstr &I) const {

``````````

</details>


https://github.com/llvm/llvm-project/pull/118520