[SPIR-V] Ensure that internal intrinsic functions "ptrcast" for PHI's operand are inserted at the correct positions (#92536)

The goal of the PR is to ensure that newly inserted `ptrcast` internal
intrinsic functions are inserted at the correct positions, and don't
break rules of instruction domination and PHI nodes grouping at top of
basic block.

Author: VyacheslavLevytskyy

llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp

@@ -489,17 +489,15 @@ void SPIRVEmitIntrinsics::deduceOperandElementType(Instruction *I) {
     Type *Ty = GR->findDeducedElementType(Op);
     if (Ty == KnownElemTy)
       continue;
-    if (Instruction *User = dyn_cast<Instruction>(Op->use_begin()->get()))
-      setInsertPointSkippingPhis(B, User->getNextNode());
-    else
-      setInsertPointSkippingPhis(B, I);
     Value *OpTyVal = Constant::getNullValue(KnownElemTy);
     Type *OpTy = Op->getType();
     if (!Ty) {
       GR->addDeducedElementType(Op, KnownElemTy);
       // check if there is existing Intrinsic::spv_assign_ptr_type instruction
       auto It = AssignPtrTypeInstr.find(Op);
       if (It == AssignPtrTypeInstr.end()) {
+        Instruction *User = dyn_cast<Instruction>(Op->use_begin()->get());
+        setInsertPointSkippingPhis(B, User ? User->getNextNode() : I);
         CallInst *CI =
             buildIntrWithMD(Intrinsic::spv_assign_ptr_type, {OpTy}, OpTyVal, Op,
                             {B.getInt32(getPointerAddressSpace(OpTy))}, B);
@@ -511,6 +509,17 @@ void SPIRVEmitIntrinsics::deduceOperandElementType(Instruction *I) {
                 Ctx, MDNode::get(Ctx, ValueAsMetadata::getConstant(OpTyVal))));
       }
     } else {
+      if (auto *OpI = dyn_cast<Instruction>(Op)) {
+        // spv_ptrcast's argument Op denotes an instruction that generates
+        // a value, and we may use getInsertionPointAfterDef()
+        B.SetInsertPoint(*OpI->getInsertionPointAfterDef());
+        B.SetCurrentDebugLocation(OpI->getDebugLoc());
+      } else if (auto *OpA = dyn_cast<Argument>(Op)) {
+        B.SetInsertPointPastAllocas(OpA->getParent());
+        B.SetCurrentDebugLocation(DebugLoc());
+      } else {
+        B.SetInsertPoint(F->getEntryBlock().getFirstNonPHIOrDbgOrAlloca());
+      }
       SmallVector<Type *, 2> Types = {OpTy, OpTy};
       MetadataAsValue *VMD = MetadataAsValue::get(
           Ctx, MDNode::get(Ctx, ValueAsMetadata::getConstant(OpTyVal)));

llvm/test/CodeGen/SPIRV/phi-ptrcast-dominate.ll

@@ -0,0 +1,94 @@
+; The goal of the test is to check that newly inserted `ptrcast` internal
+; intrinsic functions for PHI's operands are inserted at the correct
+; positions, and don't break rules of instruction domination and PHI nodes
+; grouping at top of basic block.
+
+; 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-DAG: OpName %[[#Case1:]] "case1"
+; CHECK-DAG: OpName %[[#Case2:]] "case2"
+; CHECK-DAG: OpName %[[#Case3:]] "case3"
+; CHECK: %[[#Case1]] = OpFunction
+; CHECK: OpBranchConditional
+; CHECK: OpPhi
+; CHECK: OpBranch
+; CHECK-COUNT-2: OpBranchConditional
+; CHECK: OpFunctionEnd
+; CHECK: %[[#Case2]] = OpFunction
+; CHECK: OpBranchConditional
+; CHECK: OpPhi
+; CHECK: OpBranch
+; CHECK-COUNT-2: OpBranchConditional
+; CHECK: OpFunctionEnd
+; CHECK: %[[#Case3]] = OpFunction
+; CHECK: OpBranchConditional
+; CHECK: OpPhi
+; CHECK: OpBranch
+; CHECK: OpInBoundsPtrAccessChain
+; CHECK: OpBranchConditional
+; CHECK: OpInBoundsPtrAccessChain
+; CHECK: OpBranchConditional
+; CHECK: OpFunctionEnd
+
+%struct1 = type { i64 }
+%struct2 = type { i64, i64 }
+
+@.str.1 = private unnamed_addr addrspace(1) constant [3 x i8] c"OK\00", align 1
+@.str.2 = private unnamed_addr addrspace(1) constant [6 x i8] c"WRONG\00", align 1
+
+define spir_func void @case1(i1 %b1, i1 %b2, i1 %b3) {
+entry:
+  br i1 %b1, label %l1, label %l2
+
+l1:
+  %str = phi ptr addrspace(1) [ @.str.1, %entry ], [ @.str.2, %l2 ], [ @.str.2, %l3 ]
+  br label %exit
+
+l2:
+  br i1 %b2, label %l1, label %l3
+
+l3:
+  br i1 %b3, label %l1, label %exit
+
+exit:
+  ret void
+}
+
+define spir_func void @case2(i1 %b1, i1 %b2, i1 %b3, ptr addrspace(1) byval(%struct1) %str1, ptr addrspace(1) byval(%struct2) %str2) {
+entry:
+  br i1 %b1, label %l1, label %l2
+
+l1:
+  %str = phi ptr addrspace(1) [ %str1, %entry ], [ %str2, %l2 ], [ %str2, %l3 ]
+  br label %exit
+
+l2:
+  br i1 %b2, label %l1, label %l3
+
+l3:
+  br i1 %b3, label %l1, label %exit
+
+exit:
+  ret void
+}
+
+define spir_func void @case3(i1 %b1, i1 %b2, i1 %b3, ptr addrspace(1) byval(%struct1) %_arg_str1, ptr addrspace(1) byval(%struct2) %_arg_str2) {
+entry:
+  br i1 %b1, label %l1, label %l2
+
+l1:
+  %str = phi ptr addrspace(1) [ %_arg_str1, %entry ], [ %str2, %l2 ], [ %str3, %l3 ]
+  br label %exit
+
+l2:
+  %str2 = getelementptr inbounds %struct2, ptr addrspace(1) %_arg_str2, i32 1
+  br i1 %b2, label %l1, label %l3
+
+l3:
+  %str3 = getelementptr inbounds %struct2, ptr addrspace(1) %_arg_str2, i32 2
+  br i1 %b3, label %l1, label %exit
+
+exit:
+  ret void
+}