[SPIR-V] Stop re-writing SPIR-V type map (#3856)

There is a map used during forward translation. It links LLVM type
and SPIR-V type, that is being generated, LLVM type here is used as
a key. Due to a bug in type mapping (information is below), it's
possible that for a single pointer type in LLVM, the translator
will create 2 physically-indentical SPIR-V pointer types and with
previous implementation of mapType function the map would be changed
during the second type insertion. This patch prevents it, forcing
to reuse the type that was created first, though we would still have
an unused duplication of this type in SPIR-V module.

Please consider following LLVM IR sample:
%struct._ZTS4Args.Args = type { %struct._ZTS6Object.Object addrspace(4)* }
%struct._ZTS6Object.Object = type { i32 (%struct._ZTS6Object.Object addrspace(4)*, i32)* }

Here we have 2 LLVM type declarations. The translator will recursively
go through structure members and then through element types of the
pointer types, creating the appropriate SPIR-V types and mapping them
on LLVM types. Due to a recursive nature of this algorithm, here we will
have '%struct._ZTS6Object.Object addrspace(4)*' be processed twice with
2 SPIR-V type declaration instruction being created.

Signed-off-by: Dmitry Sidorov <[email protected]>

Author: MrSidims

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -1793,7 +1793,10 @@ LLVMToSPIRVBase::transValueWithoutDecoration(Value *V, SPIRVBasicBlock *BB,
 }
 
 SPIRVType *LLVMToSPIRVBase::mapType(Type *T, SPIRVType *BT) {
-  TypeMap[T] = BT;
+  auto EmplaceStatus = TypeMap.try_emplace(T, BT);
+  (void)EmplaceStatus;
+  // TODO: Uncomment the assertion, once the type mapping issue is resolved
+  // assert(EmplaceStatus.second && "The type was already added to the map");
   SPIRVDBG(dbgs() << "[mapType] " << *T << " => "; spvdbgs() << *BT << '\n');
   return BT;
 }

llvm-spirv/test/pointer_type_mapping.ll

@@ -0,0 +1,30 @@
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc --spirv-ext=+all -spirv-text -o %t
+; RUN: FileCheck < %t %s
+
+; CHECK: Name [[#NAME:]] "struct._ZTS6Object.Object"
+; CHECK-COUNT-1: TypeStruct [[#NAME]]
+; TODO add check count one and remove unused, when the type mapping bug is fixed
+; CHECK: TypePointer [[#UNUSED:]] {{.*}} [[#NAME]]
+; CHECK: TypePointer [[#PTRTY:]] {{.*}} [[#NAME]]
+; CHECK: FunctionParameter [[#PTRTY]]
+; CHECK-NOT: FunctionParameter [[#UNUSED]]
+
+; ModuleID = 'sycl_test.bc'
+source_filename = "sycl_test.cpp"
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+target triple = "spir64-unknown-unknown-sycldevice"
+
+%struct._ZTS4Args.Args = type { %struct._ZTS6Object.Object addrspace(4)* }
+%struct._ZTS6Object.Object = type { i32 (%struct._ZTS6Object.Object addrspace(4)*, i32)* }
+
+; Function Attrs: convergent norecurse nounwind mustprogress
+define dso_local spir_func i32 @_Z9somefunc0P4Args(%struct._ZTS4Args.Args addrspace(4)* %a, %struct._ZTS6Object.Object addrspace(4)* %b) {
+entry:
+  ret i32 0
+}
+
+!opencl.spir.version = !{!0}
+!spirv.Source = !{!1}
+!0 = !{i32 1, i32 2}
+!1 = !{i32 4, i32 100000}