Fix target id in decorates when there is forward decl (#2606)

When there is forward declaration of a spirv entry, its decorates are
not translated until its definition is seen. Forward id is re-used for
its entry. Id in entry decorates should use forward id as well.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@305f48884606abf

Author: wenju-he

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVEntry.cpp

@@ -386,6 +386,16 @@ void SPIRVEntry::takeAnnotations(SPIRVForward *E) {
     static_cast<SPIRVFunction *>(this)->takeExecutionModes(E);
 }
 
+void SPIRVEntry::replaceTargetIdInDecorates(SPIRVId Id) {
+  for (auto It = Decorates.begin(), E = Decorates.end(); It != E; ++It)
+    const_cast<SPIRVDecorate *>(It->second)->setTargetId(Id);
+  for (auto It = DecorateIds.begin(), E = DecorateIds.end(); It != E; ++It)
+    const_cast<SPIRVDecorateId *>(It->second)->setTargetId(Id);
+  for (auto It = MemberDecorates.begin(), E = MemberDecorates.end(); It != E;
+       ++It)
+    const_cast<SPIRVMemberDecorate *>(It->second)->setTargetId(Id);
+}
+
 // Check if an entry has Kind of decoration and get the literal of the
 // first decoration of such kind at Index.
 bool SPIRVEntry::hasDecorate(Decoration Kind, size_t Index,

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVEntry.h

@@ -371,6 +371,7 @@ class SPIRVEntry {
   void takeDecorates(SPIRVEntry *);
   void takeDecorateIds(SPIRVEntry *);
   void takeMemberDecorates(SPIRVEntry *);
+  void replaceTargetIdInDecorates(SPIRVId);
 
   /// After a SPIRV entry is created during reading SPIRV binary by default
   /// constructor, this function is called to allow the SPIRV entry to resize

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVModule.cpp

@@ -1176,17 +1176,19 @@ SPIRVEntry *SPIRVModuleImpl::replaceForward(SPIRVForward *Forward,
                                             SPIRVEntry *Entry) {
   SPIRVId Id = Entry->getId();
   SPIRVId ForwardId = Forward->getId();
-  if (ForwardId == Id)
+  if (ForwardId == Id) {
     IdEntryMap[Id] = Entry;
-  else {
+    // Annotations include name, decorations, execution modes
+    Entry->takeAnnotations(Forward);
+  } else {
     auto Loc = IdEntryMap.find(Id);
     assert(Loc != IdEntryMap.end());
     IdEntryMap.erase(Loc);
     Entry->setId(ForwardId);
     IdEntryMap[ForwardId] = Entry;
+    // Replace current Id with ForwardId in decorates.
+    Entry->replaceTargetIdInDecorates(ForwardId);
   }
-  // Annotations include name, decorations, execution modes
-  Entry->takeAnnotations(Forward);
   delete Forward;
   return Entry;
 }

llvm-spirv/test/transcoding/decoration-forward-decl.ll

@@ -0,0 +1,39 @@
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc -spirv-text -o - | FileCheck %s --check-prefix=CHECK-SPIRV
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefix=CHECK-LLVM
+
+; Check saturation conversion is translated when there is forward declaration
+; of SPIRV entry.
+
+; CHECK-SPIRV: Decorate [[SAT:[0-9]+]] SaturatedConversion
+; CHECK-SPIRV: ConvertFToU {{[0-9]+}} [[SAT]]
+
+; CHECK-LLVM: convert_uchar_satf
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-G1"
+target triple = "spir64"
+
+declare spir_func zeroext i8 @_Z30__spirv_ConvertFToU_Ruchar_satf(float)
+
+define spir_func void @forward(float %val, ptr addrspace(1) %dst) {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %new_val.0 = phi i8 [ undef, %entry ], [ %call1, %for.body ]
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %cmp = icmp ult i32 %i.0, 1
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %call1 = call spir_func zeroext i8 @_Z30__spirv_ConvertFToU_Ruchar_satf(float noundef %val)
+  %inc = add i32 %i.0, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  store i8 %new_val.0, ptr addrspace(1) %dst, align 1
+  ret void
+}