[Wasm RyuJit] throw helper / null check preliminaries

src/coreclr/jit/codegenwasm.cpp

@@ -13,10 +13,14 @@
 static const instruction INS_I_const = INS_i64_const;
 static const instruction INS_I_add   = INS_i64_add;
 static const instruction INS_I_sub   = INS_i64_sub;
+static const instruction INS_I_le_u  = INS_i64_le_u;
+static const instruction INS_I_gt_u  = INS_i64_gt_u;
 #else  // !TARGET_64BIT
 static const instruction INS_I_const = INS_i32_const;
 static const instruction INS_I_add   = INS_i32_add;
 static const instruction INS_I_sub   = INS_i32_sub;
+static const instruction INS_I_le_u  = INS_i32_le_u;
+static const instruction INS_I_gt_u  = INS_i32_gt_u;
 #endif // !TARGET_64BIT
 
 void CodeGen::genMarkLabelsForCodegen()
@@ -495,6 +499,10 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             genCodeForNegNot(treeNode->AsOp());
             break;
 
+        case GT_NULLCHECK:
+            genCodeForNullCheck(treeNode->AsIndir());
+            break;
+
         case GT_IND:
             genCodeForIndir(treeNode->AsIndir());
             break;
@@ -922,6 +930,37 @@ void CodeGen::genCodeForDivMod(GenTreeOp* treeNode)
 {
     genConsumeOperands(treeNode);
 
+    // wasm stack is
+    // divisor (top)
+    // dividend (next)
+    // ...
+    // TODO-WASM: To check for exception, we will have to spill these to
+    // internal registers along the way, like so:
+    //
+    // ... push dividend
+    // tee.local $temp1
+    // ... push divisor
+    // tee.local $temp2
+    // ... exception checks (using $temp1 and $temp2; will introduce flow)
+    // div/mod op
+
+    if (!varTypeIsFloating(treeNode->TypeGet()))
+    {
+        ExceptionSetFlags exSetFlags = treeNode->OperExceptions(compiler);
+
+        // TODO-WASM:(AnyVal / 0) => DivideByZeroException
+        //
+        if ((exSetFlags & ExceptionSetFlags::DivideByZeroException) != ExceptionSetFlags::None)
+        {
+        }
+
+        // TODO-WASM: (MinInt / -1) => ArithmeticException
+        //
+        if ((exSetFlags & ExceptionSetFlags::ArithmeticException) != ExceptionSetFlags::None)
+        {
+        }
+    }
+
     instruction ins;
     switch (PackOperAndType(treeNode->OperGet(), treeNode->TypeGet()))
     {
@@ -1136,6 +1175,48 @@ void CodeGen::genCodeForNegNot(GenTreeOp* tree)
     genProduceReg(tree);
 }
 
+//---------------------------------------------------------------------
+// genCodeForNullCheck - generate code for a GT_NULLCHECK node
+//
+// Arguments:
+//    tree - the GT_NULLCHECK node
+//
+// Notes:
+//    If throw helper calls are being emitted inline, we need
+//    to wrap the resulting codegen in a block/end pair.
+//
+void CodeGen::genCodeForNullCheck(GenTreeIndir* tree)
+{
+    genConsumeAddress(tree->Addr());
+
+    // TODO-WASM: refactor once we have implemented other cases invoking throw helpers
+    if (compiler->fgUseThrowHelperBlocks())
+    {
+        Compiler::AddCodeDsc* const add = compiler->fgFindExcptnTarget(SCK_NULL_CHECK, compiler->compCurBB);
+
+        if (add == nullptr)
+        {
+            NYI_WASM("Missing null check demand");
+        }
+
+        assert(add != nullptr);
+        assert(add->acdUsed);
+        GetEmitter()->emitIns_I(INS_I_const, EA_PTRSIZE, compiler->compMaxUncheckedOffsetForNullObject);
+        GetEmitter()->emitIns(INS_I_le_u);
+        inst_JMP(EJ_jmpif, add->acdDstBlk);
+    }
+    else
+    {
+        GetEmitter()->emitIns_I(INS_I_const, EA_PTRSIZE, compiler->compMaxUncheckedOffsetForNullObject);
+        GetEmitter()->emitIns(INS_I_le_u);
+        GetEmitter()->emitIns(INS_if);
+        // TODO-WASM: codegen for the call instead of unreachable
+        // genEmitHelperCall(compiler->acdHelper(SCK_NULL_CHECK), 0, EA_UNKNOWN);
+        GetEmitter()->emitIns(INS_unreachable);
+        GetEmitter()->emitIns(INS_end);
+    }
+}
+
 //------------------------------------------------------------------------
 // genCodeForLclAddr: Generates the code for GT_LCL_ADDR.
 //

src/coreclr/jit/compiler.cpp

@@ -438,6 +438,15 @@ Compiler::Compiler(ArenaAllocator*       arena,
 
     compMaxUncheckedOffsetForNullObject = eeInfo->maxUncheckedOffsetForNullObject;
 
+#if defined(DEBUG) && defined(TARGET_WASM)
+    // TODO-WASM: remove once we no longer need to use x86/arm collections for wasm replay
+    // if we are cross-replaying wasm, override compMaxUncheckedOffsetForNullObject
+    if (!info.compMatchedVM)
+    {
+        compMaxUncheckedOffsetForNullObject = 1024 - 1;
+    }
+#endif
+
     info.compProfilerCallback = false; // Assume false until we are told to hook this method.
 
     info.compCode         = methodInfo->ILCode;

src/coreclr/jit/compiler.h

@@ -2841,7 +2841,15 @@ class Compiler
 #endif // DEBUG
 
     bool     ehAnyFunclets();  // Are there any funclets in this function?
-    unsigned ehFuncletCount(); // Return the count of funclets in the function
+    unsigned ehFuncletCount(); // Return the count of funclets in the function.
+
+#ifdef TARGET_WASM
+    // Once we have run wasm layout, try regions may no longer be contiguous.
+    //
+    bool fgTrysNotContiguous() { return fgIndexToBlockMap != nullptr; }
+#else
+    bool fgTrysNotContiguous() { return false; }
+#endif
 
     FlowEdge* BlockPredsWithEH(BasicBlock* blk);
     FlowEdge* BlockDominancePreds(BasicBlock* blk);

src/coreclr/jit/fgwasm.cpp

@@ -107,9 +107,13 @@ FlowGraphDfsTree* FgWasm::WasmDfs(bool& hasBlocksOnlyReachableViaEH)
     JITDUMP("Determining Wasm DFS entry points\n");
 
     // All funclets are entries. For now we assume finallys are funclets.
+    // We walk from outer->inner order, so that for mutual protect trys
+    // the "first" handler is visited last and ends up earlier in RPO.
     //
-    for (EHblkDsc* const ehDsc : EHClauses(comp))
+    for (int XTnum = comp->compHndBBtabCount - 1; XTnum >= 0; XTnum--)
     {
+        EHblkDsc* const ehDsc = &comp->compHndBBtab[XTnum];
+
         JITDUMP(FMT_BB " is handler entry\n", ehDsc->ebdHndBeg->bbNum);
         entryBlocks.push_back(ehDsc->ebdHndBeg);
         if (ehDsc->HasFilter())
@@ -1390,6 +1394,17 @@ PhaseStatus Compiler::fgWasmControlFlow()
         {
             fgUnlinkBlock(block);
             fgInsertBBafter(lastBlock, block);
+
+            // If the last block was the end of a handler, we may need
+            // to update the enclosing region endpoint.
+            //
+            // Because we are not keeping try regions contiguous,
+            // we can't and don't need to do the same for a try.
+            //
+            if (ehIsBlockHndLast(lastBlock) && block->hasHndIndex() && BasicBlock::sameHndRegion(lastBlock, block))
+            {
+                fgSetHndEnd(ehGetBlockHndDsc(block), block);
+            }
             lastBlock = block;
         }
 
@@ -1441,6 +1456,11 @@ PhaseStatus Compiler::fgWasmControlFlow()
     JITDUMPEXEC(fgDumpWasmControlFlow());
     JITDUMPEXEC(fgDumpWasmControlFlowDot());
 
+    // By publishing the index to block map, we are also indicating
+    // that try regions may no longer be contiguous.
+    //
+    assert(fgTrysNotContiguous());
+
     return PhaseStatus::MODIFIED_EVERYTHING;
 }
 

src/coreclr/jit/fgwasm.h

@@ -318,9 +318,51 @@ class FgWasm
 //  consider exceptional successors or successors that require runtime intervention
 //  (eg funclet returns).
 //
+// For method and funclet entries we add any "ACD" blocks as successors before the
+// true successors. This ensures the ACD blocks end up at the end of the funclet
+// region, and that we create proper Wasm blocks so we can branch to them from
+// anywhere within the method region or funclet region.
+//
 template <typename TFunc>
 BasicBlockVisit FgWasm::VisitWasmSuccs(Compiler* comp, BasicBlock* block, TFunc func, bool useProfile)
 {
+    // Special case throw helper blocks that are not yet connected in the flow graph.
+    //
+    Compiler::AddCodeDscMap* const acdMap = comp->fgGetAddCodeDscMap();
+    if (acdMap != nullptr)
+    {
+        // Behave as if these blocks have edges from their respective region entry blocks.
+        //
+        if ((block == comp->fgFirstBB) || comp->bbIsFuncletBeg(block))
+        {
+            Compiler::AcdKeyDesignator dsg;
+            const unsigned             blockData = comp->bbThrowIndex(block, &dsg);
+
+            // We do not expect any ACDs to be mapped to try regions (only method/handler/filter)
+            //
+            assert(dsg != Compiler::AcdKeyDesignator::KD_TRY);
+
+            for (const Compiler::AddCodeDscKey& key : Compiler::AddCodeDscMap::KeyIteration(acdMap))
+            {
+                if (key.Data() == blockData)
+                {
+                    // This ACD refers to a throw helper block in the right region.
+                    // Make the block a successor.
+                    //
+                    Compiler::AddCodeDsc* acd = nullptr;
+                    acdMap->Lookup(key, &acd);
+
+                    // We only need to consider used ACDs... we may have demanded throw helpers that are not needed.
+                    //
+                    if (acd->acdUsed)
+                    {
+                        RETURN_ON_ABORT(func(acd->acdDstBlk));
+                    }
+                }
+            }
+        }
+    }
+
     switch (block->GetKind())
     {
         // Funclet returns have no successors

src/coreclr/jit/flowgraph.cpp

@@ -3326,6 +3326,8 @@ unsigned Compiler::acdHelper(SpecialCodeKind codeKind)
             return CORINFO_HELP_OVERFLOW;
         case SCK_FAIL_FAST:
             return CORINFO_HELP_FAIL_FAST;
+        case SCK_NULL_CHECK:
+            return CORINFO_HELP_THROWNULLREF;
         default:
             assert(!"Bad codeKind");
             return 0;
@@ -3358,6 +3360,8 @@ const char* sckName(SpecialCodeKind codeKind)
             return "SCK_ARITH_EXCPN";
         case SCK_FAIL_FAST:
             return "SCK_FAIL_FAST";
+        case SCK_NULL_CHECK:
+            return "SCK_NULL_CHECK";
         default:
             return "SCK_UNKNOWN";
     }
@@ -3490,6 +3494,7 @@ PhaseStatus Compiler::fgCreateThrowHelperBlocks()
         BBJ_THROW,  // SCK_ARG_EXCPN
         BBJ_THROW,  // SCK_ARG_RNG_EXCPN
         BBJ_THROW,  // SCK_FAIL_FAST
+        BBJ_THROW,  // SCK_NULL_CHECK
     };
 
     noway_assert(sizeof(jumpKinds) == SCK_COUNT); // sanity check
@@ -3555,6 +3560,9 @@ PhaseStatus Compiler::fgCreateThrowHelperBlocks()
                 case SCK_FAIL_FAST:
                     msg = " for FAIL_FAST";
                     break;
+                case SCK_NULL_CHECK:
+                    msg = " for NULL_CHECK";
+                    break;
                 default:
                     msg = " for ??";
                     break;
@@ -3676,7 +3684,13 @@ Compiler::AddCodeDsc* Compiler::fgFindExcptnTarget(SpecialCodeKind kind, BasicBl
         {
             JITDUMP(FMT_BB ": unexpected request for new throw helper: kind %d (%s), data 0x%08x\n", fromBlock->bbNum,
                     kind, sckName(kind), key.Data());
+
+            if (kind == SCK_NULL_CHECK)
+            {
+                NYI_WASM("Missing null check demand");
+            }
         }
+
         assert(!fgRngChkThrowAdded);
     }
 
@@ -3708,13 +3722,28 @@ unsigned Compiler::bbThrowIndex(BasicBlock* blk, AcdKeyDesignator* dsg)
 
     assert(inTry || inHnd);
 
+#if defined(TARGET_WASM)
+    // The current plan for Wasm: method regions or funclets with
+    // trys will have a single Wasm try handle all
+    // resumption from catches via virtual IPs.
+    //
+    // So we do not need to consider the nesting of the throw
+    // in try regions, just in handlers.
+    //
+    if (!inHnd)
+    {
+        *dsg = AcdKeyDesignator::KD_NONE;
+        return 0;
+    }
+#else
     if (inTry && (!inHnd || (tryIndex < hndIndex)))
     {
         // The most enclosing region is a try body, use it
         assert(tryIndex <= 0x3FFFFFFF);
         *dsg = AcdKeyDesignator::KD_TRY;
         return tryIndex;
     }
+#endif // !defined(TARGET_WASM)
 
     // The most enclosing region is a handler which will be a funclet
     // Now we have to figure out if blk is in the filter or handler
@@ -3731,7 +3760,7 @@ unsigned Compiler::bbThrowIndex(BasicBlock* blk, AcdKeyDesignator* dsg)
 }
 
 //------------------------------------------------------------------------
-// AddCodedDscKey: construct from kind and block
+// AddCodeDscKey: construct from kind and block
 //
 // Arguments:
 //    kind - exception kind
@@ -3755,7 +3784,7 @@ Compiler::AddCodeDscKey::AddCodeDscKey(SpecialCodeKind kind, BasicBlock* block,
 }
 
 //------------------------------------------------------------------------
-// AddCodedDscKey: construct from AddCodeDsc
+// AddCodeDscKey: construct from AddCodeDsc
 //
 // Arguments:
 //    add - add code dsc in querstion

src/coreclr/jit/gentree.h

@@ -62,6 +62,7 @@ enum SpecialCodeKind
     SCK_ARG_EXCPN,                  // target on ArgumentException (currently used only for SIMD intrinsics)
     SCK_ARG_RNG_EXCPN,              // target on ArgumentOutOfRangeException (currently used only for SIMD intrinsics)
     SCK_FAIL_FAST,                  // target for fail fast exception
+    SCK_NULL_CHECK,                 // target for NullReferenceException (Wasm)
     SCK_COUNT
 };
 

src/coreclr/jit/jiteh.cpp

@@ -3695,7 +3695,7 @@ void Compiler::fgVerifyHandlerTab()
     // Make sure that all blocks have the right index, including those blocks that should have zero (no EH region).
     for (BasicBlock* const block : Blocks())
     {
-        assert(block->bbTryIndex == blockTryIndex[block->bbNum]);
+        assert(fgTrysNotContiguous() || block->bbTryIndex == blockTryIndex[block->bbNum]);
         assert(block->bbHndIndex == blockHndIndex[block->bbNum]);
 
         // Also, since we're walking the blocks, check that all blocks we didn't mark as EH handler 'begin' blocks

src/coreclr/jit/stacklevelsetter.cpp

@@ -273,6 +273,13 @@ void StackLevelSetter::SetThrowHelperBlocks(GenTree* node, BasicBlock* block)
         break;
 #endif
 
+#if defined(TARGET_WASM)
+        // TODO-WASM: add other opers that imply null checks
+        case GT_NULLCHECK:
+            SetThrowHelperBlock(SCK_NULL_CHECK, block);
+            break;
+#endif // defined(TARGET_WASM)
+
         default: // Other opers can target throw only due to overflow.
             break;
     }

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -3394,8 +3394,19 @@ private void getEEInfo(ref CORINFO_EE_INFO pEEInfoOut)
 
             pEEInfoOut.osPageSize = 0x1000;
 
-            pEEInfoOut.maxUncheckedOffsetForNullObject = (_compilation.NodeFactory.Target.IsWindows) ?
-                (32 * 1024 - 1) : (pEEInfoOut.osPageSize / 2 - 1);
+            if (_compilation.NodeFactory.Target.IsWasm)
+            {
+                // TODO: Set this value to 0 for Wasm
+                pEEInfoOut.maxUncheckedOffsetForNullObject = 1024 - 1;
+            }
+            else if (_compilation.NodeFactory.Target.IsWindows)
+            {
+                pEEInfoOut.maxUncheckedOffsetForNullObject = 32 * 1024 - 1;
+            }
+            else
+            {
+                pEEInfoOut.maxUncheckedOffsetForNullObject = pEEInfoOut.osPageSize / 2 - 1;
+            }
 
             pEEInfoOut.targetAbi = TargetABI;
             pEEInfoOut.osType = TargetToOs(_compilation.NodeFactory.Target);