JIT: fix permute node type in AVX simd sum

In `gtNewSimdSumNode` we need to type permute nodes as `simd16`, not the sum's type.
If we split the tree at the permute we spill to the wrong typed temp.

Also provide the ability to halt stress tree splitting after some number of splits.

Fixes dotnet#102335.

src/coreclr/jit/compiler.cpp

@@ -5701,12 +5701,20 @@ void Compiler::SplitTreesRandomly()
     rng.Init(info.compMethodHash() ^ 0x077cc4d4);
 
     // Splitting creates a lot of new locals. Set a limit on how many we end up creating here.
-    unsigned maxLvaCount = max(lvaCount * 2, 50000u);
+    unsigned  maxLvaCount = max(lvaCount * 2, 50000u);
+    int       numSplit    = 0;
+    const int splitLimit  = JitConfig.JitStressSplitTreeLimit();
 
     for (BasicBlock* block : Blocks())
     {
         for (Statement* stmt : block->NonPhiStatements())
         {
+            if ((splitLimit >= 0) && (numSplit >= splitLimit))
+            {
+                JITDUMP("Reached split limit (%d) -- stopping\n", splitLimit);
+                return;
+            }
+
             int numTrees = 0;
             for (GenTree* tree : stmt->TreeList())
             {
@@ -5739,6 +5747,7 @@ void Compiler::SplitTreesRandomly()
 
                         fgMorphStmtBlockOps(block, stmt);
                         gtUpdateStmtSideEffects(stmt);
+                        numSplit++;
                     }
 
                     break;
@@ -5754,6 +5763,9 @@ void Compiler::SplitTreesRandomly()
             }
         }
     }
+
+    JITDUMP("Split %d trees\n", numSplit);
+
 #endif
 }
 

src/coreclr/jit/gentree.cpp

@@ -26307,13 +26307,13 @@ GenTree* Compiler::gtNewSimdSumNode(var_types type, GenTree* op1, CorInfoType si
             {
                 assert(compIsaSupportedDebugOnly(InstructionSet_AVX));
                 // The permute below gives us  [0, 1, 2, 3] -> [1, 0, 3, 2]
-                op1 = gtNewSimdHWIntrinsicNode(type, op1, gtNewIconNode((int)0b10110001, TYP_INT), NI_AVX_Permute,
+                op1 = gtNewSimdHWIntrinsicNode(TYP_SIMD16, op1, gtNewIconNode((int)0b10110001, TYP_INT), NI_AVX_Permute,
                                                simdBaseJitType, simdSize);
                 // The add below now results in [0 + 1, 1 + 0, 2 + 3, 3 + 2]
                 op1         = gtNewSimdBinOpNode(GT_ADD, TYP_SIMD16, op1, op1Shuffled, simdBaseJitType, simdSize);
                 op1Shuffled = fgMakeMultiUse(&op1);
                 // The permute below gives us  [0 + 1, 1 + 0, 2 + 3, 3 + 2] -> [2 + 3, 3 + 2, 0 + 1, 1 + 0]
-                op1 = gtNewSimdHWIntrinsicNode(type, op1, gtNewIconNode((int)0b01001110, TYP_INT), NI_AVX_Permute,
+                op1 = gtNewSimdHWIntrinsicNode(TYP_SIMD16, op1, gtNewIconNode((int)0b01001110, TYP_INT), NI_AVX_Permute,
                                                simdBaseJitType, simdSize);
             }
             else
@@ -26345,7 +26345,7 @@ GenTree* Compiler::gtNewSimdSumNode(var_types type, GenTree* op1, CorInfoType si
             {
                 assert(compIsaSupportedDebugOnly(InstructionSet_AVX));
                 // The permute below gives us  [0, 1] -> [1, 0]
-                op1 = gtNewSimdHWIntrinsicNode(type, op1, gtNewIconNode((int)0b0001, TYP_INT), NI_AVX_Permute,
+                op1 = gtNewSimdHWIntrinsicNode(TYP_SIMD16, op1, gtNewIconNode((int)0b0001, TYP_INT), NI_AVX_Permute,
                                                simdBaseJitType, simdSize);
             }
             else

src/coreclr/jit/jitconfigvalues.h

@@ -190,6 +190,9 @@ CONFIG_INTEGER(JitStressProcedureSplitting, W("JitStressProcedureSplitting"), 0)
 CONFIG_INTEGER(JitStressRegs, W("JitStressRegs"), 0)
 CONFIG_STRING(JitStressRegsRange, W("JitStressRegsRange")) // Only apply JitStressRegs to methods in this hash range
 
+// If non-negative value N, only stress split the first N trees.
+CONFIG_INTEGER(JitStressSplitTreeLimit, W("JitStressSplitTreeLimit"), -1)
+
 // If non-zero, assert if # of VNF_MapSelect applications considered reaches this.
 CONFIG_INTEGER(JitVNMapSelLimit, W("JitVNMapSelLimit"), 0)