JIT: Avoid resolving def-use conflicts by changing use registers

src/coreclr/jit/codegen.h

@@ -1139,6 +1139,7 @@ class CodeGen final : public CodeGenInterface
     void genCodeForShiftRMW(GenTreeStoreInd* storeInd);
 #endif // TARGET_XARCH
 
+    void genCodeForCatchArg(GenTree* tree);
     void genCodeForCast(GenTreeOp* tree);
     void genCodeForLclAddr(GenTreeLclFld* lclAddrNode);
     void genCodeForIndexAddr(GenTreeIndexAddr* tree);

src/coreclr/jit/codegenarmarch.cpp

@@ -500,14 +500,7 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             break;
 
         case GT_CATCH_ARG:
-
-            noway_assert(handlerGetsXcptnObj(m_compiler->compCurBB->GetCatchType()));
-
-            /* Catch arguments get passed in a register. genCodeForBBlist()
-               would have marked it as holding a GC object, but not used. */
-
-            noway_assert(gcInfo.gcRegGCrefSetCur & RBM_EXCEPTION_OBJECT);
-            genConsumeReg(treeNode);
+            genCodeForCatchArg(treeNode);
             break;
 
         case GT_ASYNC_CONTINUATION:

src/coreclr/jit/codegenlinear.cpp

@@ -1471,7 +1471,7 @@ void CodeGen::genCheckConsumeNode(GenTree* const node)
         }
     }
 
-    assert(node->OperIs(GT_CATCH_ARG) || ((node->gtDebugFlags & GTF_DEBUG_NODE_CG_CONSUMED) == 0));
+    assert((node->gtDebugFlags & GTF_DEBUG_NODE_CG_CONSUMED) == 0);
     assert((lastConsumedNode == nullptr) || (node->gtUseNum == -1) || (node->gtUseNum > lastConsumedNode->gtUseNum));
 
     node->gtDebugFlags |= GTF_DEBUG_NODE_CG_CONSUMED;
@@ -2334,6 +2334,30 @@ void CodeGen::genTransferRegGCState(regNumber dst, regNumber src)
 }
 #endif
 
+//------------------------------------------------------------------------
+// genCodeForCatchArg:
+//   Generates code for GT_CATCH_ARG.
+//
+// Arguments:
+//    tree - the GT_CATCH_ARG node.
+//
+void CodeGen::genCodeForCatchArg(GenTree* tree)
+{
+    noway_assert(handlerGetsXcptnObj(m_compiler->compCurBB->GetCatchType()));
+
+    // Catch arguments get passed in a register. genCodeForBBlist()
+    // would have marked it as holding a GC object, but not used.
+
+    noway_assert(gcInfo.gcRegGCrefSetCur & RBM_EXCEPTION_OBJECT);
+    inst_Mov(TYP_REF, tree->GetRegNum(), REG_EXCEPTION_OBJECT, /* canSkip */ true);
+
+    if (tree->GetRegNum() != REG_EXCEPTION_OBJECT)
+    {
+        gcInfo.gcMarkRegSetNpt(RBM_EXCEPTION_OBJECT);
+    }
+    genProduceReg(tree);
+}
+
 //------------------------------------------------------------------------
 // genCodeForCast: Generates the code for GT_CAST.
 //

src/coreclr/jit/codegenloongarch64.cpp

@@ -4371,14 +4371,7 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             break;
 
         case GT_CATCH_ARG:
-
-            noway_assert(handlerGetsXcptnObj(m_compiler->compCurBB->GetCatchType()));
-
-            /* Catch arguments get passed in a register. genCodeForBBlist()
-               would have marked it as holding a GC object, but not used. */
-
-            noway_assert(gcInfo.gcRegGCrefSetCur & RBM_EXCEPTION_OBJECT);
-            genConsumeReg(treeNode);
+            genCodeForCatchArg(treeNode);
             break;
 
         case GT_LABEL:

src/coreclr/jit/codegenriscv64.cpp

@@ -4158,14 +4158,7 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             break;
 
         case GT_CATCH_ARG:
-
-            noway_assert(handlerGetsXcptnObj(m_compiler->compCurBB->GetCatchType()));
-
-            /* Catch arguments get passed in a register. genCodeForBBlist()
-               would have marked it as holding a GC object, but not used. */
-
-            noway_assert(gcInfo.gcRegGCrefSetCur & RBM_EXCEPTION_OBJECT);
-            genConsumeReg(treeNode);
+            genCodeForCatchArg(treeNode);
             break;
 
         case GT_LABEL:

src/coreclr/jit/codegenxarch.cpp

@@ -752,7 +752,6 @@ void CodeGen::genCodeForMulHi(GenTreeOp* treeNode)
         // Move the result to the desired register, if necessary
         if (treeNode->OperIs(GT_MULHI))
         {
-            assert(targetReg == REG_RDX);
             inst_Mov(targetType, targetReg, REG_RDX, /* canSkip */ true);
         }
     }
@@ -2109,14 +2108,7 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             break;
 
         case GT_CATCH_ARG:
-
-            noway_assert(handlerGetsXcptnObj(m_compiler->compCurBB->GetCatchType()));
-
-            /* Catch arguments get passed in a register. genCodeForBBlist()
-               would have marked it as holding a GC object, but not used. */
-
-            noway_assert(gcInfo.gcRegGCrefSetCur & RBM_EXCEPTION_OBJECT);
-            genConsumeReg(treeNode);
+            genCodeForCatchArg(treeNode);
             break;
 
         case GT_ASYNC_CONTINUATION:
@@ -4389,9 +4381,6 @@ void CodeGen::genLockedInstructions(GenTreeOp* node)
             // When value is used (it's the original value of the memory location)
             // we fallback to cmpxchg-loop idiom.
 
-            // for cmpxchg we need to keep the original value in RAX
-            assert(node->GetRegNum() == REG_RAX);
-
             //    mov     RAX, dword ptr [addrReg]
             //.LOOP:
             //    mov     tmp, RAX
@@ -4415,6 +4404,8 @@ void CodeGen::genLockedInstructions(GenTreeOp* node)
             inst_JMP(EJ_jne, loop);
 
             gcInfo.gcMarkRegSetNpt(genRegMask(addr->GetRegNum()));
+            inst_Mov(node->TypeGet(), node->GetRegNum(), REG_RAX, /* canSkip */ true);
+
             genProduceReg(node);
         }
         return;

src/coreclr/jit/lsra.cpp

@@ -11052,29 +11052,20 @@ void LinearScan::dumpLsraAllocationEvent(LsraDumpEvent event,
             printf("DUconflict    ");
             dumpRegRecords();
             break;
-        case LSRA_EVENT_DEFUSE_CASE1:
-            printf(indentFormat, "  Case #1 use defRegAssignment");
+        case LSRA_EVENT_DEFUSE_DEF_IN_FIXED_USE:
+            printf(indentFormat, "  Define in fixed use reg");
             dumpRegRecords();
             break;
-        case LSRA_EVENT_DEFUSE_CASE2:
-            printf(indentFormat, "  Case #2 use useRegAssignment");
+        case LSRA_EVENT_DEFUSE_DEF_IN_USE:
+            printf(indentFormat, "  Define in candidate use reg");
             dumpRegRecords();
             break;
-        case LSRA_EVENT_DEFUSE_CASE3:
-            printf(indentFormat, "  Case #3 use useRegAssignment");
-            dumpRegRecords();
-            dumpRegRecords();
-            break;
-        case LSRA_EVENT_DEFUSE_CASE4:
-            printf(indentFormat, "  Case #4 use defRegAssignment");
-            dumpRegRecords();
-            break;
-        case LSRA_EVENT_DEFUSE_CASE5:
-            printf(indentFormat, "  Case #5 set def to all regs");
+        case LSRA_EVENT_DEFUSE_ANY_DEF:
+            printf(indentFormat, "  Define in any reg");
             dumpRegRecords();
             break;
-        case LSRA_EVENT_DEFUSE_CASE6:
-            printf(indentFormat, "  Case #6 need a copy");
+        case LSRA_EVENT_DEFUSE_COPY:
+            printf(indentFormat, "  Need a copy");
             dumpRegRecords();
             if (interval == nullptr)
             {
@@ -11247,7 +11238,6 @@ void LinearScan::dumpLsraAllocationEvent(LsraDumpEvent event,
             break;
 
         // We currently don't dump anything for these events.
-        case LSRA_EVENT_DEFUSE_FIXED_DELAY_USE:
         case LSRA_EVENT_SPILL_EXTENDED_LIFETIME:
         case LSRA_EVENT_END_BB:
         case LSRA_EVENT_FREE_REGS:

src/coreclr/jit/lsra.h

@@ -1523,13 +1523,10 @@ class LinearScan : public RegAllocInterface
     {
         // Conflicting def/use
         LSRA_EVENT_DEFUSE_CONFLICT,
-        LSRA_EVENT_DEFUSE_FIXED_DELAY_USE,
-        LSRA_EVENT_DEFUSE_CASE1,
-        LSRA_EVENT_DEFUSE_CASE2,
-        LSRA_EVENT_DEFUSE_CASE3,
-        LSRA_EVENT_DEFUSE_CASE4,
-        LSRA_EVENT_DEFUSE_CASE5,
-        LSRA_EVENT_DEFUSE_CASE6,
+        LSRA_EVENT_DEFUSE_DEF_IN_FIXED_USE,
+        LSRA_EVENT_DEFUSE_DEF_IN_USE,
+        LSRA_EVENT_DEFUSE_ANY_DEF,
+        LSRA_EVENT_DEFUSE_COPY,
 
         // Spilling
         LSRA_EVENT_SPILL,