Redesign the frame layout for LoongArch64 to avoid the redundant computation of the stackOffsets.

After the `lvaAssignVirtualFrameOffsetsToLocals`,
there is no need to recompute the LclVarDsc's StackOffset within the `lvaFixVirtualFrameOffsets`.

Author: shushanhf

src/coreclr/jit/codegen.h

@@ -442,7 +442,6 @@ class CodeGen final : public CodeGenInterface
         int fiFunction_CallerSP_to_FP_delta; // Delta between caller SP and the frame pointer in the parent function
                                              // (negative)
         int fiSP_to_CalleeSaved_delta;       // CalleeSaved register save offset from SP (positive)
-        int fiCalleeSavedPadding;            // CalleeSaved offset padding (positive)
         int fiSP_to_PSP_slot_delta;          // PSP slot offset from SP (positive)
         int fiCallerSP_to_PSP_slot_delta;    // PSP slot offset from Caller SP (negative)
         int fiSpDelta;                       // Stack pointer delta (negative)
@@ -1281,7 +1280,6 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     void genJmpMethod(GenTree* jmp);
     BasicBlock* genCallFinally(BasicBlock* block);
 #if defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV64)
-    // TODO: refactor for LA.
     void genCodeForJumpCompare(GenTreeOpCC* tree);
 #endif
 #if defined(TARGET_ARM64)

src/coreclr/jit/codegencommon.cpp

@@ -4922,7 +4922,7 @@ void CodeGen::genEnregisterOSRArgsAndLocals()
 
         GetEmitter()->emitIns_R_AR(ins_Load(lclTyp), size, varDsc->GetRegNum(), genFramePointerReg(), offset);
 
-#elif defined(TARGET_ARM64) || defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV64)
+#elif defined(TARGET_ARM64) || defined(TARGET_RISCV64)
 
         // Patchpoint offset is from top of Tier0 frame
         //
@@ -4948,6 +4948,39 @@ void CodeGen::genEnregisterOSRArgsAndLocals()
         //               |         |                |              |
         const int offset = stkOffs + tier0FrameSize + osrFrameSize - osrSpToFpDelta;
 
+        JITDUMP("---OSR--- V%02u (reg) Tier0 virtual offset %d OSR frame size %d OSR sp-fp "
+                "delta %d total offset %d (0x%x)\n",
+                varNum, stkOffs, osrFrameSize, osrSpToFpDelta, offset, offset);
+
+        genInstrWithConstant(ins_Load(lclTyp), size, varDsc->GetRegNum(), genFramePointerReg(), offset, initReg);
+        *pInitRegZeroed = false;
+
+#elif defined(TARGET_LOONGARCH64)
+
+        // Patchpoint offset is from top of Tier0 frame
+        //
+        // We need to determine the frame-pointer relative
+        // offset for this variable in the osr frame.
+        //
+        // First get the fp's relative offset within Tier0 frame
+        //
+        const int tier0FrameOffset = compiler->info.compPatchpointInfo->CalleeSaveRegisters();
+
+        // then add the OSR frame size
+        //
+        const int osrFrameSize = genTotalFrameSize();
+
+        // then subtract OSR SP-FP delta
+        //
+        const int osrSpToFpDelta = genSPtoFPdelta();
+
+        //               | => tier0 top of frame relative
+        //               |         + => tier0's fp relative offset
+        //               |         |                  + => osr bottom of frame (sp) relative
+        //               |         |                  |              - => osr fp relative
+        //               |         |                  |              |
+        const int offset = stkOffs + tier0FrameOffset + osrFrameSize - osrSpToFpDelta;
+
         JITDUMP("---OSR--- V%02u (reg) Tier0 virtual offset %d OSR frame size %d OSR sp-fp "
                 "delta %d total offset %d (0x%x)\n",
                 varNum, stkOffs, osrFrameSize, osrSpToFpDelta, offset, offset);