Remove global fences for integrated graphics.

Global fences are not needed for integra. Runtime already disabled
support for global fence allocation for integra. This commit implements
the change compiler side.

Author: smilczek

IGC/Compiler/CISACodeGen/Platform.hpp

@@ -774,6 +774,22 @@ bool supportsZEBin() const
     }
 }
 
+
+bool isIntegratedGraphics() const
+{
+    switch (m_platformInfo.eProductFamily)
+    {
+    case IGFX_DG1:
+    case IGFX_XE_HP_SDV:
+    case IGFX_DG2:
+    case IGFX_PVC:
+    case IGFX_BMG:
+        return false;
+    default:
+        return true;
+    }
+}
+
 bool loosenSimd32occu() const
 {
     if (IGC_GET_FLAG_VALUE(ForceLoosenSimd32Occu) == 2)

IGC/Compiler/Optimizer/OpenCLPasses/LSCFuncs/LSCFuncsResolution.cpp

@@ -87,7 +87,7 @@ namespace {
         Instruction* CreateSubGroup2DBlockOperation(llvm::CallInst& CI, llvm::StringRef funcName, bool isRead);
 
         /// LSC Fence intrinsics call method
-        Instruction* CreateLSCFenceIntrinsicCallInst();
+        Instruction* CreateLSCFenceIntrinsicCallInst(CallInst& CI);
 
         Instruction* CreateLSCFenceEvictToMemory();
 
@@ -176,6 +176,7 @@ namespace {
         CodeGenContext* m_pCtx = nullptr;
         CallInst* m_pCurrInst = nullptr;
         Function* m_pCurrInstFunc = nullptr;
+        std::set<Instruction*> m_instsToErase{};
 
         // For verifying address payload for block 2d read/write.
         llvm::SmallVector<Instruction *, 32> m_lsc2dblock_readwrite;
@@ -278,6 +279,11 @@ bool LSCFuncsResolution::runOnFunction(Function &F)
 
     visit(F);
 
+    for (auto* inst : m_instsToErase) {
+        inst->eraseFromParent();
+    }
+    m_instsToErase.clear();
+
     verifyBlock2DAddressPayload();
 
     if (hasError()) {
@@ -388,7 +394,7 @@ void LSCFuncsResolution::visitCallInst(CallInst &CI)
     }
     else if (FN.startswith(LSCFuncsResolution::PREFIX_LSC_FENCE)) {
         // LSC fence
-        lscCall = CreateLSCFenceIntrinsicCallInst();
+        lscCall = CreateLSCFenceIntrinsicCallInst(CI);
     } else {
         // not an LSC message, bail silently
         return;
@@ -404,7 +410,7 @@ void LSCFuncsResolution::visitCallInst(CallInst &CI)
     if (lscCall != nullptr) {
         lscCall->setDebugLoc(CI.getDebugLoc());
         CI.replaceAllUsesWith(lscCall);
-        CI.eraseFromParent();
+        m_instsToErase.insert(&CI);
 
         m_changed = true;
     }
@@ -1454,7 +1460,7 @@ Instruction* LSCFuncsResolution::CreateLSCStoreCmaskIntrinsicCallInst(
     return lscCall;
 }
 
-Instruction* LSCFuncsResolution::CreateLSCFenceIntrinsicCallInst() {
+Instruction* LSCFuncsResolution::CreateLSCFenceIntrinsicCallInst(CallInst& CI) {
     LSC_SFID memPort = decodeSfidFromName();
 
     auto context = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();
@@ -1479,6 +1485,12 @@ Instruction* LSCFuncsResolution::CreateLSCFenceIntrinsicCallInst() {
 
     if (scope && (scope->getZExtValue() == LSC_SCOPE_SYSACQ || scope->getZExtValue() == LSC_SCOPE_SYSREL))
     {
+        if (context->platform.isIntegratedGraphics() || context->platform.isCoreXE2())
+        {
+            // Global memory fences are not needed on integrated devices or on Xe2 platforms.
+            m_instsToErase.insert(&CI);
+            return nullptr;
+        }
         if (!context->platform.supportSystemFence())
         {
             reportError("platform does not support system fence");

IGC/Compiler/tests/LSCFuncsResolution/remove_global_fence_for_integra_and_xe2.ll

@@ -0,0 +1,32 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2025 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+;
+; REQUIRES: llvm-14-plus
+; RUN: igc_opt --opaque-pointers --igc-lsc-funcs-translation -platformmtl -S < %s 2>&1 | FileCheck %s
+; ------------------------------------------------
+; LSCFuncsResolution
+; ------------------------------------------------
+
+; Test checks lsc global fences are removed for integra and XE2 platforms.
+
+define spir_kernel void @test_lsc(ptr %base) {
+; CHECK-NOT:    call void @llvm.genx.GenISA.LSCFence
+; CHECK-NOT:    call spir_func void @__builtin_IB_lsc_fence_global
+;
+  call spir_func void @__builtin_IB_lsc_fence_global_untyped(i32 6, i32 1)
+  ret void
+}
+
+declare void @__builtin_IB_lsc_fence_global_untyped(i32, i32)
+
+!igc.functions = !{!0}
+
+!0 = !{ptr @test_lsc, !1}
+!1 = !{!2, !3}
+!2 = !{!"function_type", i32 0}
+!3 = !{!"sub_group_size", i32 16}