Support more scenarios in ShrinkArrayAlloca

This PR adds support for scenarios that use `InsertElement` instructions.

Author: mmerecki

IGC/Compiler/ShrinkArrayAlloca.cpp

@@ -176,7 +176,7 @@ inline Value* RepackToOldType(
 // - only bitcast, PHI, load, store and extract element instructions are
 //   supported
 inline bool GetUsedVectorElements(
-    Value* parentVal,
+    Value* parentPtr,
     Value* val,
     SmallVector<bool, 4>& used)
 {
@@ -188,6 +188,7 @@ inline bool GetUsedVectorElements(
             // Unsupported alloca use type.
             return false;
         }
+        parentPtr = gepInst;
     }
     else if (ExtractElementInst* ee = dyn_cast<ExtractElementInst>(val))
     {
@@ -230,13 +231,17 @@ inline bool GetUsedVectorElements(
         {
             return false;
         }
+        if (srcTy->isPointerTy())
+        {
+            parentPtr = bc;
+        }
         // Supported bit cast type, check users for extract element
         // instructions.
     }
     else if (StoreInst* store = dyn_cast<StoreInst>(val))
     {
         // This function only needs to check read access.
-        if (store->getPointerOperand() == parentVal)
+        if (store->getPointerOperand() == parentPtr)
         {
             return true;
         }
@@ -247,6 +252,7 @@ inline bool GetUsedVectorElements(
     }
     else if (!(isa<AllocaInst>(val) ||
         isa<PHINode>(val) ||
+        isa<InsertElementInst>(val) ||
         isa<LoadInst>(val)))
     {
         return false;
@@ -255,7 +261,7 @@ inline bool GetUsedVectorElements(
     // Follow the def-use chain
     for (User* user : val->users())
     {
-        if (!GetUsedVectorElements(val, user, used))
+        if (!GetUsedVectorElements(parentPtr, user, used))
         {
             return false;
         }

IGC/Compiler/tests/ShrinkArrayAlloca/vec4-to-scalar-insert.ll

@@ -0,0 +1,37 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2025 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+
+; RUN: igc_opt --typed-pointers %s -S --shrink-array-alloca | FileCheck %s
+;
+
+define float @f0(i32 %index, float %data0) #1 {
+Label-0:
+  %alloca = alloca [64 x <4 x float>], align 16
+  %addr = getelementptr [64 x <4 x float>], [64 x <4 x float>]* %alloca, i32 0, i32 %index
+  %vec0 = load <4 x float>, <4 x float>* %addr
+  %data1 = insertelement <4 x float> %vec0, float %data0, i64 2
+  store <4 x float> %data1, <4 x float>* %addr, align 16
+  %addr1 = getelementptr [64 x <4 x float>], [64 x <4 x float>]* %alloca, i32 0, i32 %index
+  %vec1 = load <4 x float>, <4 x float>* %addr1
+  %a = extractelement <4 x float> %vec1, i64 2
+  ret float %a
+}
+
+; CHECK:        [[ALLOCA:%[A-z0-9]*]] = alloca [64 x float], align 4
+; CHECK:        [[ADDR:%[A-z0-9]*]] = getelementptr [64 x float], [64 x float]* [[ALLOCA]], i32 0, i32 %index
+; CHECK:        [[Z:%[A-z0-9]*]] = load float, float* [[ADDR]], align 4
+; CHECK:        [[VEC0:%[A-z0-9]*]] = insertelement <4 x float> undef, float [[Z]], i64 2
+; CHECK:        [[VEC1:%[A-z0-9]*]] = insertelement <4 x float> [[VEC0]], float %data0, i64 2
+; CHECK:        [[Z:%[A-z0-9]*]] = extractelement <4 x float> [[VEC1]], i64 2
+; CHECK-NEXT:   store float [[Z]], float* [[ADDR]], align 4
+; CHECK:        [[ADDR:%[A-z0-9]*]] = getelementptr [64 x float], [64 x float]* [[ALLOCA]], i32 0, i32 %index
+; CHECK:        [[A:%[A-z0-9]*]] = load float, float* [[ADDR]], align 4
+; CHECK:        ret float [[A]]
+
+attributes #1 = { "null-pointer-is-valid"="true" }
+