[clang] [HLSL][DirectX] Fix resource lowering when using structs with `select` (PR #158361)

[Kaitlin Peng via cfe-commits]

https://github.com/kmpeng created https://github.com/llvm/llvm-project/pull/158361

Fixes #156550.

The `select` instruction should be using the struct values themselves rather than pointers to temporary allocas.


>From feb15ecf6bd0f956564e7c892dabc419f7094214 Mon Sep 17 00:00:00 2001
From: kmpeng <kaitlinpeng at microsoft.com>
Date: Wed, 3 Sep 2025 17:45:03 -0700
Subject: [PATCH] fix select codegen

---
 clang/lib/CodeGen/CGHLSLBuiltins.cpp        | 4 ++--
 clang/test/CodeGenHLSL/builtins/select.hlsl | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/clang/lib/CodeGen/CGHLSLBuiltins.cpp b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
index 5004c09e0d5cf..7b5b924b1fe82 100644
--- a/clang/lib/CodeGen/CGHLSLBuiltins.cpp
+++ b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
@@ -604,12 +604,12 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
     Value *OpTrue =
         RValTrue.isScalar()
             ? RValTrue.getScalarVal()
-            : RValTrue.getAggregatePointer(E->getArg(1)->getType(), *this);
+            : Builder.CreateLoad(RValTrue.getAggregateAddress(), "true_val");
     RValue RValFalse = EmitAnyExpr(E->getArg(2));
     Value *OpFalse =
         RValFalse.isScalar()
             ? RValFalse.getScalarVal()
-            : RValFalse.getAggregatePointer(E->getArg(2)->getType(), *this);
+            : Builder.CreateLoad(RValFalse.getAggregateAddress(), "false_val");
     if (auto *VTy = E->getType()->getAs<VectorType>()) {
       if (!OpTrue->getType()->isVectorTy())
         OpTrue =
diff --git a/clang/test/CodeGenHLSL/builtins/select.hlsl b/clang/test/CodeGenHLSL/builtins/select.hlsl
index 196b8a90cd877..a5a398af44646 100644
--- a/clang/test/CodeGenHLSL/builtins/select.hlsl
+++ b/clang/test/CodeGenHLSL/builtins/select.hlsl
@@ -11,8 +11,10 @@ int test_select_bool_int(bool cond0, int tVal, int fVal) {
 
 struct S { int a; };
 // CHECK-LABEL: test_select_infer
-// CHECK: [[SELECT:%.*]] = select i1 {{%.*}}, ptr {{%.*}}, ptr {{%.*}}
-// CHECK: store ptr [[SELECT]]
+// CHECK: [[TRUE_VAL:%.*]] = load %struct.S, ptr {{%.*}}, align 1
+// CHECK: [[FALSE_VAL:%.*]] = load %struct.S, ptr {{%.*}}, align 1
+// CHECK: [[SELECT:%.*]] = select i1 {{%.*}}, %struct.S [[TRUE_VAL]], %struct.S [[FALSE_VAL]]
+// CHECK: store %struct.S [[SELECT]], ptr {{%.*}}, align 1
 // CHECK: ret void
 struct S test_select_infer(bool cond0, struct S tVal, struct S fVal) {
   return select(cond0, tVal, fVal);