From 7ded578285caf55198f855bed196f2845921f21b Mon Sep 17 00:00:00 2001
From: Deric Cheung <cheung.deric@gmail.com>
Date: Thu, 18 Jun 2026 11:37:43 -0700
Subject: [PATCH] Set sampler feedback shader flag for DXIL ops

Detect sampler feedback DXIL ops when collecting shader flags and
gate the SamplerFeedback requirement by validator version >= 1.9.
Add an HLSL FileCheck test covering both enabled and gated behavior.

Assisted-by: Claude Opus 4.8
---
 lib/DXIL/DxilShaderFlags.cpp                  |  7 +++++++
 .../FeedbackTexture/feedback_shader_flag.hlsl | 20 +++++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 tools/clang/test/HLSLFileCheck/hlsl/objects/FeedbackTexture/feedback_shader_flag.hlsl

diff --git a/lib/DXIL/DxilShaderFlags.cpp b/lib/DXIL/DxilShaderFlags.cpp
index 71c7305b68..90b7d033b5 100644
--- a/lib/DXIL/DxilShaderFlags.cpp
+++ b/lib/DXIL/DxilShaderFlags.cpp
@@ -586,6 +586,8 @@ ShaderFlags ShaderFlags::CollectShaderFlags(const Function *F,
           continue;
         if (hlsl::OP::IsDxilOpWave(dxilOp))
           hasWaveOps = true;
+        if (hlsl::OP::IsDxilOpFeedback(dxilOp))
+          hasSamplerFeedback = true;
         switch (dxilOp) {
         case DXIL::OpCode::CheckAccessFullyMapped:
           hasCheckAccessFully = true;
@@ -821,6 +823,11 @@ ShaderFlags ShaderFlags::CollectShaderFlags(const Function *F,
     // Before validator version 1.8, RequiresGroup flag did not exist.
     requiresGroup = false;
   }
+  if (hasSamplerFeedback &&
+      DXIL::CompareVersions(valMajor, valMinor, 1, 9) < 0) {
+    // Before validator version 1.9, SamplerFeedback flag was not set.
+    hasSamplerFeedback = false;
+  }
 
   flag.SetEnableDoublePrecision(hasDouble);
   flag.SetStencilRef(hasStencilRef);
diff --git a/tools/clang/test/HLSLFileCheck/hlsl/objects/FeedbackTexture/feedback_shader_flag.hlsl b/tools/clang/test/HLSLFileCheck/hlsl/objects/FeedbackTexture/feedback_shader_flag.hlsl
new file mode 100644
index 0000000000..e3c7378a6b
--- /dev/null
+++ b/tools/clang/test/HLSLFileCheck/hlsl/objects/FeedbackTexture/feedback_shader_flag.hlsl
@@ -0,0 +1,20 @@
+// RUN: %dxc -E main -T ps_6_5 %s | FileCheck %s -check-prefix=FLAG
+// RUN: %dxc -E main -T ps_6_5 -validator-version 1.8 %s | FileCheck %s -check-prefix=NOFLAG
+
+// Verify that the Sampler feedback shader feature flag is set when any
+// sampler feedback instruction is used, and that it is gated off for
+// validator versions before 1.9.
+
+// FLAG: Note: shader requires additional functionality:
+// FLAG: Sampler feedback
+
+// NOFLAG-NOT: Sampler feedback
+
+FeedbackTexture2D<SAMPLER_FEEDBACK_MIN_MIP> feedbackMinMip;
+Texture2D<float> texture2D;
+SamplerState samp;
+
+float main() : SV_Target {
+  feedbackMinMip.WriteSamplerFeedback(texture2D, samp, (float2)0);
+  return 0;
+}