From 82418b16a135825e51a2afda3c6a00758615ba27 Mon Sep 17 00:00:00 2001
From: dubiousconst282 <87553666+dubiousconst282@users.noreply.github.com>
Date: Wed, 18 Jun 2025 21:13:29 -0300
Subject: Always emit DepthReplacing execution mode when writing to FragDepth
 (#7450)

---
 source/slang/slang-emit-spirv.cpp       | 10 +++++++++-
 tests/spirv/depth-replacing-gt-lt.slang | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/spirv/depth-replacing-gt-lt.slang

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 8e8e7327b..018f833aa 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -4850,7 +4850,15 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
         if (mode == SpvExecutionModeMax)
             return;
 
-        requireSPIRVExecutionMode(nullptr, getIRInstSpvID(entryPoint), mode);
+        // Vulkan spec requires DepthReplacing exec mode when storing to FragDepth,
+        // in addition to DepthLess/DepthGreater modes.
+        requireSPIRVExecutionMode(
+            nullptr,
+            getIRInstSpvID(entryPoint),
+            SpvExecutionModeDepthReplacing);
+
+        if (mode != SpvExecutionModeDepthReplacing)
+            requireSPIRVExecutionMode(nullptr, getIRInstSpvID(entryPoint), mode);
     }
 
     // Make user type name conform to `SPV_GOOGLE_user_type` spec.
diff --git a/tests/spirv/depth-replacing-gt-lt.slang b/tests/spirv/depth-replacing-gt-lt.slang
new file mode 100644
index 000000000..8e0ce6b79
--- /dev/null
+++ b/tests/spirv/depth-replacing-gt-lt.slang
@@ -0,0 +1,16 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+// CHECK: OpExecutionMode {{.*}} DepthReplacing
+// CHECK: OpExecutionMode %FS_WriteDepthGt DepthGreater
+// CHECK: OpExecutionMode %FS_WriteDepthLt DepthLess
+
+[shader("fragment")]
+void FS_WriteDepthGt(out float depth: SV_DepthGreaterEqual)
+{
+    depth = 0.5;
+}
+
+[shader("fragment")]
+void FS_WriteDepthLt(out float depth: SV_DepthLessEqual)
+{
+    depth = 0.5;
+}
-- 
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