From 964fcdc2ad8a5e646ce9f1dd6b0e462ca9f7d772 Mon Sep 17 00:00:00 2001
From: Rye <rye@alchemyviewer.org>
Date: Wed, 15 Oct 2025 18:30:36 -0400
Subject: Introduce support for GL_ATI_meminfo for getting gpu memory on linux

Signed-off-by: Rye <rye@alchemyviewer.org>
---
 indra/llrender/llgl.cpp | 40 +++++++++++++++++++++++++++++++---------
 indra/llrender/llgl.h   |  1 +
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/indra/llrender/llgl.cpp b/indra/llrender/llgl.cpp
index d13b98e274..6c0fcb8960 100644
--- a/indra/llrender/llgl.cpp
+++ b/indra/llrender/llgl.cpp
@@ -1042,7 +1042,6 @@ void LLGLManager::initWGL()
         GLH_EXT_NAME(wglGetGPUIDsAMD) = (PFNWGLGETGPUIDSAMDPROC)GLH_EXT_GET_PROC_ADDRESS("wglGetGPUIDsAMD");
         GLH_EXT_NAME(wglGetGPUInfoAMD) = (PFNWGLGETGPUINFOAMDPROC)GLH_EXT_GET_PROC_ADDRESS("wglGetGPUInfoAMD");
     }
-    mHasNVXGpuMemoryInfo = ExtensionExists("GL_NVX_gpu_memory_info", gGLHExts.mSysExts);
 
     if (ExtensionExists("WGL_EXT_swap_control", gGLHExts.mSysExts))
     {
@@ -1203,16 +1202,29 @@ bool LLGLManager::initGL()
         {
             LL_WARNS("RenderInit") << "VRAM Detected (AMDAssociations):" << mVRAM << LL_ENDL;
         }
-    }
-    else if (mHasNVXGpuMemoryInfo)
+    } else
+#endif
+#if LL_WINDOWS || LL_LINUX
     {
-        GLint mem_kb = 0;
-        glGetIntegerv(GL_GPU_MEMORY_INFO_DEDICATED_VIDMEM_NVX, &mem_kb);
-        mVRAM = mem_kb / 1024;
-
-        if (mVRAM != 0)
+        if (mHasNVXGpuMemoryInfo && mVRAM == 0)
         {
-            LL_WARNS("RenderInit") << "VRAM Detected (NVXGpuMemoryInfo):" << mVRAM << LL_ENDL;
+            GLint mem_kb = 0;
+            glGetIntegerv(GL_GPU_MEMORY_INFO_DEDICATED_VIDMEM_NVX, &mem_kb);
+            mVRAM = mem_kb / 1024;
+
+            if (mVRAM != 0)
+            {
+                LL_WARNS("RenderInit") << "VRAM Detected (NVXGpuMemoryInfo):" << mVRAM << LL_ENDL;
+            }
+        }
+
+        if (mHasATIMemInfo && mVRAM == 0)
+        { //ask the gl how much vram is free at startup and attempt to use no more than half of that
+            S32 meminfo[4];
+            glGetIntegerv(GL_TEXTURE_FREE_MEMORY_ATI, meminfo);
+
+            mVRAM = meminfo[0] / 1024;
+            LL_INFOS("RenderInit") << "VRAM Detected (ATIMemInfo):" << mVRAM << LL_ENDL;
         }
     }
 #endif
@@ -1406,6 +1418,16 @@ void LLGLManager::initExtensions()
         mHasAnisotropic = ExtensionExists("GL_EXT_texture_filter_anisotropic", gGLHExts.mSysExts);
     }
 
+#if LL_WINDOWS || LL_LINUX
+    if( gGLHExts.mSysExts )
+    {
+        mHasNVXGpuMemoryInfo = ExtensionExists("GL_NVX_gpu_memory_info", gGLHExts.mSysExts);
+        mHasATIMemInfo = ExtensionExists("GL_ATI_meminfo", gGLHExts.mSysExts);
+    }
+    else
+        LL_WARNS() << "gGLHExts.mSysExts is not set.?" << LL_ENDL;
+#endif
+
     // Misc
     glGetIntegerv(GL_MAX_ELEMENTS_VERTICES, (GLint*) &mGLMaxVertexRange);
     glGetIntegerv(GL_MAX_ELEMENTS_INDICES, (GLint*) &mGLMaxIndexRange);
diff --git a/indra/llrender/llgl.h b/indra/llrender/llgl.h
index 24ba4d6deb..8a00e513ae 100644
--- a/indra/llrender/llgl.h
+++ b/indra/llrender/llgl.h
@@ -99,6 +99,7 @@ public:
     // Vendor-specific extensions
     bool mHasAMDAssociations = false;
     bool mHasNVXGpuMemoryInfo = false;
+    bool mHasATIMemInfo = false;
 
     bool mIsAMD;
     bool mIsNVIDIA;
-- 
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