[Mesa-dev] [PATCH 32/45] swr/rast: Fix alloca usage in jitter

[George Kyriazis]

Fix issue where temporary allocas were getting hoisted to function entry
unnecessarily. We now explicitly mark temporary allocas and skip hoisting
during the hoist pass. Shuold reduce stack usage.
---
 src/gallium/drivers/swr/rasterizer/jitter/builder.cpp   | 17 +++++++++++++++++
 src/gallium/drivers/swr/rasterizer/jitter/builder.h     |  2 ++
 .../drivers/swr/rasterizer/jitter/builder_mem.cpp       |  1 +
 3 files changed, 20 insertions(+)

diff --git a/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp b/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp
index 53947c3..bd81560 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp
@@ -111,4 +111,21 @@ namespace SwrJit
         mSimdVectorIntTy = ArrayType::get(mSimdInt32Ty, 4);
         mSimdVectorTRTy = ArrayType::get(mSimdFP32Ty, 5);
     }
+
+    /// @brief Mark this alloca as temporary to avoid hoisting later on
+    void Builder::SetTempAlloca(Value* inst)
+    {
+        AllocaInst* pAlloca = dyn_cast<AllocaInst>(inst);
+        SWR_ASSERT(pAlloca, "Unexpected non-alloca instruction");
+        MDNode* N = MDNode::get(JM()->mContext, MDString::get(JM()->mContext, "is_temp_alloca"));
+        pAlloca->setMetadata("is_temp_alloca", N);
+    }
+
+    bool Builder::IsTempAlloca(Value* inst)
+    {
+        AllocaInst* pAlloca = dyn_cast<AllocaInst>(inst);
+        SWR_ASSERT(pAlloca, "Unexpected non-alloca instruction");
+
+        return (pAlloca->getMetadata("is_temp_alloca") != nullptr);
+    }
 }
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/builder.h b/src/gallium/drivers/swr/rasterizer/jitter/builder.h
index 4c79bab..27a32bc 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/builder.h
+++ b/src/gallium/drivers/swr/rasterizer/jitter/builder.h
@@ -96,6 +96,8 @@ namespace SwrJit
         Type*                mSimd32Int8Ty;
 
         void SetTargetWidth(uint32_t width);
+        void SetTempAlloca(Value* inst);
+        bool IsTempAlloca(Value* inst);
 
 #include "gen_builder.hpp"
 #include "gen_builder_meta.hpp"
diff --git a/src/gallium/drivers/swr/rasterizer/jitter/builder_mem.cpp b/src/gallium/drivers/swr/rasterizer/jitter/builder_mem.cpp
index cd9806a..5d8637e 100644
--- a/src/gallium/drivers/swr/rasterizer/jitter/builder_mem.cpp
+++ b/src/gallium/drivers/swr/rasterizer/jitter/builder_mem.cpp
@@ -229,6 +229,7 @@ namespace SwrJit
 
             // store vSrc on the stack.  this way we can select between a valid load address and the vSrc address
             Value* vSrcPtr = ALLOCA(vSrc->getType());
+            SetTempAlloca(vSrcPtr);
             STORE(vSrc, vSrcPtr);
 
             vGather = UndefValue::get(VectorType::get(mDoubleTy, 4));
-- 
2.7.4