swr/rast: Fix alloca usage in jitter

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.

Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>

3 files changed, 20 insertions, 0 deletions

diff --git a/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp b/src/gallium/drivers/swr/rasterizer/jitter/builder.cpp
index 53947c317e..bd815606fb 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 4c79bab964..27a32bc3e3 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 c5f0b2b9fe..eccf0ad0d6 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));