[Mlir-commits] [mlir] 4df44c4 - [mlir] Only treat "Alloc" effects as dead if they are for operation results.

[River Riddle]

Author: River Riddle
Date: 2020-03-14T13:53:56-07:00
New Revision: 4df44c4f9c0f07109eadcf0032a817da2f37151e

URL: https://github.com/llvm/llvm-project/commit/4df44c4f9c0f07109eadcf0032a817da2f37151e
DIFF: https://github.com/llvm/llvm-project/commit/4df44c4f9c0f07109eadcf0032a817da2f37151e.diff

LOG: [mlir] Only treat "Alloc" effects as dead if they are for operation results.

Allocate could be used for an "output" of an operation in the case of buffer-style operations.

Added: 
    

Modified: 
    mlir/lib/Interfaces/SideEffects.cpp

Removed: 
    


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diff  --git a/mlir/lib/Interfaces/SideEffects.cpp b/mlir/lib/Interfaces/SideEffects.cpp
index 53406c6e8b32..aa670d591a0a 100644
--- a/mlir/lib/Interfaces/SideEffects.cpp
+++ b/mlir/lib/Interfaces/SideEffects.cpp
@@ -63,9 +63,13 @@ static bool wouldOpBeTriviallyDeadImpl(Operation *rootOp) {
       // memory.
       SmallVector<MemoryEffects::EffectInstance, 1> effects;
       effectInterface.getEffects(effects);
-      if (!llvm::all_of(effects, [](const auto &it) {
-            return isa<MemoryEffects::Read>(it.getEffect()) ||
-                   isa<MemoryEffects::Allocate>(it.getEffect());
+      if (!llvm::all_of(effects, [op](const MemoryEffects::EffectInstance &it) {
+            // We can drop allocations if the value is a result of the
+            // operation.
+            if (isa<MemoryEffects::Allocate>(it.getEffect()))
+              return it.getValue() && it.getValue().getDefiningOp() == op;
+            // Otherwise, the effect must be a read.
+            return isa<MemoryEffects::Read>(it.getEffect());
           })) {
         return false;
       }