[Mlir-commits] [mlir] [MLIR][LLVMIR] Preserve byval alignment in memcpy after inlining (PR #185433)

[llvmlistbot at llvm.org]

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir-llvm

Author: Berke Ates (Berke-Ates)

<details>
<summary>Changes</summary>

This PR adds alignment attributes to the generated memcpy intrinsics after inlining functions with byval arguments.

---
Full diff: https://github.com/llvm/llvm-project/pull/185433.diff


2 Files Affected:

- (modified) mlir/lib/Dialect/LLVMIR/Transforms/InlinerInterfaceImpl.cpp (+12-1) 
- (modified) mlir/test/Dialect/LLVMIR/inlining.mlir (+20) 


``````````diff
diff --git a/mlir/lib/Dialect/LLVMIR/Transforms/InlinerInterfaceImpl.cpp b/mlir/lib/Dialect/LLVMIR/Transforms/InlinerInterfaceImpl.cpp
index b61138ad4678b..c9b6359ecc433 100644
--- a/mlir/lib/Dialect/LLVMIR/Transforms/InlinerInterfaceImpl.cpp
+++ b/mlir/lib/Dialect/LLVMIR/Transforms/InlinerInterfaceImpl.cpp
@@ -623,8 +623,19 @@ static Value handleByValArgumentInit(OpBuilder &builder, Location loc,
   Value copySize =
       LLVM::ConstantOp::create(builder, loc, builder.getI64Type(),
                                builder.getI64IntegerAttr(elementTypeSize));
+  // Preserve the alignment of the destination (alloca) in the memcpy's
+  // arg_attrs.
+  MLIRContext *ctx = builder.getContext();
+  NamedAttribute dstAlignAttr =
+      builder.getNamedAttr(LLVM::LLVMDialect::getAlignAttrName(),
+                           builder.getI64IntegerAttr(targetAlignment));
+  ArrayAttr argAttrs =
+      builder.getArrayAttr({DictionaryAttr::get(ctx, {dstAlignAttr})});
   LLVM::MemcpyOp::create(builder, loc, allocaOp, argument, copySize,
-                         /*isVolatile=*/false);
+                         /*isVolatile=*/false,
+                         /*access_groups=*/nullptr, /*alias_scopes=*/nullptr,
+                         /*noalias_scopes=*/nullptr, /*tbaa=*/nullptr, argAttrs,
+                         /*res_attrs=*/nullptr);
   return allocaOp;
 }
 
diff --git a/mlir/test/Dialect/LLVMIR/inlining.mlir b/mlir/test/Dialect/LLVMIR/inlining.mlir
index cc3600af431ea..e2c60da47e180 100644
--- a/mlir/test/Dialect/LLVMIR/inlining.mlir
+++ b/mlir/test/Dialect/LLVMIR/inlining.mlir
@@ -570,6 +570,26 @@ llvm.func @test_byval_global() {
 
 // -----
 
+// Check that alignment information is preserved in the memcpy when inlining
+// byval arguments.
+
+llvm.func @byval_aligned_arg(%ptr : !llvm.ptr { llvm.byval = i32, llvm.align = 16 }) {
+  llvm.return
+}
+
+// CHECK-LABEL: llvm.func @test_byval_memcpy_alignment
+// CHECK-SAME: %[[PTR:[a-zA-Z0-9_]+]]: !llvm.ptr
+llvm.func @test_byval_memcpy_alignment(%ptr : !llvm.ptr) {
+  // Verify the memcpy carries the alignment info from the byval attribute.
+  // CHECK: %[[ALLOCA:.+]] = llvm.alloca{{.+}}alignment = 16
+  // CHECK: "llvm.intr.memcpy"(%[[ALLOCA]], %[[PTR]]
+  // CHECK-SAME: {llvm.align = 16 : i64}
+  llvm.call @byval_aligned_arg(%ptr) : (!llvm.ptr) -> ()
+  llvm.return
+}
+
+// -----
+
 // Check that inlining does not hoist byval allocas out of automatic allocation
 // scopes, such as parallel forall regions. Each parallel iteration must have
 // its own private copy of the byval argument.

``````````

</details>


https://github.com/llvm/llvm-project/pull/185433