[OpenACC][CIR] Implement 'alloca copying' for private lowering (llvm#161382)

The previous patch ensured that we correctly got the allocas put in
place. This patch takes the address of each element of each alloca, and
copies it to the previous one. This allows us to re-form the
pointer-structure for a recipe.

Author: erichkeane

clang/lib/CIR/CodeGen/CIRGenOpenACCRecipe.cpp

@@ -36,6 +36,75 @@ mlir::Block *OpenACCRecipeBuilderBase::createRecipeBlock(mlir::Region &region,
   llvm::SmallVector<mlir::Location> locs{types.size(), loc};
   return builder.createBlock(&region, region.end(), types, locs);
 }
+void OpenACCRecipeBuilderBase::makeAllocaCopy(mlir::Location loc,
+                                              mlir::Type copyType,
+                                              mlir::Value numEltsToCopy,
+                                              mlir::Value offsetPerSubarray,
+                                              mlir::Value destAlloca,
+                                              mlir::Value srcAlloca) {
+  mlir::OpBuilder::InsertionGuard guardCase(builder);
+
+  mlir::Type itrTy = cgf.cgm.convertType(cgf.getContext().UnsignedLongLongTy);
+  auto itrPtrTy = cir::PointerType::get(itrTy);
+  mlir::IntegerAttr itrAlign =
+      cgf.cgm.getSize(cgf.getContext().getTypeAlignInChars(
+          cgf.getContext().UnsignedLongLongTy));
+
+  auto loopBuilder = [&]() {
+    auto itr =
+        cir::AllocaOp::create(builder, loc, itrPtrTy, itrTy, "itr", itrAlign);
+    cir::ConstantOp constZero = builder.getConstInt(loc, itrTy, 0);
+    builder.CIRBaseBuilderTy::createStore(loc, constZero, itr);
+    builder.createFor(
+        loc,
+        /*condBuilder=*/
+        [&](mlir::OpBuilder &b, mlir::Location loc) {
+          // itr < numEltsToCopy
+          // Enforce a trip count of 1 if there wasn't any element count, this
+          // way we can just use this loop with a constant bounds instead of a
+          // separate code path.
+          if (!numEltsToCopy)
+            numEltsToCopy = builder.getConstInt(loc, itrTy, 1);
+
+          auto loadCur = cir::LoadOp::create(builder, loc, {itr});
+          auto cmp = builder.createCompare(loc, cir::CmpOpKind::lt, loadCur,
+                                           numEltsToCopy);
+          builder.createCondition(cmp);
+        },
+        /*bodyBuilder=*/
+        [&](mlir::OpBuilder &b, mlir::Location loc) {
+          // destAlloca[itr] = srcAlloca[offsetPerSubArray * itr];
+          auto loadCur = cir::LoadOp::create(builder, loc, {itr});
+          auto srcOffset = builder.createMul(loc, offsetPerSubarray, loadCur);
+
+          auto ptrToOffsetIntoSrc = cir::PtrStrideOp::create(
+              builder, loc, copyType, srcAlloca, srcOffset);
+
+          auto offsetIntoDecayDest = cir::PtrStrideOp::create(
+              builder, loc, builder.getPointerTo(copyType), destAlloca,
+              loadCur);
+
+          builder.CIRBaseBuilderTy::createStore(loc, ptrToOffsetIntoSrc,
+                                                offsetIntoDecayDest);
+          builder.createYield(loc);
+        },
+        /*stepBuilder=*/
+        [&](mlir::OpBuilder &b, mlir::Location loc) {
+          // Simple increment of the iterator.
+          auto load = cir::LoadOp::create(builder, loc, {itr});
+          auto inc = cir::UnaryOp::create(builder, loc, load.getType(),
+                                          cir::UnaryOpKind::Inc, load);
+          builder.CIRBaseBuilderTy::createStore(loc, inc, itr);
+          builder.createYield(loc);
+        });
+  };
+
+  cir::ScopeOp::create(builder, loc,
+                       [&](mlir::OpBuilder &b, mlir::Location loc) {
+                         loopBuilder();
+                         builder.createYield(loc);
+                       });
+}
 
 mlir::Value OpenACCRecipeBuilderBase::makeBoundsAlloca(
     mlir::Block *block, SourceRange exprRange, mlir::Location loc,
@@ -78,6 +147,10 @@ mlir::Value OpenACCRecipeBuilderBase::makeBoundsAlloca(
 
   bool lastBoundWasArray = isArrayTy(boundTypes.back());
 
+  // Make sure we track a moving version of this so we can get our
+  // 'copying' back to correct.
+  mlir::Value lastAlloca = initialAlloca;
+
   // Since we're iterating the types in reverse, this sets up for each index
   // corresponding to the boundsRange to be the 'after application of the
   // bounds.
@@ -125,14 +198,21 @@ mlir::Value OpenACCRecipeBuilderBase::makeBoundsAlloca(
 
       mlir::Type eltTy = cgf.convertType(resultType);
       cir::PointerType ptrTy = builder.getPointerTo(eltTy);
-      builder.createAlloca(loc, ptrTy, eltTy, "openacc.init.bounds",
-                           cgf.getContext().getTypeAlignInChars(resultType),
-                           curSize);
-
-      // TODO: OpenACC : At this point we should be copying the addresses of
-      // each element of this to the last allocation.  At the moment, that is
-      // not yet implemented.
-      cgf.cgm.errorNYI(exprRange, "OpenACC recipe alloca copying");
+      mlir::Value curAlloca = builder.createAlloca(
+          loc, ptrTy, eltTy, "openacc.init.bounds",
+          cgf.getContext().getTypeAlignInChars(resultType), curSize);
+
+      makeAllocaCopy(loc, ptrTy, cumulativeElts, eltsPerSubArray, lastAlloca,
+                     curAlloca);
+      lastAlloca = curAlloca;
+    } else {
+      // In the case of an array, we just need to decay the pointer, so just do
+      // a zero-offset stride on the last alloca to decay it down an array
+      // level.
+      cir::ConstantOp constZero = builder.getConstInt(loc, itrTy, 0);
+      lastAlloca = builder.getArrayElement(loc, loc, lastAlloca,
+                                           cgf.convertType(resultType),
+                                           constZero, /*shouldDecay=*/true);
     }
 
     cumulativeElts = eltsToAlloca;

clang/lib/CIR/CodeGen/CIRGenOpenACCRecipe.h

@@ -24,6 +24,10 @@
 
 namespace clang::CIRGen {
 class OpenACCRecipeBuilderBase {
+  // makes the copy of the addresses of an alloca to the previous allocation.
+  void makeAllocaCopy(mlir::Location loc, mlir::Type copyType,
+                      mlir::Value numEltsToCopy, mlir::Value offsetPerSubarray,
+                      mlir::Value destAlloca, mlir::Value srcAlloca);
   // This function generates the required alloca, similar to
   // 'emitAutoVarAlloca', except for the OpenACC array/pointer types.
   mlir::Value makeBoundsAlloca(mlir::Block *block, SourceRange exprRange,