[flang-commits] [flang] [flang] Stop tracking memory source after a load in a more explicit manner. (PR #126156)

[Renaud Kauffmann via flang-commits]

https://github.com/Renaud-K updated https://github.com/llvm/llvm-project/pull/126156

>From 7299f21b20cedf0fa902cdc8081039a367d207a2 Mon Sep 17 00:00:00 2001
From: Renaud-K <rkauffmann at nvidia.com>
Date: Thu, 6 Feb 2025 16:10:57 -0800
Subject: [PATCH 1/2] Applying formatting

---
 .../lib/Optimizer/Analysis/AliasAnalysis.cpp  | 47 ++++++++++++++-----
 .../AliasAnalysis/alias-analysis-2.fir        |  6 ++-
 2 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp b/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
index 01f3a0326db216e..ac2de2b6202c37c 100644
--- a/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
+++ b/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
@@ -51,7 +51,7 @@ static bool hasGlobalOpTargetAttr(mlir::Value v, fir::AddrOfOp op) {
       v, fir::GlobalOp::getTargetAttrName(globalOpName));
 }
 
-mlir::Value getOriginalDef(mlir::Value v) {
+static mlir::Value getOriginalDef(mlir::Value v) {
   mlir::Operation *defOp;
   bool breakFromLoop = false;
   while (!breakFromLoop && (defOp = v.getDefiningOp())) {
@@ -578,16 +578,6 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v,
             breakFromLoop = true;
         })
         .Case<fir::LoadOp>([&](auto op) {
-          // If the load is from a leaf source, return the leaf. Do not track
-          // through indirections otherwise.
-          // TODO: Add support to fir.alloca and fir.allocmem
-          auto def = getOriginalDef(op.getMemref());
-          if (isDummyArgument(def) ||
-              def.template getDefiningOp<fir::AddrOfOp>()) {
-            v = def;
-            defOp = v.getDefiningOp();
-            return;
-          }
           // If load is inside target and it points to mapped item,
           // continue tracking.
           Operation *loadMemrefOp = op.getMemref().getDefiningOp();
@@ -600,6 +590,41 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v,
             defOp = v.getDefiningOp();
             return;
           }
+
+          // If we are loading a box reference, but following the data,
+          // we gather the attributes of the box to populate the source
+          // and stop tracking.
+          if (auto boxTy = mlir::dyn_cast<fir::BaseBoxType>(ty);
+              boxTy && followingData) {
+
+            if (mlir::isa<fir::PointerType>(boxTy.getEleTy())) {
+              attributes.set(Attribute::Pointer);
+            }
+
+            auto def = getOriginalDef(op.getMemref());
+            if (auto addrOfOp = def.template getDefiningOp<fir::AddrOfOp>()) {
+              global = addrOfOp.getSymbol();
+
+              if (hasGlobalOpTargetAttr(def, addrOfOp))
+                attributes.set(Attribute::Target);
+
+              type = SourceKind::Global;
+            }
+
+            // TODO: Add support to fir.alloca and fir.allocmem
+            // if (auto allocOp = def.template getDefiningOp<fir::AllocaOp>()) {
+            //   ...
+            // }
+
+            if (isDummyArgument(def)) {
+              defOp = nullptr;
+              v = def;
+            }
+
+            breakFromLoop = true;
+            return;
+          }
+
           // No further tracking for addresses loaded from memory for now.
           type = SourceKind::Indirect;
           breakFromLoop = true;
diff --git a/flang/test/Analysis/AliasAnalysis/alias-analysis-2.fir b/flang/test/Analysis/AliasAnalysis/alias-analysis-2.fir
index ca97c5900281d64..3fbf29ab2eb2926 100644
--- a/flang/test/Analysis/AliasAnalysis/alias-analysis-2.fir
+++ b/flang/test/Analysis/AliasAnalysis/alias-analysis-2.fir
@@ -49,11 +49,13 @@
 
 // TODO: Can the address in a pointer alias the address of a pointer, even when the
 // pointer has no box. Should this be NoAlias?
-// T3: CHECK-DAG: p1.addr#0 <-> p1.tgt#0: MayAlias
+// T3: 
+// CHECK-DAG: p1.addr#0 <-> p1.tgt#0: MayAlias
 
 // The addresses stored in two different pointers can alias, even if one has no
 // box.  In this program, they happen to be the same address.
-// T4: CHECK-DAG: p1.tgt#0 <-> boxp1.addr#0: MayAlias
+// T4: 
+// CHECK-DAG: p1.tgt#0 <-> boxp1.addr#0: MayAlias
 
 func.func @_QFPtest(%arg0: !fir.ref<f32> {fir.bindc_name = "v1", fir.target}, %arg1: !fir.ref<f32> {fir.bindc_name = "v2", fir.target}, %arg2: !fir.ref<!fir.box<!fir.ptr<f32>>> ) attributes {test.ptr = "func"} {
 

>From 8d43bd499923cba34489f55cf72c28ebdfde07f2 Mon Sep 17 00:00:00 2001
From: Renaud-K <rkauffmann at nvidia.com>
Date: Fri, 7 Feb 2025 08:55:39 -0800
Subject: [PATCH 2/2] Removing curly brackets

---
 flang/lib/Optimizer/Analysis/AliasAnalysis.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp b/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
index ac2de2b6202c37c..5827d1c3c529ed2 100644
--- a/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
+++ b/flang/lib/Optimizer/Analysis/AliasAnalysis.cpp
@@ -597,9 +597,8 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v,
           if (auto boxTy = mlir::dyn_cast<fir::BaseBoxType>(ty);
               boxTy && followingData) {
 
-            if (mlir::isa<fir::PointerType>(boxTy.getEleTy())) {
+            if (mlir::isa<fir::PointerType>(boxTy.getEleTy()))
               attributes.set(Attribute::Pointer);
-            }
 
             auto def = getOriginalDef(op.getMemref());
             if (auto addrOfOp = def.template getDefiningOp<fir::AddrOfOp>()) {