[Flang] Turn on alias analysis for locally allocated objects (#143489)

Previously, a bug in the MemCptOpt LLVM IR pass caused issues with
adding alias tags for locally allocated objects for Fortran code.

However, the bug has now been fixed (#129537 ),
and we can safely enable alias tags for these objects. This change should
improve the accuracy of the alias analysis.

More accurate alias analysis assumes that Cray pointers do not alias
with other variables. This assumption is common among other compilers.
If the code violates this assumption, it can lead to incorrect results
(see: #141928)

Author: DominikAdamski

flang/lib/Optimizer/Transforms/AddAliasTags.cpp

@@ -43,13 +43,10 @@ static llvm::cl::opt<bool>
 static llvm::cl::opt<bool>
     enableDirect("direct-tbaa", llvm::cl::init(true), llvm::cl::Hidden,
                  llvm::cl::desc("Add TBAA tags to direct variables"));
-// This is **known unsafe** (misscompare in spec2017/wrf_r). It should
-// not be enabled by default.
-// The code is kept so that these may be tried with new benchmarks to see if
-// this is worth fixing in the future.
-static llvm::cl::opt<bool> enableLocalAllocs(
-    "local-alloc-tbaa", llvm::cl::init(false), llvm::cl::Hidden,
-    llvm::cl::desc("Add TBAA tags to local allocations. UNSAFE."));
+static llvm::cl::opt<bool>
+    enableLocalAllocs("local-alloc-tbaa", llvm::cl::init(true),
+                      llvm::cl::Hidden,
+                      llvm::cl::desc("Add TBAA tags to local allocations."));
 
 namespace {
 

flang/test/Fir/tbaa-codegen2.fir

@@ -100,7 +100,7 @@ module attributes {fir.defaultkind = "a1c4d8i4l4r4", fir.kindmap = "", llvm.targ
 // [...]
 // CHECK:  %[[VAL50:.*]] = getelementptr i32, ptr %{{.*}}, i64 %{{.*}}
 // store to the temporary:
-// CHECK:  store i32 %{{.*}}, ptr %[[VAL50]], align 4, !tbaa ![[DATA_ACCESS_TAG:.*]]
+// CHECK:  store i32 %{{.*}}, ptr %[[VAL50]], align 4, !tbaa ![[TMP_DATA_ACCESS_TAG:.*]]
 // [...]
 
 // CHECK: [[BOX_ACCESS_TAG]] = !{![[BOX_ACCESS_TYPE:.*]], ![[BOX_ACCESS_TYPE]], i64 0}
@@ -111,4 +111,7 @@ module attributes {fir.defaultkind = "a1c4d8i4l4r4", fir.kindmap = "", llvm.targ
 // CHECK: ![[A_ACCESS_TYPE]] = !{!"dummy arg data/_QFfuncEa", ![[ARG_ACCESS_TYPE:.*]], i64 0}
 // CHECK: ![[ARG_ACCESS_TYPE]] = !{!"dummy arg data", ![[DATA_ACCESS_TYPE:.*]], i64 0}
 // CHECK: ![[DATA_ACCESS_TYPE]] = !{!"any data access", ![[ANY_ACCESS_TYPE]], i64 0}
-// CHECK: ![[DATA_ACCESS_TAG]] = !{![[DATA_ACCESS_TYPE]], ![[DATA_ACCESS_TYPE]], i64 0}
+// CHECK: ![[TMP_DATA_ACCESS_TAG]] = !{![[TMP_DATA_ACCESS_TYPE:.*]], ![[TMP_DATA_ACCESS_TYPE]], i64 0}
+// CHECK: ![[TMP_DATA_ACCESS_TYPE]] = !{!"allocated data/", ![[TMP_ACCESS_TYPE:.*]], i64 0}
+// CHECK: ![[TMP_ACCESS_TYPE]] = !{!"allocated data", ![[TARGET_ACCESS_TAG:.*]], i64 0}
+// CHECK: ![[TARGET_ACCESS_TAG]] = !{!"target data", ![[DATA_ACCESS_TYPE]], i64 0}

flang/test/Transforms/tbaa-with-dummy-scope2.fir

@@ -43,12 +43,15 @@ func.func @_QPtest1() attributes {noinline} {
 // CHECK: #[[$ATTR_0:.+]] = #llvm.tbaa_root<id = "Flang function root _QPtest1">
 // CHECK: #[[$ATTR_1:.+]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[$ATTR_0]], 0>}>
 // CHECK: #[[$ATTR_2:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_1]], 0>}>
+// CHECK: #[[$TARGETDATA:.+]] = #llvm.tbaa_type_desc<id = "target data", members = {<#[[$ATTR_2]], 0>}>
 // CHECK: #[[$ATTR_3:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data", members = {<#[[$ATTR_2]], 0>}>
-// CHECK: #[[TARGETDATA:.+]] = #llvm.tbaa_type_desc<id = "target data", members = {<#[[$ATTR_2]], 0>}>
+// CHECK: #[[$LOCAL_ATTR_0:.+]] = #llvm.tbaa_type_desc<id = "allocated data", members = {<#[[$TARGETDATA]], 0>}>
 // CHECK: #[[$ATTR_5:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data/_QFtest1FinnerEx", members = {<#[[$ATTR_3]], 0>}>
-// CHECK: #[[$ATTR_4:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[TARGETDATA]], 0>}>
+// CHECK: #[[$ATTR_4:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[$TARGETDATA]], 0>}>
 // CHECK: #[[$ATTR_7:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_5]], access_type = #[[$ATTR_5]], offset = 0>
+// CHECK: #[[$LOCAL_ATTR_1:.+]] = #llvm.tbaa_type_desc<id = "allocated data/_QFtest1FinnerEy", members = {<#[[$LOCAL_ATTR_0]], 0>}>
 // CHECK: #[[$ATTR_6:.+]] = #llvm.tbaa_type_desc<id = "global data/_QMmEglob", members = {<#[[$ATTR_4]], 0>}>
+// CHECK: #[[$LOCAL_ATTR_2:.+]] = #llvm.tbaa_tag<base_type = #[[$LOCAL_ATTR_1]], access_type = #[[$LOCAL_ATTR_1]], offset = 0>
 // CHECK: #[[$ATTR_8:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_6]], access_type = #[[$ATTR_6]], offset = 0>
 // CHECK-LABEL:   func.func @_QPtest1() attributes {noinline} {
 // CHECK:           %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest1FinnerEy"}
@@ -57,8 +60,8 @@ func.func @_QPtest1() attributes {noinline} {
 // CHECK:           %[[VAL_5:.*]] = fir.dummy_scope : !fir.dscope
 // CHECK:           %[[VAL_6:.*]] = fir.declare %[[VAL_4]] dummy_scope %[[VAL_5]] {uniq_name = "_QFtest1FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
 // CHECK:           %[[VAL_7:.*]] = fir.declare %[[VAL_2]] {uniq_name = "_QFtest1FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
-// CHECK:           fir.store %{{.*}} to %[[VAL_7]] : !fir.ref<i32>
-// CHECK:           %[[VAL_8:.*]] = fir.load %[[VAL_7]] : !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_7]] {tbaa = [#[[$LOCAL_ATTR_2]]]} : !fir.ref<i32>
+// CHECK:           %[[VAL_8:.*]] = fir.load %[[VAL_7]] {tbaa = [#[[$LOCAL_ATTR_2]]]}  : !fir.ref<i32>
 // CHECK:           fir.store %[[VAL_8]] to %[[VAL_6]] {tbaa = [#[[$ATTR_7]]]} : !fir.ref<i32>
 // CHECK:           fir.store %{{.*}} to %[[VAL_4]] {tbaa = [#[[$ATTR_8]]]} : !fir.ref<i32>
 
@@ -87,12 +90,16 @@ func.func @_QPtest2() attributes {noinline} {
 // CHECK: #[[$ATTR_3:.+]] = #llvm.tbaa_type_desc<id = "any access", members = {<#[[$ATTR_1]], 0>}>
 // CHECK: #[[$ATTR_4:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_2]], 0>}>
 // CHECK: #[[$ATTR_5:.+]] = #llvm.tbaa_type_desc<id = "any data access", members = {<#[[$ATTR_3]], 0>}>
+// CHECK: #[[$TARGETDATA_0:.+]] = #llvm.tbaa_type_desc<id = "target data", members = {<#[[$ATTR_4]], 0>}>
 // CHECK: #[[$ATTR_6:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data", members = {<#[[$ATTR_4]], 0>}>
-// CHECK: #[[TARGETDATA:.+]] = #llvm.tbaa_type_desc<id = "target data", members = {<#[[$ATTR_5]], 0>}>
+// CHECK: #[[$TARGETDATA_1:.+]] = #llvm.tbaa_type_desc<id = "target data", members = {<#[[$ATTR_5]], 0>}>
+// CHECK: #[[$LOCAL_ATTR_0:.+]] = #llvm.tbaa_type_desc<id = "allocated data", members = {<#[[$TARGETDATA_0]], 0>}>
 // CHECK: #[[$ATTR_8:.+]] = #llvm.tbaa_type_desc<id = "dummy arg data/_QFtest2FinnerEx", members = {<#[[$ATTR_6]], 0>}>
-// CHECK: #[[$ATTR_7:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[TARGETDATA]], 0>}>
+// CHECK: #[[$ATTR_7:.+]] = #llvm.tbaa_type_desc<id = "global data", members = {<#[[$TARGETDATA_1]], 0>}>
 // CHECK: #[[$ATTR_10:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_8]], access_type = #[[$ATTR_8]], offset = 0>
+// CHECK: #[[$LOCAL_ATTR_1:.+]] = #llvm.tbaa_type_desc<id = "allocated data/_QFtest2FinnerEy", members = {<#[[$LOCAL_ATTR_0]], 0>}>
 // CHECK: #[[$ATTR_9:.+]] = #llvm.tbaa_type_desc<id = "global data/_QMmEglob", members = {<#[[$ATTR_7]], 0>}>
+// CHECK: #[[$LOCAL_ATTR_2:.+]] = #llvm.tbaa_tag<base_type = #[[$LOCAL_ATTR_1]], access_type = #[[$LOCAL_ATTR_1]], offset = 0>
 // CHECK: #[[$ATTR_11:.+]] = #llvm.tbaa_tag<base_type = #[[$ATTR_9]], access_type = #[[$ATTR_9]], offset = 0>
 // CHECK-LABEL:   func.func @_QPtest2() attributes {noinline} {
 // CHECK:           %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFtest2FinnerEy"}
@@ -102,7 +109,7 @@ func.func @_QPtest2() attributes {noinline} {
 // CHECK:           %[[VAL_6:.*]] = fir.dummy_scope : !fir.dscope
 // CHECK:           %[[VAL_7:.*]] = fir.declare %[[VAL_5]] dummy_scope %[[VAL_6]] {uniq_name = "_QFtest2FinnerEx"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
 // CHECK:           %[[VAL_8:.*]] = fir.declare %[[VAL_2]] {uniq_name = "_QFtest2FinnerEy"} : (!fir.ref<i32>) -> !fir.ref<i32>
-// CHECK:           fir.store %{{.*}} to %[[VAL_8]] : !fir.ref<i32>
-// CHECK:           %[[VAL_9:.*]] = fir.load %[[VAL_8]] : !fir.ref<i32>
+// CHECK:           fir.store %{{.*}} to %[[VAL_8]] {tbaa = [#[[$LOCAL_ATTR_2]]]}  : !fir.ref<i32>
+// CHECK:           %[[VAL_9:.*]] = fir.load %[[VAL_8]] {tbaa = [#[[$LOCAL_ATTR_2]]]} : !fir.ref<i32>
 // CHECK:           fir.store %[[VAL_9]] to %[[VAL_7]] {tbaa = [#[[$ATTR_10]]]} : !fir.ref<i32>
 // CHECK:           fir.store %{{.*}} to %[[VAL_5]] {tbaa = [#[[$ATTR_11]]]} : !fir.ref<i32>