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[Flang] Do not attach tbaa tags for local pointers #143376

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[Flang] Do not attach tbaa tags for local pointers #143376

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12 changes: 12 additions & 0 deletions flang/lib/Optimizer/Transforms/AddAliasTags.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,15 @@ static llvm::cl::opt<bool>
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."));
// This is **known unsafe** (miscompare in Fujitsu: Fortran/0614/0614_0005.f
// for ARM). Detailed analysis of the root cause:
// https://github.com/llvm/llvm-project/issues/141928
// The code is kept so that these may be tried with new benchmarks to see if
// this is worth fixing in the future. This flag has no effect unless
// enableLocalAllocs is set
static llvm::cl::opt<bool> enablePtrLocalAllocs(
"ptr-local-alloc-tbaa", llvm::cl::init(false), llvm::cl::Hidden,
llvm::cl::desc("Add TBAA tags to local pointer allocations. UNSAFE."));

namespace {

Expand Down Expand Up @@ -287,6 +296,9 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
<< "WARN: unknown defining op for SourceKind::Allocate " << *op
<< "\n");
} else if (source.isPointer()) {
// Do not add tbaa tags for local pointers unless flag is set
if (!enablePtrLocalAllocs)
return;
LLVM_DEBUG(llvm::dbgs().indent(2)
<< "Found reference to allocation at " << *op << "\n");
tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
Expand Down
4 changes: 3 additions & 1 deletion flang/test/Transforms/tbaa3.fir
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
// RUN: fir-opt --fir-add-alias-tags %s | FileCheck --check-prefixes=ALL,DEFAULT %s
// RUN: fir-opt --fir-add-alias-tags --local-alloc-tbaa %s | FileCheck --check-prefixes=ALL,LOCAL %s
// RUN: fir-opt --fir-add-alias-tags --local-alloc-tbaa --ptr-local-alloc-tbaa %s | FileCheck --check-prefixes=ALL,PTR-LOCAL %s

// Test AddAliasTagsPass creating sub-tree for TARGET/POINTER variables.

Expand Down Expand Up @@ -298,7 +299,8 @@ module {
%83 = fir.array_coor %80(%82) %c1 : (!fir.box<!fir.ptr<!fir.array<?xf32>>>, !fir.shift<1>, index) -> !fir.ref<f32>
// real, pointer :: localp(:)
// DEFAULT-NOT: fir.store{{.*}}tbaa
// LOCAL: fir.store{{.*}}{tbaa = [#[[TARGETTAG]]]} : !fir.ref<f32>
// LOCAL-NOT: fir.store{{.*}}{tbaa = [#[[TARGETTAG]]]} : !fir.ref<f32>
// PTR-LOCAL: fir.store{{.*}}{tbaa = [#[[TARGETTAG]]]} : !fir.ref<f32>
fir.store %cst to %83 : !fir.ref<f32>
// ALL-NOT: fir.load{{.*}}tbaa
%84 = fir.load %27 : !fir.ref<!fir.box<!fir.heap<!fir.array<?xf32>>>>
Expand Down
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