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[flang][debug] Don't generate debug for compiler-generated variables #112423

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merged 4 commits into from
Oct 21, 2024
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[flang][debug] Don't generate debug for compiler-generated variables #112423

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[flang][debug] Don't generate debug info for compiler-generated varia…
abidh Oct 15, 2024
3217ca6
Correct a problem in the test.
abidh Oct 15, 2024
3122f82
Add a comment.
abidh Oct 15, 2024
f22f41e
Handle review comments.
abidh Oct 16, 2024
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11 changes: 7 additions & 4 deletions flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -211,10 +211,13 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
if (result.first != fir::NameUniquer::NameKind::VARIABLE)
return;

// Discard entries that describe a derived type. Usually start with '.c.',
// '.dt.' or '.n.'. It would be better if result of the deconstruct had a flag
// for such values so that we dont have to look at string values.
if (!result.second.name.empty() && result.second.name[0] == '.')
// Discard entries that describe a derived type. They start with either '.' or
// 'X'. We filter both of them out. Note that NameUniquer makes the name lower
// case so user variables should be safe. It would be better if result of the
// deconstruct had a flag for such values so that we dont have to look at
// string values.
if (!result.second.name.empty() &&
(result.second.name[0] == '.' || result.second.name[0] == 'X'))
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@jeanPerier jeanPerier Oct 16, 2024

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Please move the result.second.name[0] == '.' || result.second.name[0] == 'X' part into some static fir::NameUniquer::isSpecialSymbol(llvm::StringRef name) helper in Optimizer/Support/InternalNames so that the usages of these delimiters are better centralized and advertise.

Long term, it may be better to have some compiler generated flag attributes on the global/declare for such variables (and others) rather than relying on the names.
In semantics, these variables are tagged with the CompilerCreated symbol attribute, but it is currently not represented in FIR.

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@abidh abidh Oct 16, 2024

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Thanks for the suggestion. I have moved the code into a separate function.

return;

unsigned line = getLineFromLoc(globalOp.getLoc());
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8 changes: 8 additions & 0 deletions flang/test/Integration/debug-extra-global-2.f90
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@@ -0,0 +1,8 @@
! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck %s

module m
integer XcX
end

! Test that global starting with 'X' don't get filtered.
CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})
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@jeanPerier jeanPerier Oct 16, 2024

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Suggested change
CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})
! CHECK: !DIGlobalVariable(name: "xcx", linkageName: "_QMmExcx"{{.*}})

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@abidh abidh Oct 16, 2024

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Thanks for catching this. Fixed.

14 changes: 14 additions & 0 deletions flang/test/Integration/debug-extra-global.f90
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@@ -0,0 +1,14 @@
! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck %s

program test
type t1
integer :: XcX
integer :: xdtx
end type
type(t1) :: var
var%XcX = 2
var%xdtx = 3
end

! Test that there is no debug info for compiler generated globals.
! CHECK-NOT: DIGlobalVariable
18 changes: 18 additions & 0 deletions flang/test/Transforms/debug-extra-global.fir
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@@ -0,0 +1,18 @@
// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s

module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
fir.global linkonce_odr @_QFEXnXxcx constant target : !fir.char<1,3> {
%0 = fir.string_lit "xcx"(3) : !fir.char<1,3>
fir.has_value %0 : !fir.char<1,3>
} loc(#loc1)
fir.global linkonce_odr @_QFEXnXxdtx constant target : !fir.char<1,4> {
%0 = fir.string_lit "xdtx"(4) : !fir.char<1,4>
fir.has_value %0 : !fir.char<1,4>
} loc(#loc1)
}
#loc1 = loc("derived.f90":24:1)

// Test that no di_global_variable gets created for these compile generated
// globals.

// CHECK-NOT: #di_global_variable
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