[llvm] Use DIExpression::foldConstantMath() at the result of an appendOpsToArg() (PR #71721)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 8 10:41:05 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-ir
@llvm/pr-subscribers-debuginfo
Author: Shubham Sandeep Rastogi (rastogishubham)
<details>
<summary>Changes</summary>
This patch uses `DIExpression::foldConstantMath()` at the end of a `DIExpression::appendOpsToArg()`. Which should help in reducing the size of DIExpressions that grow because of salvaging debug info
After checking the size of the debug_loc section with and without this change, I saw a decrease of about 300KB, where the debug_loc section is about 211 MB in size
This is part of a stack of patches and comes after:
https://github.com/llvm/llvm-project/pull/69768
https://github.com/llvm/llvm-project/pull/71717
https://github.com/llvm/llvm-project/pull/71718
https://github.com/llvm/llvm-project/pull/71719
---
Patch is 32.09 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/71721.diff
6 Files Affected:
- (modified) llvm/include/llvm/IR/DebugInfoMetadata.h (+85)
- (modified) llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h (-61)
- (modified) llvm/lib/IR/DebugInfoMetadata.cpp (+284-3)
- (modified) llvm/test/Bitcode/upgrade-dbg-addr.ll (+1-1)
- (modified) llvm/test/DebugInfo/MIR/AArch64/dbgcall-site-expr-chain.mir (+2-2)
- (modified) llvm/unittests/IR/MetadataTest.cpp (+382)
``````````diff
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index b347664883fd9f2..354ae48c3d676c1 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -3044,6 +3044,11 @@ class DIExpression : public MDNode {
/// expression and constant on failure.
std::pair<DIExpression *, const ConstantInt *>
constantFold(const ConstantInt *CI);
+
+ /// Try to shorten an expression with constand math operations that can be
+ /// evaulated at compile time. Returns a new expression on success, or the old
+ /// expression if there is nothing to be reduced.
+ DIExpression *foldConstantMath();
};
inline bool operator==(const DIExpression::FragmentInfo &A,
@@ -3073,6 +3078,86 @@ template <> struct DenseMapInfo<DIExpression::FragmentInfo> {
static bool isEqual(const FragInfo &A, const FragInfo &B) { return A == B; }
};
+/// Holds a DIExpression and keeps track of how many operands have been consumed
+/// so far.
+class DIExpressionCursor {
+ DIExpression::expr_op_iterator Start, End;
+
+public:
+ DIExpressionCursor(const DIExpression *Expr) {
+ if (!Expr) {
+ assert(Start == End);
+ return;
+ }
+ Start = Expr->expr_op_begin();
+ End = Expr->expr_op_end();
+ }
+
+ DIExpressionCursor(ArrayRef<uint64_t> Expr)
+ : Start(Expr.begin()), End(Expr.end()) {}
+
+ DIExpressionCursor(const DIExpressionCursor &) = default;
+
+ /// Consume one operation.
+ std::optional<DIExpression::ExprOperand> take() {
+ if (Start == End)
+ return std::nullopt;
+ return *(Start++);
+ }
+
+ /// Consume N operations.
+ void consume(unsigned N) { std::advance(Start, N); }
+
+ /// Return the current operation.
+ std::optional<DIExpression::ExprOperand> peek() const {
+ if (Start == End)
+ return std::nullopt;
+ return *(Start);
+ }
+
+ /// Return the next operation.
+ std::optional<DIExpression::ExprOperand> peekNext() const {
+ if (Start == End)
+ return std::nullopt;
+
+ auto Next = Start.getNext();
+ if (Next == End)
+ return std::nullopt;
+
+ return *Next;
+ }
+
+ std::optional<DIExpression::ExprOperand> peekNextN(unsigned N) const {
+ if (Start == End)
+ return std::nullopt;
+ DIExpression::expr_op_iterator Nth = Start;
+ for (unsigned I = 0; I < N; I++) {
+ Nth = Nth.getNext();
+ if (Nth == End)
+ return std::nullopt;
+ }
+ return *Nth;
+ }
+
+ void assignNewExpr(ArrayRef<uint64_t> Expr) {
+ DIExpression::expr_op_iterator NewStart(Expr.begin());
+ DIExpression::expr_op_iterator NewEnd(Expr.end());
+ this->Start = NewStart;
+ this->End = NewEnd;
+ }
+
+ /// Determine whether there are any operations left in this expression.
+ operator bool() const { return Start != End; }
+
+ DIExpression::expr_op_iterator begin() const { return Start; }
+ DIExpression::expr_op_iterator end() const { return End; }
+
+ /// Retrieve the fragment information, if any.
+ std::optional<DIExpression::FragmentInfo> getFragmentInfo() const {
+ return DIExpression::getFragmentInfo(Start, End);
+ }
+};
+
/// Global variables.
///
/// TODO: Remove DisplayName. It's always equal to Name.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 667a9efc6f6c04f..4daa78b15b8e298 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -31,67 +31,6 @@ class DIELoc;
class TargetRegisterInfo;
class MachineLocation;
-/// Holds a DIExpression and keeps track of how many operands have been consumed
-/// so far.
-class DIExpressionCursor {
- DIExpression::expr_op_iterator Start, End;
-
-public:
- DIExpressionCursor(const DIExpression *Expr) {
- if (!Expr) {
- assert(Start == End);
- return;
- }
- Start = Expr->expr_op_begin();
- End = Expr->expr_op_end();
- }
-
- DIExpressionCursor(ArrayRef<uint64_t> Expr)
- : Start(Expr.begin()), End(Expr.end()) {}
-
- DIExpressionCursor(const DIExpressionCursor &) = default;
-
- /// Consume one operation.
- std::optional<DIExpression::ExprOperand> take() {
- if (Start == End)
- return std::nullopt;
- return *(Start++);
- }
-
- /// Consume N operations.
- void consume(unsigned N) { std::advance(Start, N); }
-
- /// Return the current operation.
- std::optional<DIExpression::ExprOperand> peek() const {
- if (Start == End)
- return std::nullopt;
- return *(Start);
- }
-
- /// Return the next operation.
- std::optional<DIExpression::ExprOperand> peekNext() const {
- if (Start == End)
- return std::nullopt;
-
- auto Next = Start.getNext();
- if (Next == End)
- return std::nullopt;
-
- return *Next;
- }
-
- /// Determine whether there are any operations left in this expression.
- operator bool() const { return Start != End; }
-
- DIExpression::expr_op_iterator begin() const { return Start; }
- DIExpression::expr_op_iterator end() const { return End; }
-
- /// Retrieve the fragment information, if any.
- std::optional<DIExpression::FragmentInfo> getFragmentInfo() const {
- return DIExpression::getFragmentInfo(Start, End);
- }
-};
-
/// Base class containing the logic for constructing DWARF expressions
/// independently of whether they are emitted into a DIE or into a .debug_loc
/// entry.
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index f7f36129ec8557c..4e4b243a1f0a50a 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -1782,7 +1782,7 @@ DIExpression *DIExpression::appendOpsToArg(const DIExpression *Expr,
if (StackValue)
NewOps.push_back(dwarf::DW_OP_stack_value);
- return DIExpression::get(Expr->getContext(), NewOps);
+ return DIExpression::get(Expr->getContext(), NewOps)->foldConstantMath();
}
DIExpression *DIExpression::replaceArg(const DIExpression *Expr,
@@ -1857,11 +1857,10 @@ DIExpression *DIExpression::append(const DIExpression *Expr,
}
Op.appendToVector(NewOps);
}
-
NewOps.append(Ops.begin(), Ops.end());
auto *result = DIExpression::get(Expr->getContext(), NewOps);
assert(result->isValid() && "concatenated expression is not valid");
- return result;
+ return result->foldConstantMath();
}
DIExpression *DIExpression::appendToStack(const DIExpression *Expr,
@@ -1998,6 +1997,288 @@ DIExpression::constantFold(const ConstantInt *CI) {
ConstantInt::get(getContext(), NewInt)};
}
+static bool isConstOperation(uint64_t Op) {
+ return Op == dwarf::DW_OP_constu || Op == dwarf::DW_OP_consts;
+}
+
+static bool operationIsNoOp(uint64_t Op, uint64_t Val) {
+ switch (Op) {
+ case dwarf::DW_OP_plus:
+ case dwarf::DW_OP_minus:
+ case dwarf::DW_OP_shl:
+ case dwarf::DW_OP_shr:
+ return Val == 0;
+ case dwarf::DW_OP_mul:
+ case dwarf::DW_OP_div:
+ return Val == 1;
+ default:
+ return false;
+ }
+}
+
+static std::optional<uint64_t>
+foldOperationIfPossible(uint64_t Op, uint64_t Operand1, uint64_t Operand2) {
+ switch (Op) {
+ case dwarf::DW_OP_plus:
+ return Operand1 + Operand2;
+ case dwarf::DW_OP_minus:
+ return Operand1 - Operand2;
+ case dwarf::DW_OP_shl:
+ return Operand1 << Operand2;
+ case dwarf::DW_OP_shr:
+ return Operand1 >> Operand2;
+ case dwarf::DW_OP_mul:
+ return Operand1 * Operand2;
+ case dwarf::DW_OP_div:
+ return Operand1 / Operand2;
+ default:
+ return std::nullopt;
+ }
+}
+
+static bool operationsAreFoldableAndCommutative(uint64_t Op1, uint64_t Op2) {
+ if (Op1 != Op2)
+ return false;
+ switch (Op1) {
+ case dwarf::DW_OP_plus:
+ case dwarf::DW_OP_mul:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static void moveCursorAndLocPos(DIExpressionCursor &Cursor, uint64_t &Loc,
+ const DIExpression::ExprOperand &Op) {
+ Cursor.consume(1);
+ Loc = Loc + Op.getSize();
+}
+
+DIExpression *DIExpression::foldConstantMath() {
+
+ SmallVector<uint64_t, 8> WorkingOps;
+ WorkingOps.append(Elements.begin(), Elements.end());
+ uint64_t Loc = 0;
+ DIExpressionCursor Cursor(WorkingOps);
+
+ while (Loc < WorkingOps.size()) {
+
+ auto Op1 = Cursor.peek();
+ // Expression has no operations, exit
+ if (!Op1)
+ break;
+ auto Op1Raw = Op1->getOp();
+ auto Op1Arg = Op1->getArg(0);
+
+ // {DW_OP_plus_uconst, 0} -> {}
+ if (Op1Raw == dwarf::DW_OP_plus_uconst && Op1Arg == 0) {
+ WorkingOps.erase(WorkingOps.begin() + Loc, WorkingOps.begin() + Loc + 2);
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+
+ if (!isConstOperation(Op1Raw) && Op1Raw != dwarf::DW_OP_plus_uconst) {
+ // Early exit, all of the following patterns start with a constant value
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+
+ auto Op2 = Cursor.peekNext();
+ // All following patterns require at least 2 Operations, exit
+ if (!Op2)
+ break;
+ auto Op2Raw = Op2->getOp();
+
+ // {DW_OP_const[u, s], 0, DW_OP_[plus, minus, shl, shr]} -> {}
+ // {DW_OP_const[u, s], 1, DW_OP_[mul, div]} -> {}
+ if (isConstOperation(Op1Raw) && operationIsNoOp(Op2Raw, Op1Arg)) {
+ WorkingOps.erase(WorkingOps.begin() + Loc, WorkingOps.begin() + Loc + 3);
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op2Arg = Op2->getArg(0);
+
+ // {DW_OP_plus_uconst, Const1, DW_OP_plus_uconst, Const2} ->
+ // {DW_OP_plus_uconst, Const1 + Const2}
+ if (Op1Raw == dwarf::DW_OP_plus_uconst &&
+ Op2Raw == dwarf::DW_OP_plus_uconst) {
+ auto Result = Op1Arg + Op2Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 2,
+ WorkingOps.begin() + Loc + 4);
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ // {DW_OP_const[u, s], Const1, DW_OP_plus_uconst Const2} -> {DW_OP_constu,
+ // Const1 + Const2}
+ if (isConstOperation(Op1Raw) && Op2Raw == dwarf::DW_OP_plus_uconst) {
+ auto Result = Op1Arg + Op2Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 2,
+ WorkingOps.begin() + Loc + 4);
+ WorkingOps[Loc] = dwarf::DW_OP_constu;
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op3 = Cursor.peekNextN(2);
+ // Op2 could still match a pattern, skip iteration
+ if (!Op3) {
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+ auto Op3Raw = Op3->getOp();
+
+ // {DW_OP_const[u, s], Const1, DW_OP_const[u, s], Const2, DW_OP_[plus,
+ // minus, mul, div, shl, shr] -> {DW_OP_constu, Const1 [+, -, *, /, <<, >>]
+ // Const2}
+ if (isConstOperation(Op1Raw) && isConstOperation(Op2Raw)) {
+ auto Result = foldOperationIfPossible(Op3Raw, Op1Arg, Op2Arg);
+ if (!Result) {
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+ WorkingOps.erase(WorkingOps.begin() + Loc + 2,
+ WorkingOps.begin() + Loc + 5);
+ WorkingOps[Loc] = dwarf::DW_OP_constu;
+ WorkingOps[Loc + 1] = *Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ // {DW_OP_plus_uconst, Const1, DW_OP_const[u, s], Const1, DW_OP_plus} ->
+ // {DW_OP_plus_uconst, Const1 + Const2}
+ if (Op1Raw == dwarf::DW_OP_plus_uconst && isConstOperation(Op2Raw) &&
+ Op3Raw == dwarf::DW_OP_plus) {
+ auto Result = Op1Arg + Op2Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 2,
+ WorkingOps.begin() + Loc + 5);
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op3Arg = Op3->getArg(0);
+ // {DW_OP_const[u, s], Const1, DW_OP_plus, DW_OP_plus_uconst, Const2} ->
+ // {DW_OP_plus_uconst, Const1 + Const2}
+ if (isConstOperation(Op1Raw) && Op2Raw == dwarf::DW_OP_plus &&
+ Op3Raw == dwarf::DW_OP_plus_uconst) {
+ auto Result = Op1Arg + Op3Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 2,
+ WorkingOps.begin() + Loc + 5);
+ WorkingOps[Loc] = dwarf::DW_OP_plus_uconst;
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op4 = Cursor.peekNextN(3);
+ // Op2 and Op3 could still match a pattern, skip iteration
+ if (!Op4) {
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+ auto Op4Raw = Op4->getOp();
+
+ // {DW_OP_const[u, s], Const1, DW_OP_[plus, mul], Const2, DW_OP_[plus, mul]}
+ // -> {DW_OP_constu, Const1 [+, *] Const2, DW_OP_[plus, mul]}
+ if (isConstOperation(Op1Raw) && isConstOperation(Op3Raw) &&
+ operationsAreFoldableAndCommutative(Op2Raw, Op4Raw)) {
+ auto Result = foldOperationIfPossible(Op2Raw, Op1Arg, Op3Arg);
+ if (!Result)
+ llvm_unreachable(
+ "Something went very wrong here! This should always work");
+ WorkingOps.erase(WorkingOps.begin() + Loc + 3,
+ WorkingOps.begin() + Loc + 6);
+ WorkingOps[Loc] = dwarf::DW_OP_constu;
+ WorkingOps[Loc + 1] = *Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+ auto Op5 = Cursor.peekNextN(4);
+ if (!Op5) {
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+ auto Op5Raw = Op5->getOp();
+ auto Op5Arg = Op5->getArg(0);
+
+ // {DW_OP_const[u, s], Const1, DW_OP_plus, DW_OP_LLVM_arg, Arg1, DW_OP_plus,
+ // DW_OP_plus_uconst, Const2} -> {DW_OP_constu, Const1 + Const2, DW_OP_plus,
+ // DW_OP_LLVM_arg, Arg1, DW_OP_plus}
+ if (isConstOperation(Op1Raw) && Op3Raw == dwarf::DW_OP_LLVM_arg &&
+ Op5Raw == dwarf::DW_OP_plus_uconst && Op2Raw == Op4Raw &&
+ Op4Raw == dwarf::DW_OP_plus) {
+ auto Result = Op1Arg + Op5Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 6,
+ WorkingOps.begin() + Loc + 8);
+ WorkingOps[Loc] = dwarf::DW_OP_constu;
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op4Arg = Op4->getArg(0);
+
+ // {DW_OP_plus_uconst, Const1, DW_OP_LLVM_arg, Arg1, DW_OP_plus,
+ // DW_OP_const[u, s], Const2, DW_OP_plus} -> {DW_OP_plus_uconst, Const1 +
+ // Const2, DW_OP_LLVM_arg, Arg1, DW_OP_plus}
+ if (Op1Raw == dwarf::DW_OP_plus_uconst && Op2Raw == dwarf::DW_OP_LLVM_arg &&
+ Op3Raw == Op5Raw && Op3Raw == dwarf::DW_OP_plus &&
+ isConstOperation(Op4Raw)) {
+ auto Result = Op1Arg + Op4Arg;
+ WorkingOps.erase(WorkingOps.begin() + Loc + 5,
+ WorkingOps.begin() + Loc + 8);
+ WorkingOps[Loc + 1] = Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ auto Op6 = Cursor.peekNextN(5);
+ if (!Op6) {
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ continue;
+ }
+ auto Op6Raw = Op6->getOp();
+ // {DW_OP_const[u, s], Const1, DW_OP_[plus, mul], DW_OP_LLVM_arg, Arg1,
+ // DW_OP_[plus, mul], DW_OP_const[u, s], Const2, DW_OP_[plus, mul]} ->
+ // {DW_OP_constu, Const1 [+, *] Const2, DW_OP_[plus, mul], DW_OP_LLVM_arg,
+ // Arg1, DW_OP_[plus, mul]}
+ if (isConstOperation(Op1Raw) && Op3Raw == dwarf::DW_OP_LLVM_arg &&
+ isConstOperation(Op5Raw) &&
+ operationsAreFoldableAndCommutative(Op2Raw, Op4Raw) &&
+ operationsAreFoldableAndCommutative(Op4Raw, Op6Raw)) {
+ auto Result = foldOperationIfPossible(Op2Raw, Op1Arg, Op5Arg);
+ if (!Result)
+ llvm_unreachable(
+ "Something went very wrong here! This should always work");
+ WorkingOps.erase(WorkingOps.begin() + Loc + 6,
+ WorkingOps.begin() + Loc + 9);
+ WorkingOps[Loc] = dwarf::DW_OP_constu;
+ WorkingOps[Loc + 1] = *Result;
+ Cursor.assignNewExpr(WorkingOps);
+ Loc = 0;
+ continue;
+ }
+
+ moveCursorAndLocPos(Cursor, Loc, *Op1);
+ }
+ auto *Result = DIExpression::get(getContext(), WorkingOps);
+ assert(Result->isValid() && "concatenated expression is not valid");
+ return Result;
+}
+
uint64_t DIExpression::getNumLocationOperands() const {
uint64_t Result = 0;
for (auto ExprOp : expr_ops())
diff --git a/llvm/test/Bitcode/upgrade-dbg-addr.ll b/llvm/test/Bitcode/upgrade-dbg-addr.ll
index 40fd7db18948b57..1943c35b0059fb1 100644
--- a/llvm/test/Bitcode/upgrade-dbg-addr.ll
+++ b/llvm/test/Bitcode/upgrade-dbg-addr.ll
@@ -8,7 +8,7 @@ entry:
%num.addr = alloca i32, align 4
store i32 %num, ptr %num.addr, align 4
; CHECK-NOT: call void @llvm.dbg.addr
- ; CHECK: call void @llvm.dbg.value(metadata ptr %num.addr, metadata ![[#]], metadata !DIExpression(DW_OP_plus_uconst, 0, DW_OP_deref))
+ ; CHECK: call void @llvm.dbg.value(metadata ptr %num.addr, metadata ![[#]], metadata !DIExpression(DW_OP_deref))
call void @llvm.dbg.addr(metadata ptr %num.addr, metadata !16, metadata !DIExpression(DW_OP_plus_uconst, 0)), !dbg !17
%0 = load i32, ptr %num.addr, align 4
ret i32 %0
diff --git a/llvm/test/DebugInfo/MIR/AArch64/dbgcall-site-expr-chain.mir b/llvm/test/DebugInfo/MIR/AArch64/dbgcall-site-expr-chain.mir
index 3e2244f76c905e4..b32f7310537daf4 100644
--- a/llvm/test/DebugInfo/MIR/AArch64/dbgcall-site-expr-chain.mir
+++ b/llvm/test/DebugInfo/MIR/AArch64/dbgcall-site-expr-chain.mir
@@ -105,7 +105,7 @@ body: |
# CHECK: DW_TAG_GNU_call_site_parameter
# CHECK-NEXT: DW_AT_location (DW_OP_reg2 W2)
-# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_breg19 W19+700, DW_OP_plus_uconst 0x9, DW_OP_plus_uconst 0x50)
+# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_breg19 W19+789)
# CHECK: DW_TAG_GNU_call_site_parameter
# CHECK-NEXT: DW_AT_location (DW_OP_reg1 W1)
@@ -113,4 +113,4 @@ body: |
# CHECK: DW_TAG_GNU_call_site_parameter
# CHECK-NEXT: DW_AT_location (DW_OP_reg0 W0)
-# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_breg19 W19+100, DW_OP_plus_uconst 0x17)
+# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_breg19 W19+123)
diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
index 1570631287b2a78..2221efc73d9f468 100644
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -3120,6 +3120,388 @@ TEST_F(DIExpressionTest, get) {
EXPECT_EQ(N0WithPrependedOps, N2);
}
+TEST_F(DIExpressionTest, Fold) {
+
+ // Remove a No-op DW_OP_plus_uconst from an expression.
+ SmallVector<uint64_t, 8> Ops = {dwarf::DW_OP_plus_uconst, 0};
+ auto *Expr = DIExpression::get(Context, Ops);
+ auto *E = Expr->foldConstantMath();
+ SmallVector<uint64_t, 8> ResOps;
+ auto *ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op add from an expression.
+ Ops[0] = dwarf::DW_OP_constu;
+ Ops[1] = 0;
+ Ops.push_back(dwarf::DW_OP_plus);
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op subtract from an expression.
+ Ops[2] = dwarf::DW_OP_minus;
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op shift left from an expression.
+ Ops[2] = dwarf::DW_OP_shl;
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op shift right from an expression.
+ Ops[2] = dwarf::DW_OP_shr;
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op multiply from an expression.
+ Ops[2] = dwarf::DW_OP_mul;
+ Ops[1] = 1;
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Remove a No-op divide from an expression.
+ Ops[2] = dwarf::DW_OP_div;
+ Expr = DIExpression::get(Context, Ops);
+ E = Expr->foldConstantMath();
+ ResExpr = DIExpression::get(Context, ResOps);
+ EXPECT_EQ(E, ResExpr);
+
+ // Test fold {DW_OP_plus_uconst, Const1, DW_OP_plus_uconst, Const2} ->
+ // {DW_OP_plus_uconst, Const1 + Const2}
+ Ops[0] = dwarf::DW_OP_plus_uconst;
+ ...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/71721
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