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Store the LHS by pointer to correctly handle operations inside loops.
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@PetroZarytskyi
PetroZarytskyi committed Jul 12, 2024
1 parent f455cc6 commit 02112e9
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Showing 2 changed files with 26 additions and 25 deletions.
20 changes: 9 additions & 11 deletions lib/Differentiator/ReverseModeVisitor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2254,15 +2254,16 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
// in Lblock
beginBlock(direction::reverse);
Ldiff = Visit(L, dfdx());
auto* Lblock = endBlock(direction::reverse);

if (L->HasSideEffects(m_Context)) {
Expr* E = Ldiff.getExpr();
auto* storeE =
StoreAndRef(E, m_Context.getLValueReferenceType(E->getType()));
Ldiff.updateStmt(storeE);
GlobalStoreAndRef(BuildOp(UO_AddrOf, E));
Ldiff.updateStmt(BuildOp(UO_Deref, storeE));
}

Stmts Lblock = EndBlockWithoutCreatingCS(direction::reverse);

Expr* LCloned = Ldiff.getExpr();
// For x, AssignedDiff is _d_x, for x[i] its _d_x[i], for reference exprs
// like (x = y) it propagates recursively, so _d_x is also returned.
Expand All @@ -2271,12 +2272,9 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
return Clone(BinOp);
ResultRef = AssignedDiff;
// If assigned expr is dependent, first update its derivative;
auto Lblock_begin = Lblock->body_rbegin();
auto Lblock_end = Lblock->body_rend();

if (dfdx() && Lblock_begin != Lblock_end) {
addToCurrentBlock(*Lblock_begin, direction::reverse);
Lblock_begin = std::next(Lblock_begin);
if (dfdx() && !Lblock.empty()) {
addToCurrentBlock(*Lblock.begin(), direction::reverse);
Lblock.erase(Lblock.begin());
}

// Store the value of the LHS of the assignment in the forward pass
Expand Down Expand Up @@ -2385,8 +2383,8 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
opCode);

// Output statements from Visit(L).
for (auto it = Lblock_begin; it != Lblock_end; ++it)
addToCurrentBlock(*it, direction::reverse);
for (Stmt* S : Lblock)
addToCurrentBlock(S, direction::reverse);
} else if (opCode == BO_Comma) {
auto* zero =
ConstantFolder::synthesizeLiteral(m_Context.IntTy, m_Context, 0);
Expand Down
31 changes: 17 additions & 14 deletions test/Gradient/Assignments.C
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Original file line number Diff line number Diff line change
Expand Up @@ -414,19 +414,20 @@ double f9(double x, double y) {
//CHECK: void f9_grad(double x, double y, double *_d_x, double *_d_y) {
//CHECK-NEXT: double _d_t = 0;
//CHECK-NEXT: double _t0;
//CHECK-NEXT: double *_t1;
//CHECK-NEXT: double _t2;
//CHECK-NEXT: double t = x;
//CHECK-NEXT: _t0 = t;
//CHECK-NEXT: double &_t1 = (t *= x);
//CHECK-NEXT: _t2 = _t1;
//CHECK-NEXT: _t1 *= y;
//CHECK-NEXT: _t1 = &(t *= x);
//CHECK-NEXT: _t2 = *_t1;
//CHECK-NEXT: *_t1 *= y;
//CHECK-NEXT: _d_t += 1;
//CHECK-NEXT: {
//CHECK-NEXT: _t1 = _t2;
//CHECK-NEXT: *_t1 = _t2;
//CHECK-NEXT: double _r_d1 = _d_t;
//CHECK-NEXT: _d_t -= _r_d1;
//CHECK-NEXT: _d_t += _r_d1 * y;
//CHECK-NEXT: *_d_y += _t1 * _r_d1;
//CHECK-NEXT: *_d_y += *_t1 * _r_d1;
//CHECK-NEXT: t = _t0;
//CHECK-NEXT: double _r_d0 = _d_t;
//CHECK-NEXT: _d_t -= _r_d0;
Expand Down Expand Up @@ -473,15 +474,16 @@ double f11(double x, double y) {
//CHECK: void f11_grad(double x, double y, double *_d_x, double *_d_y) {
//CHECK-NEXT: double _d_t = 0;
//CHECK-NEXT: double _t0;
//CHECK-NEXT: double *_t1;
//CHECK-NEXT: double _t2;
//CHECK-NEXT: double t = x;
//CHECK-NEXT: _t0 = t;
//CHECK-NEXT: double &_t1 = (t = x);
//CHECK-NEXT: _t2 = _t1;
//CHECK-NEXT: _t1 = y;
//CHECK-NEXT: _t1 = &(t = x);
//CHECK-NEXT: _t2 = *_t1;
//CHECK-NEXT: *_t1 = y;
//CHECK-NEXT: _d_t += 1;
//CHECK-NEXT: {
//CHECK-NEXT: _t1 = _t2;
//CHECK-NEXT: *_t1 = _t2;
//CHECK-NEXT: double _r_d1 = _d_t;
//CHECK-NEXT: _d_t -= _r_d1;
//CHECK-NEXT: *_d_y += _r_d1;
Expand All @@ -504,23 +506,24 @@ double f12(double x, double y) {
//CHECK-NEXT: bool _cond0;
//CHECK-NEXT: double _t0;
//CHECK-NEXT: double _t1;
//CHECK-NEXT: double *_t2;
//CHECK-NEXT: double _t3;
//CHECK-NEXT: double t;
//CHECK-NEXT: _cond0 = x > y;
//CHECK-NEXT: if (_cond0)
//CHECK-NEXT: _t0 = t;
//CHECK-NEXT: else
//CHECK-NEXT: _t1 = t;
//CHECK-NEXT: double &_t2 = (_cond0 ? (t = x) : (t = y));
//CHECK-NEXT: _t3 = _t2;
//CHECK-NEXT: _t2 *= y;
//CHECK-NEXT: _t2 = &(_cond0 ? (t = x) : (t = y));
//CHECK-NEXT: _t3 = *_t2;
//CHECK-NEXT: *_t2 *= y;
//CHECK-NEXT: _d_t += 1;
//CHECK-NEXT: {
//CHECK-NEXT: _t2 = _t3;
//CHECK-NEXT: *_t2 = _t3;
//CHECK-NEXT: double _r_d2 = (_cond0 ? _d_t : _d_t);
//CHECK-NEXT: (_cond0 ? _d_t : _d_t) -= _r_d2;
//CHECK-NEXT: (_cond0 ? _d_t : _d_t) += _r_d2 * y;
//CHECK-NEXT: *_d_y += _t2 * _r_d2;
//CHECK-NEXT: *_d_y += *_t2 * _r_d2;
//CHECK-NEXT: if (_cond0) {
//CHECK-NEXT: t = _t0;
//CHECK-NEXT: double _r_d0 = _d_t;
Expand Down

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