- // We can't add or subtract two symbols.
- if ((LHS.getSymA() && RHS_A) ||
- (LHS.getSymB() && RHS_B))
- return false;
-
- const MCSymbolRefExpr *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
- const MCSymbolRefExpr *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
- if (B) {
- // If we have a negated symbol, then we must have also have a non-negated
- // symbol in order to encode the expression. We can do this check later to
- // permit expressions which eventually fold to a representable form -- such
- // as (a + (0 - b)) -- if necessary.
- if (!A)
- return false;
+ // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
+ // about dealing with modifiers. This will ultimately bite us, one day.
+ const MCSymbolRefExpr *LHS_A = LHS.getSymA();
+ const MCSymbolRefExpr *LHS_B = LHS.getSymB();
+ int64_t LHS_Cst = LHS.getConstant();
+
+ // Fold the result constant immediately.
+ int64_t Result_Cst = LHS_Cst + RHS_Cst;
+
+ assert((!Layout || Asm) &&
+ "Must have an assembler object if layout is given!");
+
+ // If we have a layout, we can fold resolved differences.
+ if (Asm) {
+ // First, fold out any differences which are fully resolved. By
+ // reassociating terms in
+ // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
+ // we have the four possible differences:
+ // (LHS_A - LHS_B),
+ // (LHS_A - RHS_B),
+ // (RHS_A - LHS_B),
+ // (RHS_A - RHS_B).
+ // Since we are attempting to be as aggressive as possible about folding, we
+ // attempt to evaluate each possible alternative.
+ AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
+ Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
+ Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
+ Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
+ Result_Cst);