+/* LOC is a REG or MEM that we would like to track if possible.
+ If EXPR is null, we don't know what expression LOC refers to,
+ otherwise it refers to EXPR + OFFSET. STORE_REG_P is true if
+ LOC is an lvalue register.
+
+ Return true if EXPR is nonnull and if LOC, or some lowpart of it,
+ is something we can track. When returning true, store the mode of
+ the lowpart we can track in *MODE_OUT (if nonnull) and its offset
+ from EXPR in *OFFSET_OUT (if nonnull). */
+
+static bool
+track_loc_p (rtx loc, tree expr, HOST_WIDE_INT offset, bool store_reg_p,
+ enum machine_mode *mode_out, HOST_WIDE_INT *offset_out)
+{
+ enum machine_mode mode;
+
+ if (expr == NULL || !track_expr_p (expr))
+ return false;
+
+ /* If REG was a paradoxical subreg, its REG_ATTRS will describe the
+ whole subreg, but only the old inner part is really relevant. */
+ mode = GET_MODE (loc);
+ if (REG_P (loc) && !HARD_REGISTER_NUM_P (ORIGINAL_REGNO (loc)))
+ {
+ enum machine_mode pseudo_mode;
+
+ pseudo_mode = PSEUDO_REGNO_MODE (ORIGINAL_REGNO (loc));
+ if (GET_MODE_SIZE (mode) > GET_MODE_SIZE (pseudo_mode))
+ {
+ offset += byte_lowpart_offset (pseudo_mode, mode);
+ mode = pseudo_mode;
+ }
+ }
+
+ /* If LOC is a paradoxical lowpart of EXPR, refer to EXPR itself.
+ Do the same if we are storing to a register and EXPR occupies
+ the whole of register LOC; in that case, the whole of EXPR is
+ being changed. We exclude complex modes from the second case
+ because the real and imaginary parts are represented as separate
+ pseudo registers, even if the whole complex value fits into one
+ hard register. */
+ if ((GET_MODE_SIZE (mode) > GET_MODE_SIZE (DECL_MODE (expr))
+ || (store_reg_p
+ && !COMPLEX_MODE_P (DECL_MODE (expr))
+ && hard_regno_nregs[REGNO (loc)][DECL_MODE (expr)] == 1))
+ && offset + byte_lowpart_offset (DECL_MODE (expr), mode) == 0)
+ {
+ mode = DECL_MODE (expr);
+ offset = 0;
+ }
+
+ if (offset < 0 || offset >= MAX_VAR_PARTS)
+ return false;
+
+ if (mode_out)
+ *mode_out = mode;
+ if (offset_out)
+ *offset_out = offset;
+ return true;
+}
+
+/* Return the MODE lowpart of LOC, or null if LOC is not something we
+ want to track. When returning nonnull, make sure that the attributes
+ on the returned value are updated. */
+
+static rtx
+var_lowpart (enum machine_mode mode, rtx loc)
+{
+ unsigned int offset, reg_offset, regno;
+
+ if (!REG_P (loc) && !MEM_P (loc))
+ return NULL;
+
+ if (GET_MODE (loc) == mode)
+ return loc;
+
+ offset = byte_lowpart_offset (mode, GET_MODE (loc));
+
+ if (MEM_P (loc))
+ return adjust_address_nv (loc, mode, offset);
+
+ reg_offset = subreg_lowpart_offset (mode, GET_MODE (loc));
+ regno = REGNO (loc) + subreg_regno_offset (REGNO (loc), GET_MODE (loc),
+ reg_offset, mode);
+ return gen_rtx_REG_offset (loc, mode, regno, offset);
+}
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