Here's an example of bad assumptions. The current code calculates the
subreg location BEFORE checking to see if such a subreg is legal.
This patch moved the legality check before the location calculations.
With this patch, I can build gcc's libraries and newlib, but I haven't
run full regressions on it yet.
Index: reload1.c
===================================================================
--- reload1.c (revision 121130)
+++ reload1.c (working copy)
@@ -5653,7 +5653,16 @@ choose_reload_regs (struct insn_chain *c
regno = subreg_regno (rld[r].in);
#endif
- if (regno >= 0 && reg_last_reload_reg[regno] != 0)
+ if (regno >= 0
+ && reg_last_reload_reg[regno] != 0
+#ifdef CANNOT_CHANGE_MODE_CLASS
+ /* Verify that the register it's in can be used in
+ mode MODE. */
+ && !REG_CANNOT_CHANGE_MODE_P (REGNO
(reg_last_reload_reg[regno]),
+ GET_MODE
(reg_last_reload_reg[regno]),
+ mode)
+#endif
+ )
{
enum reg_class class = rld[r].class, last_class;
rtx last_reg = reg_last_reload_reg[regno];
@@ -5673,13 +5682,6 @@ choose_reload_regs (struct insn_chain *c
if ((GET_MODE_SIZE (GET_MODE (last_reg))
>= GET_MODE_SIZE (need_mode))
-#ifdef CANNOT_CHANGE_MODE_CLASS
- /* Verify that the register in "i" can be obtained
- from LAST_REG. */
- && !REG_CANNOT_CHANGE_MODE_P (REGNO (last_reg),
- GET_MODE (last_reg),
- mode)
-#endif
&& reg_reloaded_contents[i] == regno
&& TEST_HARD_REG_BIT (reg_reloaded_valid, i)
&& HARD_REGNO_MODE_OK (i, rld[r].mode)
