[Bug rtl-optimization/63823] [5.0 Regression] MIPS will not build due to LRA ICE with 64 bit ABI

[robert.suchanek at imgtec dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63823

--- Comment #5 from Robert Suchanek <robert.suchanek at imgtec dot com> ---
It appears that enabling the debug info can trigger the ICE. In the testcase,
after the patch, an instruction 1136 gets deleted and all references to pseudo
704 meant to be updated.

The following change in process_bb_lives () triggers the assertion later in the
pass.

+             EXECUTE_IF_SET_IN_BITMAP
+               (&lra_reg_info[dst_regno].insn_bitmap, 0, uid, bi)
+               {
+                 insn = lra_insn_recog_data[uid]->insn;
+                 lra_substitute_pseudo_within_insn (insn, dst_regno,
+                                                    SET_SRC (set));
+                 lra_update_insn_regno_info (insn);
+               }

On the first iteration, the list of insns using pseudo 704 is correct:

(gdb) call debug_bitmap(&lra_reg_info[704].insn_bitmap)

first = 0x188b720 current = 0x188b770 indx = 3
        0x188b720 next = 0x188b770 prev = (nil) indx = 2
                bits = { 343 }
        0x188b770 next = (nil) prev = 0x188b720 indx = 3
                bits = { 384 }

Insn 343 gets updated, pseudo 704 is replaced with original pseudo 234.
However, the call to lra_update_insn_regno_info destroys the remaining
references to pseudo 704 via invalidate_insn_data_regno_info so we end up with
the following:

(gdb) call debug_bitmap(&lra_reg_info[704].insn_bitmap)

first = 0x1855770 current = 0x1855770 indx = 3         
        0x1855770 next = (nil) prev = (nil) indx = 3   
                bits = { 384 }

The next iteration(s) in EXECUTE_IF_SET_IN_BITMAP will not happen as
bmp_iter_set () returns false. Insn 384 is left unchanged and the compiler
fails later on assertion.