Internal Compiler Error in gen_rtx_SUBREG,at emit-rtl.c:776 in CR16

Sumanth Gundapaneni
Mon Jan 31 09:38:00 GMT 2011


I have been working on port with variable register widths.
We have 12 16-bit registers and 4 32-bit registers.
Registers r0 - r11 are 16-b wide and can be paired to form a 32-b register.
Registers r12,r13,r14 and r15 are 32-bit wide and out of which 
r12 - argument pointer register.
r13 - frame pointer register.
r14 - return address register.
r15 - stack pointer register. 

I faced a regression in gcc-torture test case "20070905-1.c"
when I compile the code with -O2 or higher the test case fails
with "internal compiler error: in gen_rtx_SUBREG, at emit-rtl.c:776"

After analyzing the rtl dump, I figured out that below mentioned dump is the 
reason for the failure.
(insn 46 14 47 4 20070905-1.c:17 (set (reg:HI 3 r3)
        (subreg:HI (reg/f:SI 13 r13) 0)) 64 {*movhi_short} (nil))

(insn 47 46 18 4 20070905-1.c:17 (set (reg:HI 4 r4 [+2 ])
        (subreg:HI (reg/f:SI 13 r13) 2)) 64 {*movhi_short} (nil))

The insn  47 with subreg byte value of 2 causes the ICE in 
function gen_rtx_SUBREG.
" gcc_assert (validate_subreg (mode, GET_MODE (reg), reg, offset)); "

You can find the current implementation of cr16 at the following link

In addition to the patch I have made couple of changes suggested by 
Richard Henderson.

One among them is :: 
  (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO)           \
   ? reg_classes_intersect_p (LONG_REGS, (CLASS))        \
   : 0)
>> LONG_REGS are 32-bit registers

Please let me know if you need further information.
Your help in this regard is highly appreciated.

Thanks and Regards,
Sumanth G


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