bunda@cs.utexas.edu (John Bunda) (11/11/88)
This bug occurs in my port to our experimental machine (METRIC),
I haven't checked to see if it occurs for other little-endian
memory machines.
The problem occurs when a global memory reference is used in a
shorter mode than its natural one; in this case, when adding
a global int to a local short. The program test.c:
extern int x;
bad_load()
{
register short y = 5;
y += x;
return y;
}
TRULY_NOOP_TRUNCATION is defined as 0, and truncation insns
are defined only on
The code generated for my machine with incorrect code noted:
%% Metric gcc output
%% gcc level 1.30 11/10/88
.text
.align 2
LC0:
.long _x
.align 1
.globl _test
_test:
% test (C function)
% stack usage: 0 bytes argument overflow
% 32 bytes register save
% 0 bytes local stack frame
.using _test,r2
stm r1,r8,-128(r4)
move r2,r25
lda r3,-128(r4)
lda r4,-128(r4)
ldi r6,5
ld r7,LC0 <----- load address of x (declared extern int)
ldh r8,0(r7) <----- but load wrong halfword - should be 2(r7)
move r7,r6
shli r7,16
shrai r7,16
shli r8,16
shrai r8,16
add r7,r8
move r6,r7
move r26,r6
shli r26,16
shrai r26,16
j L1
L1:
ldm r1,r8,0(r3)
return
.drop r2
% End of function test
%
*******
Here is the RTL from: gcc -S -dr test.c
*******
;; Function test
(note 1 0 2 "" -1)
(note 2 1 3 "" -2)
(insn 3 2 4 (use (reg/v:HI 32)) -1 (nil)
(nil))
(insn 4 3 5 (set (reg/v:HI 32)
(const_int 5)) -1 (nil)
(nil))
(insn 5 4 6 (set (reg:SI 33)
(mem:SI (symbol_ref/u:SI ("*LC0")))) -1 (nil)
(expr_list:SI (symbol_ref:SI ("x"))
(nil)))
(insn 6 5 7 (set (reg:HI 34)
(mem:HI (reg:SI 33))) -1 (nil) <- note ref of memory in wrong mode here
(nil))
(insn 7 6 8 (set (reg:SI 35)
(sign_extend:SI (reg/v:HI 32))) -1 (nil)
(nil))
(insn 8 7 10 (set (reg:SI 36)
(sign_extend:SI (reg:HI 34))) -1 (nil)
(nil))
(insn 10 8 11 (set (reg:SI 37)
(plus:SI (reg:SI 35)
(reg:SI 36))) -1 (nil)
(nil))
(insn 11 10 12 (set (reg/v:HI 32)
(subreg:HI (reg:SI 37) 0)) -1 (nil)
(nil))
(insn 12 11 13 (set (reg/i:SI 26)
(sign_extend:SI (reg/v:HI 32))) -1 (nil)
(nil))
(insn 13 12 14 (use (reg/i:SI 26)) -1 (nil)
(nil))
(jump_insn 14 13 15 (set (pc)
(label_ref 19)) -1 (nil)
(nil))
(barrier 15 14 16)
(note 16 15 17 "" -3)
(insn 17 16 18 (use (reg/v:HI 32)) -1 (nil)
(nil))
(note 18 17 19 "" -6)
(code_label 19 18 0 1)
**** end of RTL ****
Thanks!
-John
..................................
John Bunda UT CS Dept.
bunda@cs.utexas.edu Austin, Texas bunda@cs.utexas.edu (John Bunda) (11/11/88)
Apologies - I located the problem described in the previous posting, and it is not a gcc problem. please ignore it. -john -- ................................... John Bunda UT CS Dept. bunda@cs.utexas.edu Austin, Texas