PR target/58901: reload: Handle SUBREG of MEM with a mode-dependent address

PR target/58901: reload: Handle SUBREG of MEM with a mode-dependent address

Fix an ICE with the handling of RTL expressions like:

(subreg:QI (mem/c:SI (plus:SI (plus:SI (mult:SI (reg/v:SI 0 %r0 [orig:67 i ] [67])
                    (const_int 4 [0x4]))
                (reg/v/f:SI 7 %r7 [orig:59 doacross ] [59]))
            (const_int 40 [0x28])) [1 MEM[(unsigned int *)doacross_63 + 40B + i_106 * 4]+0 S4 A32]) 0)

that causes the compilation of libgomp to fail:

during RTL pass: reload
.../libgomp/ordered.c: In function 'GOMP_doacross_wait':
.../libgomp/ordered.c:507:1: internal compiler error: in change_address_1, at emit-rtl.c:2275
  507 | }
      | ^
0x10a3462b change_address_1
	.../gcc/emit-rtl.c:2275
0x10a353a7 adjust_address_1(rtx_def*, machine_mode, poly_int<1u, long>, int, int, int, poly_int<1u, long>)
	.../gcc/emit-rtl.c:2409
0x10ae2993 alter_subreg(rtx_def**, bool)
	.../gcc/final.c:3368
0x10ae25cf cleanup_subreg_operands(rtx_insn*)
	.../gcc/final.c:3322
0x110922a3 reload(rtx_insn*, int)
	.../gcc/reload1.c:1232
0x10de2bf7 do_reload
	.../gcc/ira.c:5812
0x10de3377 execute
	.../gcc/ira.c:5986

in a `vax-netbsdelf' build, where an attempt is made to change the mode
of the contained memory reference to the mode of the containing SUBREG.
Such RTL expressions are produced by the VAX shift and rotate patterns
(`ashift', `ashiftrt', `rotate', `rotatert') where the count operand
always has the QI mode regardless of the mode, either SI or DI, of the
datum shifted or rotated.

Such a mode change cannot work where the memory reference uses the
indexed addressing mode, where a multiplier is implied that in the VAX
ISA depends on the width of the memory access requested and therefore
changing the machine mode would change the address calculation as well.

Avoid the attempt then by forcing the reload of any SUBREGs containing
a mode-dependent memory reference, also fixing these regressions:

FAIL: gcc.c-torture/compile/pr46883.c   -Os  (internal compiler error)
FAIL: gcc.c-torture/compile/pr46883.c   -Os  (test for excess errors)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2  (internal compiler error)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/execute/20120808-1.c   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  (internal compiler error)
FAIL: gcc.c-torture/execute/20120808-1.c   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  (test for excess errors)
FAIL: gcc.c-torture/execute/20120808-1.c   -O3 -g  (internal compiler error)
FAIL: gcc.c-torture/execute/20120808-1.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (internal compiler error)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (test for excess errors)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (internal compiler error)
FAIL: gcc.c-torture/execute/20120808-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
FAIL: gcc.dg/20050629-1.c (internal compiler error)
FAIL: gcc.dg/20050629-1.c (test for excess errors)
FAIL: c-c++-common/torture/pr53505.c   -Os  (internal compiler error)
FAIL: c-c++-common/torture/pr53505.c   -Os  (test for excess errors)
FAIL: gfortran.dg/coarray_failed_images_1.f08   -Os  (internal compiler error)
FAIL: gfortran.dg/coarray_stopped_images_1.f08   -Os  (internal compiler error)

With test case #0 included it causes a reload with:

(insn 15 14 16 4 (set (reg:SI 31)
        (ashift:SI (const_int 1 [0x1])
            (subreg:QI (reg:SI 30 [ MEM[(int *)s_8(D) + 4B + _5 * 4] ]) 0))) "pr58901-0.c":15:12 94 {ashlsi3}
     (expr_list:REG_DEAD (reg:SI 30 [ MEM[(int *)s_8(D) + 4B + _5 * 4] ])
        (nil)))

as follows:

Reloads for insn # 15
Reload 0: reload_in (SI) = (reg:SI 30 [ MEM[(int *)s_8(D) + 4B + _5 * 4] ])
	ALL_REGS, RELOAD_FOR_INPUT (opnum = 2)
	reload_in_reg: (reg:SI 30 [ MEM[(int *)s_8(D) + 4B + _5 * 4] ])
	reload_reg_rtx: (reg:SI 5 %r5)

resulting in:

(insn 37 14 15 4 (set (reg:SI 5 %r5)
        (mem/c:SI (plus:SI (plus:SI (mult:SI (reg/v:SI 1 %r1 [orig:25 i ] [25])
                        (const_int 4 [0x4]))
                    (reg/v/f:SI 4 %r4 [orig:29 s ] [29]))
                (const_int 4 [0x4])) [1 MEM[(int *)s_8(D) + 4B + _5 * 4]+0 S4 A32])) "pr58901-0.c":15:12 12 {movsi_2}
     (nil))
(insn 15 37 16 4 (set (reg:SI 2 %r2 [31])
        (ashift:SI (const_int 1 [0x1])
            (reg:QI 5 %r5))) "pr58901-0.c":15:12 94 {ashlsi3}
     (nil))

and assembly like:

.L3:
	movl 4(%r4)[%r1],%r5
	ashl %r5,$1,%r2
	xorl2 %r2,%r0
	incl %r1
	cmpl %r1,%r3
	jneq .L3

produced for the loop, providing optimization has been enabled.

Likewise with test case #1 the reload of:

(insn 17 16 18 4 (set (reg:SI 34)
        (and:SI (subreg:SI (reg/v:DI 27 [ t ]) 4)
            (const_int 1 [0x1]))) "pr58901-1.c":18:20 77 {*andsi_const_int}
     (expr_list:REG_DEAD (reg/v:DI 27 [ t ])
        (nil)))

is as follows:

Reloads for insn # 17
Reload 0: reload_in (DI) = (reg/v:DI 27 [ t ])
	reload_out (SI) = (reg:SI 2 %r2 [34])
	ALL_REGS, RELOAD_OTHER (opnum = 0)
	reload_in_reg: (reg/v:DI 27 [ t ])
	reload_out_reg: (reg:SI 2 %r2 [34])
	reload_reg_rtx: (reg:DI 4 %r4)

resulting in:

(insn 40 16 17 4 (set (reg:DI 4 %r4)
        (mem/c:DI (plus:SI (mult:SI (reg/v:SI 1 %r1 [orig:26 i ] [26])
                    (const_int 8 [0x8]))
                (reg/v/f:SI 3 %r3 [orig:30 s ] [30])) [1 MEM[(const struct s *)s_13(D) + _7 * 8]+0 S8 A32])) "pr58901-1.c":18:20 11 {movdi}
     (nil))
(insn 17 40 41 4 (set (reg:SI 4 %r4)
        (and:SI (reg:SI 5 %r5 [+4 ])
            (const_int 1 [0x1]))) "pr58901-1.c":18:20 77 {*andsi_const_int}
     (nil))

and assembly like:

.L3:
	movq (%r3)[%r1],%r4
	bicl3 $-2,%r5,%r4
	addl2 %r4,%r0
	jaoblss %r0,%r1,.L3

First posted at: <https://gcc.gnu.org/ml/gcc/2014-06/msg00060.html>.

2020-12-05  Matt Thomas  <matt@3am-software.com>
	    Maciej W. Rozycki  <macro@linux-mips.org>

	gcc/
	PR target/58901
	* reload.c (push_reload): Also reload the inner expression of a
	SUBREG for pseudos associated with a mode-dependent memory
	reference.
	(find_reloads): Force a reload likewise.

2020-12-05  Maciej W. Rozycki  <macro@linux-mips.org>

	gcc/testsuite/
	PR target/58901
	* gcc.c-torture/compile/pr58901-0.c: New test.
	* gcc.c-torture/compile/pr58901-1.c: New test.