gcc-4.9 errors out on valid inline asm

[Arnd Bergmann]

Found while building an arm32 kernel

~/cross/bin/arm-linux-gnueabihf-gcc-4.9.0 -march=armv7-a -O2 -c -x c - <<< 'int g(void) { unsigned i, j; asm("// %0 %1" : "=r" (i), "=r"(j)); return i; }'
<stdin>: In function 'g':
<stdin>:1:30: error: invalid 'asm': operand number out of range

~/cross/bin/arm-linux-gnueabihf-gcc-4.9.0 --version
arm-linux-gnueabihf-gcc-4.9.0 (GCC) 4.9.0 20140324 (experimental)

[Zhenqiang Chen (zhenqiang-chen)]

I can confirm it with trunk. There is no issue for Linaro 4.8 release.

Root cause: rtx_cost change in trunk triggers the bug. The check of check_asm_operands should be enhanced.

I will raise it to upstream and try to fix it.

[Zhenqiang Chen (zhenqiang-chen)]

Found while building an arm32 kernel

//fail.c
int g(void)
{
  unsigned i, j;
  asm("// %0 %1" : "=r" (i), "=r"(j));
  return i;
}

arm-linux-gnueabihf-gcc -march=armv7-a -O2 -c fail.c
fail.c: In function ‘g’:
fail.c:4:3: error: invalid 'asm': operand number out of range

Root cause: "cse1" generates illegal asm instruction since check_asm_operands does not check the number of expected operands.

i.e. "cse1" changes code from
(insn 5 2 6 2 (parallel [
            (set (reg:SI 114 [ i ])
                (asm_operands:SI ("// %0 %1") ("=r") 0 []
                     []
                     [] fail.c:4))
            (set (reg:SI 115 [ j ])
                (asm_operands:SI ("// %0 %1") ("=r") 1 []
                     []
                     [] fail.c:4))
        ]) fail.c:4 -1
     (nil))
(insn 6 5 8 2 (set (reg/v:SI 110 [ i ])
        (reg:SI 114 [ i ])) fail.c:4 664 {*thumb2_movsi_vfp}
     (nil))
to

(insn 12 2 13 2 (set (reg/i:SI 0 r0)
        (asm_operands:SI ("// %0 %1") ("=r") 0 []
             []
             [] fail.c:4)) fail.c:6 -1
     (nil))

No error for x86-64 and arm gcc-4.8. ARM rtx_cost changes in 4.9 trigger this optimization.

A patch to enhance check_asm_operands is sent out for review.

[Jakub-gcc (jakub-gcc)]

Supposedly introduced by r203160 which made inline asm with no input operands appear as having zero cost.

Alternate patch posted at http://gcc.gnu.org/ml/gcc-patches/2014-04/msg00512.html

[Jakub-gcc (jakub-gcc)]

Author: jakub
Date: Fri Apr 11 10:11:01 2014
New Revision: 209293

URL: http://gcc.gnu.org/viewcvs?rev=209293&root=gcc&view=rev
Log:
 PR rtl-optimization/60663
 * cse.c (cse_insn): Set src_volatile on ASM_OPERANDS in
 PARALLEL.

 * gcc.target/arm/pr60663.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/arm/pr60663.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cse.c
    trunk/gcc/testsuite/ChangeLog

[Jakub-gcc (jakub-gcc)]

Should be fixed now.

[Arnd Bergmann (arnd-arndb)]

Fix tested successfully

[Arnd Bergmann (arnd-arndb)]

Looks good now, I have resumed ARM kernel build testing with gcc-4.9 now and don't see this any more. There is one new bug that came up instead but it seems unrelated. I'll open a new ticket for that.

[Ktkachov (ktkachov)]

Author: ktkachov
Date: Tue Apr 15 14:04:06 2014
New Revision: 209419

URL: http://gcc.gnu.org/viewcvs?rev=209419&root=gcc&view=rev
Log:

 PR rtl-optimization/60663
 * config/arm/arm.c (arm_new_rtx_costs): Improve ASM_OPERANDS case,
 avoid 0 cost.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/arm/arm.c

[Yroux (yroux)]

Author: yroux
Date: Thu Jun 12 09:13:57 2014
New Revision: 211497

URL: http://gcc.gnu.org/viewcvs?rev=211497&root=gcc&view=rev
Log:
2014-05-23 Yvan Roux <email address hidden>

       Backport from trunk r209419.
       2014-04-15 Kyrylo Tkachov <email address hidden>

       PR rtl-optimization/60663
       * config/arm/arm.c (arm_new_rtx_costs): Improve ASM_OPERANDS case,
       avoid 0 cost.

Modified:
    branches/linaro/gcc-4_9-branch/gcc/ChangeLog.linaro
    branches/linaro/gcc-4_9-branch/gcc/config/arm/arm.c

[Michael Collison (michael-collison)]

Fixed in June release of Linaro GCC 4.9

[Jakub-gcc (jakub-gcc)]

Author: jakub
Date: Fri Jan 23 19:55:16 2015
New Revision: 220059

URL: https://gcc.gnu.org/viewcvs?rev=220059&root=gcc&view=rev
Log:
 PR rtl-optimization/63637
 PR rtl-optimization/60663
 * cse.c (merge_equiv_classes): Set new_elt->cost to MAX_COST
 if elt->cost is MAX_COST for ASM_OPERANDS.
 (find_sets_in_insn): Fix up comment typo.
 (cse_insn): Don't set src_volatile for all non-volatile
 ASM_OPERANDS in PARALLELs, but just those with multiple outputs
 or with "memory" clobber. Set elt->cost to MAX_COST
 for ASM_OPERANDS in PARALLEL. Set src_elt->cost to MAX_COST
 if new_src is ASM_OPERANDS and elt->cost is MAX_COST.

 * gcc.dg/pr63637-1.c: New test.
 * gcc.dg/pr63637-2.c: New test.
 * gcc.dg/pr63637-3.c: New test.
 * gcc.dg/pr63637-4.c: New test.
 * gcc.dg/pr63637-5.c: New test.
 * gcc.dg/pr63637-6.c: New test.
 * gcc.target/i386/pr63637-1.c: New test.
 * gcc.target/i386/pr63637-2.c: New test.
 * gcc.target/i386/pr63637-3.c: New test.
 * gcc.target/i386/pr63637-4.c: New test.
 * gcc.target/i386/pr63637-5.c: New test.
 * gcc.target/i386/pr63637-6.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr63637-1.c
    trunk/gcc/testsuite/gcc.dg/pr63637-2.c
    trunk/gcc/testsuite/gcc.dg/pr63637-3.c
    trunk/gcc/testsuite/gcc.dg/pr63637-4.c
    trunk/gcc/testsuite/gcc.dg/pr63637-5.c
    trunk/gcc/testsuite/gcc.dg/pr63637-6.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-1.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-2.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-3.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-4.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-5.c
    trunk/gcc/testsuite/gcc.target/i386/pr63637-6.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cse.c
    trunk/gcc/testsuite/ChangeLog

[Jakub-gcc (jakub-gcc)]

Author: jakub
Date: Sun Feb 1 17:33:19 2015
New Revision: 220323

URL: https://gcc.gnu.org/viewcvs?rev=220323&root=gcc&view=rev
Log:
 Backported from mainline
 2015-01-23 Jakub Jelinek <email address hidden>

 PR rtl-optimization/63637
 PR rtl-optimization/60663
 * cse.c (merge_equiv_classes): Set new_elt->cost to MAX_COST
 if elt->cost is MAX_COST for ASM_OPERANDS.
 (find_sets_in_insn): Fix up comment typo.
 (cse_insn): Don't set src_volatile for all non-volatile
 ASM_OPERANDS in PARALLELs, but just those with multiple outputs
 or with "memory" clobber. Set elt->cost to MAX_COST
 for ASM_OPERANDS in PARALLEL. Set src_elt->cost to MAX_COST
 if new_src is ASM_OPERANDS and elt->cost is MAX_COST.

 * gcc.dg/pr63637-1.c: New test.
 * gcc.dg/pr63637-2.c: New test.
 * gcc.dg/pr63637-3.c: New test.
 * gcc.dg/pr63637-4.c: New test.
 * gcc.dg/pr63637-5.c: New test.
 * gcc.dg/pr63637-6.c: New test.
 * gcc.target/i386/pr63637-1.c: New test.
 * gcc.target/i386/pr63637-2.c: New test.
 * gcc.target/i386/pr63637-3.c: New test.
 * gcc.target/i386/pr63637-4.c: New test.
 * gcc.target/i386/pr63637-5.c: New test.
 * gcc.target/i386/pr63637-6.c: New test.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-1.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-2.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-3.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-4.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-5.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr63637-6.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-1.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-2.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-3.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-4.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-5.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr63637-6.c
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/cse.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog