On 12/11/20 1:48 PM, Maciej W. Rozycki wrote:
> Handle constant 0 passed to the QMATH DImode add/sub handler such as
> with:
>
> #2 0x0000000011d409b0 in gen_adddi3 (operand0=0x7ffff5c0a128,
> operand1=0x7ffff5c60480, operand2=0x7ffff5c60470)
> at .../gcc/config/vax/vax.md:755
> 755 "vax_expand_addsub_di_operands (operands, PLUS); DONE;")
> (gdb) pr operand0
> (reg:DI 31)
> (gdb) pr operand1
> (const_int 0 [0])
> (gdb) pr operand2
> (const_int -1 [0xffffffffffffffff])
> (gdb)
>
> causing an assertion in `vax_expand_addsub_di_operands':
>
> gcc_assert (operands[1] != const0_rtx || code == MINUS);
>
> to trigger:
>
> during RTL pass: expand
> .../gcc/testsuite/gcc.c-torture/compile/sync-1.c: In function
> 'test_op_ignore':
> .../gcc/testsuite/gcc.c-torture/compile/sync-1.c:33:10: internal compiler
> error: in vax_expand_addsub_di_operands, at config/vax/vax.c:2080
> 0x11815003 vax_expand_addsub_di_operands(rtx_def**, rtx_code)
> .../gcc/config/vax/vax.c:2080
> 0x11d409af gen_adddi3(rtx_def*, rtx_def*, rtx_def*)
> .../gcc/config/vax/vax.md:755
> 0x10ea2763 rtx_insn* insn_gen_fn::operator()<rtx_def*, rtx_def*,
> rtx_def*>(rtx_def*, rtx_def*, rtx_def*) const
> .../gcc/recog.h:304
> 0x10f7fc8f maybe_gen_insn(insn_code, unsigned int, expand_operand*)
> .../gcc/optabs.c:7402
> 0x10f67f8b expand_binop_directly
> .../gcc/optabs.c:1122
> 0x10f684cf expand_binop(machine_mode, optab_tag, rtx_def*, rtx_def*,
> rtx_def*, int, optab_methods)
> .../gcc/optabs.c:1209
> 0x10f6fb4f expand_unop(machine_mode, optab_tag, rtx_def*, rtx_def*, int)
> .../gcc/optabs.c:3013
> 0x10f6c493 expand_simple_unop(machine_mode, rtx_code, rtx_def*, rtx_def*, int)
> .../gcc/optabs.c:2200
> 0x10f7e2f3 expand_atomic_fetch_op(rtx_def*, rtx_def*, rtx_def*, rtx_code,
> memmodel, bool)
> .../gcc/optabs.c:7021
> 0x107f7523 expand_builtin_sync_operation
> .../gcc/builtins.c:7605
> 0x107ff547 expand_builtin(tree_node*, rtx_def*, rtx_def*, machine_mode, int)
> .../gcc/builtins.c:9430
> 0x10acda63 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
> expand_modifier, rtx_def**, bool)
> .../gcc/expr.c:11249
> 0x10abeb9f expand_expr_real(tree_node*, rtx_def*, machine_mode,
> expand_modifier, rtx_def**, bool)
> .../gcc/expr.c:8486
> 0x1085606b expand_expr
> .../gcc/expr.h:282
> 0x1086157f expand_call_stmt
> .../gcc/cfgexpand.c:2709
> 0x10865ab7 expand_gimple_stmt_1
> .../gcc/cfgexpand.c:3713
> 0x108662fb expand_gimple_stmt
> .../gcc/cfgexpand.c:3877
> 0x10870387 expand_gimple_basic_block
> .../gcc/cfgexpand.c:5918
> 0x10872b6b execute
> .../gcc/cfgexpand.c:6602
> Please submit a full bug report,
> with preprocessed source if appropriate.
> Please include the complete backtrace with any bug report.
> See <https://gcc.gnu.org/bugs/> for instructions.
> compiler exited with status 1
> FAIL: gcc.c-torture/compile/sync-1.c -O0 (internal compiler error)
>
> causing numerous failures in regression testing.
>
> While requesting an addition operation to be produced for the constant
> operands of 0 and -1 may seem silly, technically there is nothing wrong
> with it, and non-QMATH code (as with the `-mno-qmath' option) has no
> issues with that, so neither should QMATH code. This operation will
> normally be folded in later passes anyway.
>
> Observe then, that adding or subtracting constant 0 amounts to a move
> (and we even have a machine instruction available to do that with a
> single operation) so handle the case explicitly, swapping the addends if
> so required, removing the assertion failure and along with that 70 test
> suite failures like:
>
> FAIL: gcc.c-torture/compile/sync-1.c -O0 (internal compiler error)
> FAIL: gcc.c-torture/compile/sync-1.c -O0 fetch_and_nand (test for
> warnings, line )
> FAIL: gcc.c-torture/compile/sync-1.c -O0 nand_and_fetch (test for
> warnings, line )
> FAIL: gcc.c-torture/compile/sync-1.c -O0 (test for excess errors)
> FAIL: gcc.c-torture/compile/sync-2.c -O0 (internal compiler error)
> FAIL: gcc.c-torture/compile/sync-2.c -O0 (test for warnings, line )
> FAIL: gcc.c-torture/compile/sync-2.c -O0 (test for excess errors)
> FAIL: gcc.c-torture/compile/sync-3.c -O0 (internal compiler error)
> FAIL: gcc.c-torture/compile/sync-3.c -O0 (test for warnings, line )
> FAIL: gcc.c-torture/compile/sync-3.c -O0 (test for excess errors)
>
> and similarly across all the other optimization levels and compilation
> options covered.
>
> gcc/
> * config/vax/vax.c (vax_expand_addsub_di_operands): Handle the
> addition or subtraction of 0.
OK, though I would have generally expected something to catch this earlier.
jeff
