> Ok, so it's folding > > x == 127 ? .gnat_rcheck_CE_Overflow_Check ("overflow_sum3.adb", 14);, 0 : > (short_short_integer) x + 1 > > <= 127 > > where op0 (the COND_EXPR) does not have TREE_SIDE_EFFECTS set but > its operand 1 has: > > (gdb) p debug_tree (op0) > <cond_expr 0x7ffff68cbf90 > type <integer_type 0x7ffff6572dc8 short_short_integer sizes-gimplified > public visited QI > size <integer_cst 0x7ffff68ccca8 constant visited 8> > unit size <integer_cst 0x7ffff68cccc0 constant visited 1> > align 8 symtab 0 alias set -1 canonical type 0x7ffff6572dc8 > precision 8 min <integer_cst 0x7ffff656a678 -128> max <integer_cst > 0x7ffff656a6c0 127> context <translation_unit_decl 0x7ffff7ff81e0 D.24> RM > size <integer_cst 0x7ffff68ccca8 8> > chain <type_decl 0x7ffff6900b48 short_short_integer>> > > arg 0 <eq_expr 0x7ffff6573938 > ... > arg 1 <compound_expr 0x7ffff65739b0 type <integer_type 0x7ffff6572dc8 > short_short_integer> > side-effects > ... > arg 2 <plus_expr 0x7ffff6573910 type <integer_type 0x7ffff6572dc8 > short_short_integer> > ... > > that's unexpected to the code generated by genmatch and I don't see > how omit_one_operand would handle that either.
The old code was propagating the comparison inside the arms of COND_EXPR (fold_binary_op_with_conditional_arg) before applying the transformation: if ((short_short_integer) x == 127 ? .gnat_rcheck_CE_Overflow_Check ("overflow_sum3.adb", 14);, 1 : 1) The new code does the reverse, but the old behavior can be easily restored: Index: fold-const.c =================================================================== --- fold-const.c (revision 227729) +++ fold-const.c (working copy) @@ -9025,10 +9025,6 @@ fold_binary_loc (location_t loc, && tree_swap_operands_p (arg0, arg1, true)) return fold_build2_loc (loc, swap_tree_comparison (code), type, op1, op0); - tem = generic_simplify (loc, code, type, op0, op1); - if (tem) - return tem; - /* ARG0 is the first operand of EXPR, and ARG1 is the second operand. First check for cases where an arithmetic operation is applied to a @@ -9114,6 +9110,10 @@ fold_binary_loc (location_t loc, } } + tem = generic_simplify (loc, code, type, op0, op1); + if (tem) + return tem; + switch (code) { case MEM_REF: is sufficient to fix the regression. > The COND_EXPR is originally built with TREE_SIDE_EFFECTS set but: > > Hardware watchpoint 7: *$43 > > Old value = 65595 > New value = 59 > emit_check (gnu_cond=<eq_expr 0x7ffff6573938>, > gnu_expr=<plus_expr 0x7ffff6573910>, reason=10, gnat_node=2320) > at /space/rguenther/src/svn/trunk/gcc/ada/gcc-interface/trans.c:8823 > 8823 return gnu_result; > $45 = 0 > > so the Ada frontend resets the flag (improperly?): > > emit_check (gnu_cond=<eq_expr 0x7ffff6573938>, > gnu_expr=<plus_expr 0x7ffff6573910>, reason=10, gnat_node=2320) > at /space/rguenther/src/svn/trunk/gcc/ada/gcc-interface/trans.c:8823 > 8823 return gnu_result; > $45 = 0 > (gdb) l > 8818 > 8819 /* GNU_RESULT has side effects if and only if GNU_EXPR has: > 8820 we don't need to evaluate it just for the check. */ > 8821 TREE_SIDE_EFFECTS (gnu_result) = TREE_SIDE_EFFECTS (gnu_expr); > 8822 > 8823 return gnu_result; > 8824 } That's old code and the comment makes it quite clear why this is done though. -- Eric Botcazou