diff options
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 47 |
1 files changed, 24 insertions, 23 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index ee9b349..fb613da 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -2649,8 +2649,7 @@ combine_comparisons (location_t loc, } /* Return nonzero if two operands (typically of the same tree node) - are necessarily equal. If either argument has side-effects this - function returns zero. FLAGS modifies behavior as follows: + are necessarily equal. FLAGS modifies behavior as follows: If OEP_ONLY_CONST is set, only return nonzero for constants. This function tests whether the operands are indistinguishable; @@ -2675,9 +2674,14 @@ combine_comparisons (location_t loc, to ensure that global memory is unchanged in between. If OEP_ADDRESS_OF is set, we are actually comparing addresses of objects, - not values of expressions. OEP_CONSTANT_ADDRESS_OF in addition to - OEP_ADDRESS_OF is used for ADDR_EXPR with TREE_CONSTANT flag set and we - further ignore any side effects on SAVE_EXPRs then. */ + not values of expressions. + + Unless OEP_MATCH_SIDE_EFFECTS is set, the function returns false on + any operand with side effect. This is unnecesarily conservative in the + case we know that arg0 and arg1 are in disjoint code paths (such as in + ?: operator). In addition OEP_MATCH_SIDE_EFFECTS is used when comparing + addresses with TREE_CONSTANT flag set so we know that &var == &var + even if var is volatile. */ int operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) @@ -2698,9 +2702,8 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST) { /* Address of INTEGER_CST is not defined; check that we did not forget - to drop the OEP_ADDRESS_OF/OEP_CONSTANT_ADDRESS_OF flags. */ - gcc_checking_assert (!(flags - & (OEP_ADDRESS_OF | OEP_CONSTANT_ADDRESS_OF))); + to drop the OEP_ADDRESS_OF flags. */ + gcc_checking_assert (!(flags & OEP_ADDRESS_OF)); return tree_int_cst_equal (arg0, arg1); } @@ -2806,7 +2809,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) they are necessarily equal as well. */ if (arg0 == arg1 && ! (flags & OEP_ONLY_CONST) && (TREE_CODE (arg0) == SAVE_EXPR - || (flags & OEP_CONSTANT_ADDRESS_OF) + || (flags & OEP_MATCH_SIDE_EFFECTS) || (! TREE_SIDE_EFFECTS (arg0) && ! TREE_SIDE_EFFECTS (arg1)))) return 1; @@ -2865,11 +2868,10 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) TREE_STRING_LENGTH (arg0))); case ADDR_EXPR: - gcc_checking_assert (!(flags - & (OEP_ADDRESS_OF | OEP_CONSTANT_ADDRESS_OF))); + gcc_checking_assert (!(flags & OEP_ADDRESS_OF)); return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), flags | OEP_ADDRESS_OF - | OEP_CONSTANT_ADDRESS_OF); + | OEP_MATCH_SIDE_EFFECTS); case CONSTRUCTOR: /* In GIMPLE empty constructors are allowed in initializers of aggregates. */ @@ -2928,7 +2930,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) /* If either of the pointer (or reference) expressions we are dereferencing contain a side effect, these cannot be equal, but their addresses can be. */ - if ((flags & OEP_CONSTANT_ADDRESS_OF) == 0 + if ((flags & OEP_MATCH_SIDE_EFFECTS) == 0 && (TREE_SIDE_EFFECTS (arg0) || TREE_SIDE_EFFECTS (arg1))) return 0; @@ -2936,11 +2938,11 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) switch (TREE_CODE (arg0)) { case INDIRECT_REF: - if (!(flags & (OEP_ADDRESS_OF | OEP_CONSTANT_ADDRESS_OF)) + if (!(flags & OEP_ADDRESS_OF) && (TYPE_ALIGN (TREE_TYPE (arg0)) != TYPE_ALIGN (TREE_TYPE (arg1)))) return 0; - flags &= ~(OEP_CONSTANT_ADDRESS_OF|OEP_ADDRESS_OF); + flags &= ~OEP_ADDRESS_OF; return OP_SAME (0); case REALPART_EXPR: @@ -2950,7 +2952,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) case TARGET_MEM_REF: case MEM_REF: - if (!(flags & (OEP_ADDRESS_OF | OEP_CONSTANT_ADDRESS_OF))) + if (!(flags & OEP_ADDRESS_OF)) { /* Require equal access sizes */ if (TYPE_SIZE (TREE_TYPE (arg0)) != TYPE_SIZE (TREE_TYPE (arg1)) @@ -2975,7 +2977,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) != TYPE_ALIGN (TREE_TYPE (arg1))) return 0; } - flags &= ~(OEP_CONSTANT_ADDRESS_OF|OEP_ADDRESS_OF); + flags &= ~OEP_ADDRESS_OF; return (OP_SAME (0) && OP_SAME (1) /* TARGET_MEM_REF require equal extra operands. */ && (TREE_CODE (arg0) != TARGET_MEM_REF @@ -2990,7 +2992,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) may have different types but same value here. */ if (!OP_SAME (0)) return 0; - flags &= ~(OEP_CONSTANT_ADDRESS_OF|OEP_ADDRESS_OF); + flags &= ~OEP_ADDRESS_OF; return ((tree_int_cst_equal (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 1)) || OP_SAME (1)) @@ -3003,13 +3005,13 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) if (!OP_SAME_WITH_NULL (0) || !OP_SAME (1)) return 0; - flags &= ~(OEP_CONSTANT_ADDRESS_OF|OEP_ADDRESS_OF); + flags &= ~OEP_ADDRESS_OF; return OP_SAME_WITH_NULL (2); case BIT_FIELD_REF: if (!OP_SAME (0)) return 0; - flags &= ~(OEP_CONSTANT_ADDRESS_OF|OEP_ADDRESS_OF); + flags &= ~OEP_ADDRESS_OF; return OP_SAME (1) && OP_SAME (2); default: @@ -3021,9 +3023,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) { case ADDR_EXPR: /* Be sure we pass right ADDRESS_OF flag. */ - gcc_checking_assert (!(flags - & (OEP_ADDRESS_OF - | OEP_CONSTANT_ADDRESS_OF))); + gcc_checking_assert (!(flags & OEP_ADDRESS_OF)); return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), flags | OEP_ADDRESS_OF); @@ -3089,6 +3089,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags) return 0; } + /* FIXME: We could skip this test for OEP_MATCH_SIDE_EFFECTS. */ { unsigned int cef = call_expr_flags (arg0); if (flags & OEP_PURE_SAME) |