From 43aada7361f4f54e0c09ae46ac46ac982182135f Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Thu, 19 Sep 2024 13:50:14 -0700 Subject: [PATCH 1/2] match: Fix `a != 0 ? a * b : 0` patterns for things that trap [PR116772] To: gcc-patches@gcc.gnu.org From: Andrew Pinski For generic, `a != 0 ? a * b : 0` would match where `b` would be an expression which trap (in the case of the testcase, it was an integer division but it could be any). This adds a new helper function, expr_no_side_effects_p which tests if there is no side effects and the expression is not trapping which might be used in other locations. Changes since v1: * v2: Add move check to helper function instead of inlining it. PR middle-end/116772 gcc/ChangeLog: * generic-match-head.cc (expr_no_side_effects_p): New function * gimple-match-head.cc (expr_no_side_effects_p): New function gcc/testsuite/ChangeLog: * gcc.dg/torture/pr116772-1.c: New test. Signed-off-by: Andrew Pinski (cherry picked from commit 6c5543d3d9c4bbcd19f0ae2b7ed7e523c978a9a8) --- gcc/generic-match-head.cc | 12 ++++++++++++ gcc/gimple-match-head.cc | 10 ++++++++++ gcc/testsuite/gcc.dg/torture/pr116772-1.c | 24 +++++++++++++++++++++++ 3 files changed, 46 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/torture/pr116772-1.c diff --git a/gcc/generic-match-head.cc b/gcc/generic-match-head.cc index 0d3f648fe8d..67ce95d3de5 100644 --- a/gcc/generic-match-head.cc +++ b/gcc/generic-match-head.cc @@ -105,6 +105,18 @@ optimize_successive_divisions_p (tree, tree) return false; } +/* Returns true if the expression T has no side effects + including not trapping. */ +static inline bool +expr_no_side_effects_p (tree t) +{ + if (TREE_SIDE_EFFECTS (t)) + return false; + if (generic_expr_could_trap_p (t)) + return false; + return true; +} + /* Return true if EXPR1 and EXPR2 have the same value, but not necessarily same type. The types can differ through nop conversions. */ diff --git a/gcc/gimple-match-head.cc b/gcc/gimple-match-head.cc index 5f8a1a1ad8e..697e69a5ba5 100644 --- a/gcc/gimple-match-head.cc +++ b/gcc/gimple-match-head.cc @@ -135,6 +135,16 @@ optimize_vectors_before_lowering_p () return !cfun || (cfun->curr_properties & PROP_gimple_lvec) == 0; } +/* Returns true if the expression T has no side effects + including not trapping. */ +static inline bool +expr_no_side_effects_p (tree t) +{ + /* For gimple, there should only be gimple val's here. */ + gcc_assert (is_gimple_val (t)); + return true; +} + /* Return true if pow(cst, x) should be optimized into exp(log(cst) * x). As a workaround for SPEC CPU2017 628.pop2_s, don't do it if arg0 is an exact integer, arg1 = phi_res +/- cst1 and phi_res = PHI diff --git a/gcc/testsuite/gcc.dg/torture/pr116772-1.c b/gcc/testsuite/gcc.dg/torture/pr116772-1.c new file mode 100644 index 00000000000..eedd0398af1 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr116772-1.c @@ -0,0 +1,24 @@ +/* { dg-do run } */ +/* PR middle-end/116772 */ +/* The division by `/b` should not + be made uncondtional. */ + +int mult0(int a,int b) __attribute__((noipa)); + +int mult0(int a,int b){ + return (b!=0 ? (a/b)*b : 0); +} + +int bit_and0(int a,int b) __attribute__((noipa)); + +int bit_and0(int a,int b){ + return (b!=0 ? (a/b)&b : 0); +} + +int main() { + if (mult0(3, 0) != 0) + __builtin_abort(); + if (bit_and0(3, 0) != 0) + __builtin_abort(); + return 0; +} -- 2.51.0 From 2f5346f25100e26624e375a5ce27bcada0b5358b Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Fri, 30 Jan 2026 15:32:39 +0100 Subject: [PATCH 2/2] middle-end/123887 - trapping conditional operand turned unconditional To: gcc-patches@gcc.gnu.org The following properly checks expr_no_side_effects_p on two patterns that turns a conditionally evaluated operand into unconditonal. PR middle-end/123887 * match.pd ((zero_one ==/!= 0) ? .. z y .. -> zero_one * z ..): Check evaluating z unconditionally has no side-effects, like trapping. * gcc.dg/torture/pr123887.c: New testcase. (cherry picked from commit c1fa15791ae458e1bd8db6842dfc021230521a65) --- gcc/match.pd | 6 ++++-- gcc/testsuite/gcc.dg/torture/pr123887.c | 14 ++++++++++++++ 2 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr123887.c diff --git a/gcc/match.pd b/gcc/match.pd index 60aa87e3d37..1d5a90e3317 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -4249,7 +4249,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (op:c @2 @1)) (if (INTEGRAL_TYPE_P (type) && TYPE_PRECISION (type) > 1 - && (INTEGRAL_TYPE_P (TREE_TYPE (@0)))) + && INTEGRAL_TYPE_P (TREE_TYPE (@0)) + && expr_no_side_effects_p (@2)) (op (mult (convert:type @0) @2) @1)))) /* (zero_one != 0) ? z y : y -> ((typeof(y))zero_one * z) y */ @@ -4261,7 +4262,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) @1) (if (INTEGRAL_TYPE_P (type) && TYPE_PRECISION (type) > 1 - && (INTEGRAL_TYPE_P (TREE_TYPE (@0)))) + && INTEGRAL_TYPE_P (TREE_TYPE (@0)) + && expr_no_side_effects_p (@2)) (op (mult (convert:type @0) @2) @1)))) /* ?: Value replacement. */ diff --git a/gcc/testsuite/gcc.dg/torture/pr123887.c b/gcc/testsuite/gcc.dg/torture/pr123887.c new file mode 100644 index 00000000000..c2a9659c5b5 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr123887.c @@ -0,0 +1,14 @@ +/* { dg-do run } */ + +typedef struct { + unsigned s; +} struct_t; + +struct_t *p; +_Bool cond; +int v = 1; +int main() +{ + int u = 1 + (cond ? p->s : 0); + return u - v; +} -- 2.51.0