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From: Jiu Fu Guo <guojiufu@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r14-3913] Checking undefined_p before using the vr Date: Wed, 13 Sep 2023 01:32:05 +0000 (GMT) [thread overview] Message-ID: <20230913013205.46A6B3858D3C@sourceware.org> (raw) https://gcc.gnu.org/g:8d8bc560b6ab7f3153db23ffb37157528e5b2c9a commit r14-3913-g8d8bc560b6ab7f3153db23ffb37157528e5b2c9a Author: Jiufu Guo <guojiufu@linux.ibm.com> Date: Wed Sep 6 21:38:11 2023 +0800 Checking undefined_p before using the vr For pattern "(X + C) / N": "div (plus@3 @0 INTEGER_CST@1) INTEGER_CST@2)", Even if "X" has value-range and "X + C" does not overflow, "@3" may still be undefined. Like below example: _3 = _2 + -5; if (0 != 0) goto <bb 3>; [34.00%] else goto <bb 4>; [66.00%] ;; succ: 3 ;; 4 ;; basic block 3, loop depth 0 ;; pred: 2 _5 = _3 / 5; ;; succ: 4 The whole pattern "(_2 + -5 ) / 5" is in "bb 3", but "bb 3" would be unreachable (because "if (0 != 0)" is always false). And "get_range_query (cfun)->range_of_expr (vr3, @3)" is checked in "bb 3", "range_of_expr" gets an "undefined vr3". Where "@3" is "_5". So, before using "vr3", it would be safe to check "!vr3.undefined_p ()". PR tree-optimization/111303 gcc/ChangeLog: * match.pd ((X - N * M) / N): Add undefined_p checking. ((X + N * M) / N): Likewise. ((X + C) div_rshift N): Likewise. gcc/testsuite/ChangeLog: * gcc.dg/pr111303.c: New test. Diff: --- gcc/match.pd | 3 +++ gcc/testsuite/gcc.dg/pr111303.c | 11 +++++++++++ 2 files changed, 14 insertions(+) diff --git a/gcc/match.pd b/gcc/match.pd index 39c7ea1088f2..693638f8ca03 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -975,6 +975,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) /* "X+(N*M)" doesn't overflow. */ && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr3) && get_range_query (cfun)->range_of_expr (vr4, @4) + && !vr4.undefined_p () /* "X+N*M" is not with opposite sign as "X". */ && (TYPE_UNSIGNED (type) || (vr0.nonnegative_p () && vr4.nonnegative_p ()) @@ -995,6 +996,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) /* "X - (N*M)" doesn't overflow. */ && range_op_handler (MINUS_EXPR).overflow_free_p (vr0, vr3) && get_range_query (cfun)->range_of_expr (vr4, @4) + && !vr4.undefined_p () /* "X-N*M" is not with opposite sign as "X". */ && (TYPE_UNSIGNED (type) || (vr0.nonnegative_p () && vr4.nonnegative_p ()) @@ -1025,6 +1027,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) /* "X+C" doesn't overflow. */ && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr1) && get_range_query (cfun)->range_of_expr (vr3, @3) + && !vr3.undefined_p () /* "X+C" and "X" are not of opposite sign. */ && (TYPE_UNSIGNED (type) || (vr0.nonnegative_p () && vr3.nonnegative_p ()) diff --git a/gcc/testsuite/gcc.dg/pr111303.c b/gcc/testsuite/gcc.dg/pr111303.c new file mode 100644 index 000000000000..eaabe55c105d --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr111303.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ + +/* Make sure no ICE. */ +unsigned char a; +int b(int c) { + if (c >= 5000) + return c / 5; +} +void d() { b(a - 5); } +int main() {}
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