Hi,
Richard Biener <rguent...@suse.de> writes: > On Thu, 7 Sep 2023, Jiufu Guo wrote: > >> Hi, >> >> As discussed in PR111303: >> >> 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 ()". >> >> Bootstrap & regtest pass on ppc64{,le} and x86_64. >> Is this ok for trunk? > > OK, but I wonder why ->range_of_expr () doesn't return false for > undefined_p ()? While "undefined" technically means we can treat > it as nonnegative_p (or not, maybe but maybe not both), we seem to > not want to do that. So why expose it at all to ranger users > (yes, internally we in some places want to handle undefined). I guess, currently, it returns true and then lets the user check undefined_p, maybe because it tries to only return false if the type of EXPR is unsupported. Let "range_of_expr" return false for undefined_p would save checking undefined_p again when using the APIs. Committed va r14-3913. BR, Jeff (Jiufu Guo) > > Richard. > >> BR, >> Jeff (Jiufu Guo) >> >> PR middle-end/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. >> >> --- >> gcc/match.pd | 3 +++ >> gcc/testsuite/gcc.dg/pr111303.c | 11 +++++++++++ >> 2 files changed, 14 insertions(+) >> create mode 100644 gcc/testsuite/gcc.dg/pr111303.c >> >> diff --git a/gcc/match.pd b/gcc/match.pd >> index 801edb128f9..e2583ca7960 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 00000000000..eaabe55c105 >> --- /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() {} >>