From 39f5e9aded23e8b7e0e7080fc6020478b9c5b7b5 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Thu, 26 Nov 2020 10:50:23 +0100 Subject: [PATCH] match.pd: Avoid ICE with shifts [PR97979] My recent wide_int_binop changes caused ICE on this testcase. The problem is that for shift where amount has MSB set now fails to optimize into a constant (IMHO we should treat out of bounds shifts the same later), but there is a precedent for that already - e.g. division by zero fails to optimize into a constant too. I think it is better if path isolation checks for these UBs and does something the user chooses (__builtin_trap vs. __builtin_unreachable, and either a deferred warning about the UB or nothing). This patch just doesn't optimize if int_const_binop failed. 2020-11-26 Jakub Jelinek PR tree-optimization/97979 * match.pd ((X {&,^,|} C2) << C1 into (X << C1) {&,^,|} (C2 << C1)): Only optimize if int_const_binop returned non-NULL. * gcc.dg/pr97979.c: New test. * gcc.c-torture/compile/pr97979.c: New test. --- gcc/match.pd | 3 ++- gcc/testsuite/gcc.c-torture/compile/pr97979.c | 7 +++++++ gcc/testsuite/gcc.dg/pr97979.c | 13 +++++++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr97979.c create mode 100644 gcc/testsuite/gcc.dg/pr97979.c diff --git a/gcc/match.pd b/gcc/match.pd index 4d290ad3c25..f8b65154a9e 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -3119,7 +3119,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (shift (convert?:s (bit_op:s @0 INTEGER_CST@2)) INTEGER_CST@1) (if (tree_nop_conversion_p (type, TREE_TYPE (@0))) (with { tree mask = int_const_binop (shift, fold_convert (type, @2), @1); } - (bit_op (shift (convert @0) @1) { mask; })))))) + (if (mask) + (bit_op (shift (convert @0) @1) { mask; }))))))) /* ~(~X >> Y) -> X >> Y (for arithmetic shift). */ (simplify diff --git a/gcc/testsuite/gcc.c-torture/compile/pr97979.c b/gcc/testsuite/gcc.c-torture/compile/pr97979.c new file mode 100644 index 00000000000..f4f88a45adf --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/compile/pr97979.c @@ -0,0 +1,7 @@ +/* PR tree-optimization/97979 */ + +int +foo (int x) +{ + return (x & 0x123) << -3; +} diff --git a/gcc/testsuite/gcc.dg/pr97979.c b/gcc/testsuite/gcc.dg/pr97979.c new file mode 100644 index 00000000000..44aaff2ab5a --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr97979.c @@ -0,0 +1,13 @@ +/* PR tree-optimization/97979 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -fno-tree-ccp" } */ + +short a = 0; +int b = 0; + +void +foo (void) +{ + unsigned short d = b; + a = d >> -2U; /* { dg-warning "right shift count >= width of type" } */ +} -- 2.30.2