On 29/08/18 17:43, Jakub Jelinek wrote:
On Wed, Aug 29, 2018 at 05:39:26PM +0100, Vlad Lazar wrote:
r263591 introduced the following regressions on multiple platforms:
+FAIL: c-c++-common/torture/builtin-arith-overflow-17.c -O0 execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-17.c -O2 execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-17.c -O2 -flto execution
test
+FAIL: c-c++-common/torture/builtin-arith-overflow-17.c -O2 -flto
-flto-partition=none execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-p-17.c -O0 execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-p-17.c -O2 execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-p-17.c -O2 -flto
execution test
+FAIL: c-c++-common/torture/builtin-arith-overflow-p-17.c -O2 -flto
-flto-partition=none execution test
The cause for this was that in canonicalize_comparison wi::add was used to add
a negative number. This meant
that in case of underflow the flag would not have been set. The solution is to
use wi::sub if the immediate
needs to be decremented.
The patch fixes the mentioned regressions.
Bootstrapped and regtested on aarch64-none-linux-gnu and x86_64-pc-linux-gnu.
LGTM, but ChangeLog entry is missing, can you please provide one before I
can ack it?
Sorry about that. Here's the ChangeLog:
gcc/
2018-08-29 Vlad Lazar <vlad.la...@arm.com>
* expmed.c (canonicalize_comparison): Enable underflow check.
diff --git a/gcc/expmed.c b/gcc/expmed.c
index be9f0ec9011..84f58f540ab 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -6235,7 +6235,13 @@ canonicalize_comparison (machine_mode mode, enum
rtx_code *code, rtx *imm)
wrapping around in the case of unsigned values. If any occur
cancel the optimization. */
wi::overflow_type overflow = wi::OVF_NONE;
- wide_int imm_modif = wi::add (imm_val, to_add, sgn, &overflow);
+ wide_int imm_modif;
+
+ if (to_add == 1)
+ imm_modif = wi::add (imm_val, 1, sgn, &overflow);
+ else
+ imm_modif = wi::sub (imm_val, 1, sgn, &overflow);
+
if (overflow)
return;
Jakub
