With the patch this time...
Forwarded Message
Subject: [PATCH] Fix undefined behavior in h8300 backend
Date: Mon, 21 Sep 2015 11:10:04 -0600
From: Jeff Law
To: gcc-patches@gcc.gnu.org
This was found when building all configurations using the trunk
compiler. A run-of-the-mill problem with left shifting -1.
To make sure I didn't muck anything up badly, I went back to Kazu's
introduction of this pattern (2003), took his pseudo-code and turned it
into a trivial h8300 specific test.
I also verified newlib built with the new compiler. newlib never
triggers this pattern though.
I briefly pondered adding tests for the many other patterns Kazu added
in 2003 as well as generalizing andsi3_ashift_n_lower, but I just
couldn't justify that much time on the H8 port :-)
Installed on the trunk.
Jeff
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c25888a..b6527de 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2015-09-21 Jeff Law
+
+ * config/h8300/h8300.md (andsi3_ashift_n_lower): Avoid undefined
+ behavior.
+
2015-09-21 Ulrich Weigand
* config/spu/spu.c (spu_expand_insv): Avoid undefined behavior.
diff --git a/gcc/config/h8300/h8300.md b/gcc/config/h8300/h8300.md
index 4079b30..52213ac 100644
--- a/gcc/config/h8300/h8300.md
+++ b/gcc/config/h8300/h8300.md
@@ -3914,7 +3914,8 @@
(clobber (match_scratch:QI 4 "=X,&r"))]
"(TARGET_H8300H || TARGET_H8300S)
&& INTVAL (operands[2]) <= 15
-&& INTVAL (operands[3]) == ((-1 << INTVAL (operands[2])) & 0x)"
+&& UINTVAL (operands[3]) == ((HOST_WIDE_INT_M1U << INTVAL (operands[2]))
+& 0x)"
"#"
"&& reload_completed"
[(parallel [(set (match_dup 5)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c65469f..7afd523 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-09-21 Jeff Law
+
+ * gcc.target/h8300/andsi3_ashift_n_lower.c: New test.
+
2015-09-21 Ville Voutilainen
Complete the implementation of N4230, Nested namespace definition.
diff --git a/gcc/testsuite/gcc.target/h8300/andsi3_ashift_n_lower.c
b/gcc/testsuite/gcc.target/h8300/andsi3_ashift_n_lower.c
new file mode 100644
index 000..8cacc52
--- /dev/null
+++ b/gcc/testsuite/gcc.target/h8300/andsi3_ashift_n_lower.c
@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-options "-mh -O2 -fomit-frame-pointer" } */
+/* { dg-final { scan-assembler-times "extu" 1 } } */
+
+unsigned long foo(unsigned long a)
+ { return (a << 4) & 0x; }
+