re PR target/79449 (ppc builtin expansion of strncmp can cross page (4k)…

re PR target/79449 (ppc builtin expansion of strncmp can cross page (4k) boundary where it should not)

2017-02-13  Aaron Sawdey  <acsawdey@linux.vnet.ibm.com>

	PR target/79449
	* gcc.dg/strncmp-2.c: New.  Test strncmp and memcmp builtin expansion
	for reading beyond a 4k boundary.

2017-02-13  Aaron Sawdey  <acsawdey@linux.vnet.ibm.com>

	PR target/79449
	* config/rs6000/rs6000.c (expand_block_compare): Make sure runtime
	boundary crossing check and subsequent code generation agree.

From-SVN: r245392

gcc/ChangeLog

+2017-02-13  Aaron Sawdey  <acsawdey@linux.vnet.ibm.com>
+
+	PR target/79449
+	* config/rs6000/rs6000.c (expand_block_compare): Make sure runtime
+	boundary crossing check and subsequent code generation agree.
+
 2017-02-13  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* config/aarch64/aarch64.c (has_memory_op): Delete.

gcc/config/rs6000/rs6000.c

@@ -19931,14 +19931,25 @@ expand_strn_compare (rtx operands[], int no_length)
 	 cmpldi	cr7,r8,4096-16
 	 bgt	cr7,L(pagecross) */
 
+      /* Make sure that the length we use for the alignment test and
+         the subsequent code generation are in agreement so we do not
+         go past the length we tested for a 4k boundary crossing.  */
+      unsigned HOST_WIDE_INT align_test = compare_length;
+      if (align_test < 8)
+        {
+          align_test = HOST_WIDE_INT_1U << ceil_log2 (align_test);
+          base_align = align_test;
+        }
+      else
+        {
+          align_test = ROUND_UP (align_test, 8);
+          base_align = 8;
+        }
+
       if (align1 < 8)
-	expand_strncmp_align_check (strncmp_label, src1, compare_length);
+        expand_strncmp_align_check (strncmp_label, src1, align_test);
       if (align2 < 8)
-	expand_strncmp_align_check (strncmp_label, src2, compare_length);
-
-      /* After the runtime alignment checks, we can use any alignment we
-	 like as we know there is no 4k boundary crossing.  */
-      base_align = 8;
+        expand_strncmp_align_check (strncmp_label, src2, align_test);
 
       /* Now generate the following sequence:
 	 - branch to begin_compare

gcc/testsuite/ChangeLog

+2017-02-13  Aaron Sawdey  <acsawdey@linux.vnet.ibm.com>
+
+	PR target/79449
+	* gcc.dg/strncmp-2.c: New.  Test strncmp and memcmp builtin expansion
+	for reading beyond a 4k boundary.
+
 2017-02-13  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/79388

gcc/testsuite/gcc.dg/strncmp-2.c

+/* Test strncmp builtin expansion for compilation and proper execution.  */
+/* { dg-do run { target *-*-linux* *-*-gnu* } } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target ptr32plus } */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+int lib_memcmp(const void *a, const void *b, size_t n) asm("memcmp");
+int lib_strncmp(const char *a, const char *b, size_t n) asm("strncmp");
+
+static void test_driver_strncmp (void (test_strncmp)(const char *, const char *, int),
+				 void (test_memcmp)(const void *, const void *, int),
+				 size_t sz)
+{
+  long pgsz = sysconf(_SC_PAGESIZE);
+  char buf1[sz+1];
+  char *buf2 = aligned_alloc(pgsz,2*pgsz);
+  char *p2;
+  int r,i,e;
+
+  r = mprotect (buf2+pgsz,pgsz,PROT_NONE);
+  if (r < 0) abort();
+  
+  memset(buf1,'A',sz);
+  for(i=10; i>=0; i--) {
+    p2 = buf2+pgsz-sz-i;
+    memset(p2,'A',sz);
+    e = lib_strncmp(buf1,p2,sz);
+    (*test_strncmp)(buf1,p2,e);
+    e = lib_memcmp(buf1,p2,sz);
+    (*test_memcmp)(buf1,p2,e);
+  }
+}
+
+#define RUN_TEST(SZ) test_driver_strncmp (test_strncmp_ ## SZ, test_memcmp_ ## SZ, SZ);
+
+#define DEF_TEST(SZ) \
+__attribute__((noinline))						  \
+void test_strncmp_ ## SZ (const char *str1, const char *str2, int expect) \
+{									  \
+  int r;								  \
+  r = strncmp(str1,str2,SZ);						  \
+  if ( r < 0 && !(expect < 0) ) abort();				  \
+  if ( r > 0 && !(expect > 0) )	abort();				  \
+  if ( r == 0 && !(expect == 0) ) abort();				  \
+}                                                                         \
+__attribute__((noinline))						  \
+void test_memcmp_ ## SZ (const void *p1, const void *p2, int expect)      \
+{									  \
+  int r;								  \
+  r = memcmp(p1,p2,SZ);						          \
+  if ( r < 0 && !(expect < 0) ) abort();				  \
+  if ( r > 0 && !(expect > 0) )	abort();				  \
+  if ( r == 0 && !(expect == 0) ) abort();				  \
+}
+
+DEF_TEST(1)
+DEF_TEST(2)
+DEF_TEST(3)
+DEF_TEST(4)
+DEF_TEST(5)
+DEF_TEST(6)
+DEF_TEST(7)
+DEF_TEST(8)
+DEF_TEST(9)
+DEF_TEST(10)
+DEF_TEST(11)
+DEF_TEST(12)
+DEF_TEST(13)
+DEF_TEST(14)
+DEF_TEST(15)
+DEF_TEST(16)
+
+int
+main(int argc, char **argv)
+{
+  RUN_TEST(1) ;
+  RUN_TEST(2) ;
+  RUN_TEST(3) ;
+  RUN_TEST(4) ;
+  RUN_TEST(5) ;
+  RUN_TEST(6) ;
+  RUN_TEST(7) ;
+  RUN_TEST(8) ;
+  RUN_TEST(9) ;
+  RUN_TEST(10);
+  RUN_TEST(11);
+  RUN_TEST(12);
+  RUN_TEST(13);
+  RUN_TEST(14);
+  RUN_TEST(15);
+  RUN_TEST(16);
+  return 0;
+}