rs6000: Enable limited unrolling at -O2

In PR88760, there are a few disscussion about improve or tune unroller for
targets. And we would agree to enable unroller for small loops at O2 first.
And we could see performance improvement(~10%) for below code:
```
  subroutine foo (i, i1, block)
    integer :: i, i1
    integer :: block(9, 9, 9)
    block(i:9,1,i1) = block(i:9,1,i1) - 10
  end subroutine foo

```
This kind of code occurs a few times in exchange2 benchmark.

Similar C code:
```
  for (i = 0; i < n; i++)
    arr[i] = arr[i] - 10;
```

On powerpcle, for O2 , enable -funroll-loops and limit
PARAM_MAX_UNROLL_TIMES=2 and PARAM_MAX_UNROLLED_INSNS=20, we can see >2%
overall improvement for SPEC2017.

This patch is only for rs6000 in which we see visible performance improvement.

gcc/
2019-10-25  Jiufu Guo  <guojiufu@linux.ibm.com>	    

	PR tree-optimization/88760
	* config/rs6000/rs6000-common.c (rs6000_option_optimization_table):
	Enable -funroll-loops for -O2 and above.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Set
	PARAM_MAX_UNROLL_TIMES to 2 and PARAM_MAX_UNROLLED_INSNS to 20, and
	do not turn on web and rngreg implicitly, if the unroller is not
	explicitly enabled.
	
gcc.testsuite/
2019-10-25  Jiufu Guo  <guojiufu@linux.ibm.com>

	PR tree-optimization/88760
	* gcc.target/powerpc/small-loop-unroll.c: New test.
	* c-c++-common/tsan/thread_leak2.c: Update test.
	* gcc.dg/pr59643.c: Update test.
	* gcc.target/powerpc/loop_align.c: Update test.
	* gcc.target/powerpc/ppc-fma-1.c: Update test.
	* gcc.target/powerpc/ppc-fma-2.c: Update test.
	* gcc.target/powerpc/ppc-fma-3.c: Update test.
	* gcc.target/powerpc/ppc-fma-4.c: Update test.
	* gcc.target/powerpc/pr78604.c: Update test.

From-SVN: r277501

gcc/ChangeLog

@@ -1,3 +1,13 @@
+2019-10-25  Jiufu Guo  <guojiufu@linux.ibm.com>	    
+
+	PR tree-optimization/88760
+	* config/rs6000/rs6000-common.c (rs6000_option_optimization_table):
+	Enable -funroll-loops for -O2 and above.
+	* config/rs6000/rs6000.c (rs6000_option_override_internal): Set
+	PARAM_MAX_UNROLL_TIMES to 2 and PARAM_MAX_UNROLLED_INSNS to 20, and
+	do not turn on web and rngreg implicitly, if the unroller is not
+	explicitly enabled.
+
 2019-10-27  Jan Hubicka  <hubicka@ucw.cz>
 
 	* ipa-prop.c (ipa_propagate_indirect_call_infos): Do not remove

gcc/common/config/rs6000/rs6000-common.c

@@ -35,6 +35,7 @@ static const struct default_options rs6000_option_optimization_table[] =
     { OPT_LEVELS_ALL, OPT_fsplit_wide_types_early, NULL, 1 },
     /* Enable -fsched-pressure for first pass instruction scheduling.  */
     { OPT_LEVELS_1_PLUS, OPT_fsched_pressure, NULL, 1 },
+    { OPT_LEVELS_2_PLUS, OPT_funroll_loops, NULL, 1 },
     { OPT_LEVELS_NONE, 0, NULL, 0 }
   };
 

gcc/config/rs6000/rs6000.c

@@ -4540,6 +4540,26 @@ rs6000_option_override_internal (bool global_init_p)
 			     global_options.x_param_values,
 			     global_options_set.x_param_values);
 
+      /* unroll very small loops 2 time if no -funroll-loops.  */
+      if (!global_options_set.x_flag_unroll_loops
+	  && !global_options_set.x_flag_unroll_all_loops)
+	{
+	  maybe_set_param_value (PARAM_MAX_UNROLL_TIMES, 2,
+				 global_options.x_param_values,
+				 global_options_set.x_param_values);
+
+	  maybe_set_param_value (PARAM_MAX_UNROLLED_INSNS, 20,
+				 global_options.x_param_values,
+				 global_options_set.x_param_values);
+
+	  /* If fweb or frename-registers are not specificed in command-line,
+	     do not turn them on implicitly.  */
+	  if (!global_options_set.x_flag_web)
+	    global_options.x_flag_web = 0;
+	  if (!global_options_set.x_flag_rename_registers)
+	    global_options.x_flag_rename_registers = 0;
+	}
+
       /* If using typedef char *va_list, signal that
 	 __builtin_va_start (&ap, 0) can be optimized to
 	 ap = __builtin_next_arg (0).  */

gcc/testsuite/ChangeLog

@@ -1,3 +1,16 @@
+2019-10-25  Jiufu Guo  <guojiufu@linux.ibm.com>
+
+	PR tree-optimization/88760
+	* gcc.target/powerpc/small-loop-unroll.c: New test.
+	* c-c++-common/tsan/thread_leak2.c: Update test.
+	* gcc.dg/pr59643.c: Update test.
+	* gcc.target/powerpc/loop_align.c: Update test.
+	* gcc.target/powerpc/ppc-fma-1.c: Update test.
+	* gcc.target/powerpc/ppc-fma-2.c: Update test.
+	* gcc.target/powerpc/ppc-fma-3.c: Update test.
+	* gcc.target/powerpc/ppc-fma-4.c: Update test.
+	* gcc.target/powerpc/pr78604.c: Update test.
+
 2019-10-27  Andreas Tobler  <andreast@gcc.gnu.org>
 
 	* gcc.c-torture/execute/fprintf-2.c: Silence a Free/NetBSD libc warning.

gcc/testsuite/c-c++-common/tsan/thread_leak2.c

@@ -1,5 +1,9 @@
 /* { dg-shouldfail "tsan" } */
 
+/* { dg-additional-options "-fno-unroll-loops" { target { powerpc*-*-* } } } */
+/* -fno-unroll-loops help to avoid ThreadSanitizer reporting multi-times
+   message for pthread_create at difference calling addresses.  */
+
 #include <pthread.h>
 #include <unistd.h>
 

gcc/testsuite/gcc.dg/pr59643.c

@@ -1,6 +1,9 @@
 /* PR tree-optimization/59643 */
 /* { dg-do compile } */
 /* { dg-options "-O3 -fdump-tree-pcom-details" } */
+/* { dg-additional-options "--param max-unrolled-insns=400" { target { powerpc*-*-* } } } */
+/* Implicit threashold of max-unrolled-insn on ppc at O3 is too small for the
+   loop of this case.  */
 
 void
 foo (double *a, double *b, double *c, double d, double e, int n)

gcc/testsuite/gcc.target/powerpc/loop_align.c

@@ -1,6 +1,6 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "" { powerpc*-*-darwin* powerpc-ibm-aix* } } */
-/* { dg-options "-O2 -mdejagnu-cpu=power7 -falign-functions=16" } */
+/* { dg-options "-O2 -mdejagnu-cpu=power7 -falign-functions=16 -fno-unroll-loops" } */
 /* { dg-final { scan-assembler ".p2align 5" } } */
 
 void f(double *a, double *b, double *c, unsigned long n) {

gcc/testsuite/gcc.target/powerpc/ppc-fma-1.c

@@ -1,7 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "" { powerpc*-*-darwin* } } */
 /* { dg-require-effective-target powerpc_vsx_ok } */
-/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power7 -ffast-math" } */
+/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power7 -ffast-math -fno-unroll-loops" } */
 /* { dg-final { scan-assembler-times "xvmadd" 4 } } */
 /* { dg-final { scan-assembler-times "xsmadd\|fmadd\ " 2 } } */
 /* { dg-final { scan-assembler-times "fmadds" 2 } } */

gcc/testsuite/gcc.target/powerpc/ppc-fma-2.c

@@ -1,7 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "" { powerpc*-*-darwin* } } */
 /* { dg-require-effective-target powerpc_vsx_ok } */
-/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power7 -ffast-math -ffp-contract=off" } */
+/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power7 -ffast-math -ffp-contract=off -fno-unroll-loops" } */
 /* { dg-final { scan-assembler-times "xvmadd" 2 } } */
 /* { dg-final { scan-assembler-times "xsmadd\|fmadd\ " 1 } } */
 /* { dg-final { scan-assembler-times "fmadds" 1 } } */

gcc/testsuite/gcc.target/powerpc/ppc-fma-3.c

@@ -2,7 +2,7 @@
 /* { dg-skip-if "" { powerpc*-*-darwin* } } */
 /* { dg-require-effective-target powerpc_altivec_ok } */
 /* { dg-require-effective-target powerpc_fprs } */
-/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power6 -maltivec -ffast-math" } */
+/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power6 -maltivec -ffast-math -fno-unroll-loops" } */
 /* { dg-final { scan-assembler-times "vmaddfp" 2 } } */
 /* { dg-final { scan-assembler-times "fmadd " 2 } } */
 /* { dg-final { scan-assembler-times "fmadds" 2 } } */

gcc/testsuite/gcc.target/powerpc/ppc-fma-4.c

@@ -2,7 +2,7 @@
 /* { dg-skip-if "" { powerpc*-*-darwin* } } */
 /* { dg-require-effective-target powerpc_altivec_ok } */
 /* { dg-require-effective-target powerpc_fprs } */
-/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power6 -maltivec -ffast-math -ffp-contract=off" } */
+/* { dg-options "-O3 -ftree-vectorize -mdejagnu-cpu=power6 -maltivec -ffast-math -ffp-contract=off -fno-unroll-loops" } */
 /* { dg-final { scan-assembler-times "vmaddfp" 1 } } */
 /* { dg-final { scan-assembler-times "fmadd " 1 } } */
 /* { dg-final { scan-assembler-times "fmadds" 1 } } */

gcc/testsuite/gcc.target/powerpc/pr78604.c

@@ -1,7 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "" { powerpc*-*-darwin* } } */
 /* { dg-require-effective-target powerpc_p8vector_ok } */
-/* { dg-options "-mdejagnu-cpu=power8 -O2 -ftree-vectorize -fdump-tree-vect-details" } */
+/* { dg-options "-mdejagnu-cpu=power8 -O2 -ftree-vectorize -fdump-tree-vect-details -fno-unroll-loops" } */
 
 #ifndef SIZE
 #define SIZE 1024

gcc/testsuite/gcc.target/powerpc/small-loop-unroll.c

@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-loop2_unroll" } */
+
+void __attribute__ ((noinline)) foo(int n, int *arr)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    arr[i] = arr[i] - 10;
+}
+/* { dg-final { scan-rtl-dump-times "Unrolled loop 1 times" 1 "loop2_unroll" } } */
+/* { dg-final { scan-assembler-times {\mlwz\M} 3 } } */
+/* { dg-final { scan-assembler-times {\mstw\M} 3 } } */
+