Re: [PATCH][tree-ssa-math-opts] Expand pow (x, CONST) using square roots when possible

[Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>]

On 18/05/15 11:32, Richard Biener wrote:
> On Wed, May 13, 2015 at 5:33 PM, Kyrill Tkachov
> <kyrylo.tkachov@foss.arm.com> wrote:
> > Hi Richard,
> >
> > On 13/05/15 12:27, Richard Biener wrote:
> > > > > I notice that we don't have a testuite check that the target has
> > > > > > > a hw sqrt instructions. Would you like me to add one? Or can I make
> > > > > > > the testcase aarch64-specific?
> > > Would be great to have a testsuite check for this.
> > I've committed the patch with r223167.
> >
> > The attached patch adds a testsuite check for hardware sqrt instructions.
> > In this version I've included arm (on the condition that vfp is possible),
> > aarch64, x86_64 and powerpc with vsx.
> > Is this definition ok?
> >
> > I'm particularly not familiar with the powerpc architectures.
> >
> > With this check in place, I've migrated the pow synthesis test from
> > gcc.target/aarch64 to gcc.dg.
> >
> > This test passes on arm-none-eabi, aarch64-none-elf and x86_64-linux.
> >
> > Ok?
> Ok.

Thanks.
However, after some discussion on IRC I'd prefer to rename the testsuite check
to sqrt_insn so as not to give the impression that it is a runtime hardware check.

Also, this version adds an entry in sourcebuild.texi.

I'll commit this version in 24 hours unless someone objects.
Test still passes on arm, x86_64 and aarch64.

Cheers,
Kyrill

2015-05-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * lib/target-supports.exp (check_effective_target_sqrt_insn): New check.
     * gcc.dg/pow-sqrt-synth-1.c: New test.
     * gcc.target/aarch64/pow-sqrt-synth-1.c: Delete.

2015-05-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * doc/sourcebuild.texi (7.2.3.9 Other hardware attributes):
    Document sqrt_insn.
> Thanks,
> Richard.
>
> > 2015-05-13  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> >
> >      * lib/target-supports.exp (check_effective_target_hw_sqrt): New check.
> >      * gcc.dg/pow-sqrt-synth-1.c: New test.
> >      * gcc.target/aarch64/pow-sqrt-synth-1.c: Delete.

commit e35362535c9888daf00d1430e2d3a932d7ece228
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Wed May 13 16:08:03 2015 +0100

    Add testsuite check for hw sqrt. Add generic test for pow sqrt synthesis

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index c6ef40e..abe0779 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -1695,6 +1695,9 @@ Target supports FPU instructions.
 @item non_strict_align
 Target does not require strict alignment.
 
+@item sqrt_insn
+Target has a square root instruction that the compiler can generate.
+
 @item sse
 Target supports compiling @code{sse} instructions.
 
diff --git a/gcc/testsuite/gcc.dg/pow-sqrt-synth-1.c b/gcc/testsuite/gcc.dg/pow-sqrt-synth-1.c
new file mode 100644
index 0000000..d55b626
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pow-sqrt-synth-1.c
@@ -0,0 +1,38 @@
+/* { dg-do compile { target sqrt_insn } } */
+/* { dg-options "-fdump-tree-sincos -Ofast --param max-pow-sqrt-depth=8" } */
+/* { dg-additional-options "-mfloat-abi=softfp -mfpu=neon-vfpv4" { target arm*-*-* } } */
+
+double
+foo (double a)
+{
+  return __builtin_pow (a, -5.875);
+}
+
+double
+foof (double a)
+{
+  return __builtin_pow (a, 0.75f);
+}
+
+double
+bar (double a)
+{
+  return __builtin_pow (a, 1.0 + 0.00390625);
+}
+
+double
+baz (double a)
+{
+  return __builtin_pow (a, -1.25) + __builtin_pow (a, 5.75) - __builtin_pow (a, 3.375);
+}
+
+#define N 256
+void
+vecfoo (double *a)
+{
+  for (int i = 0; i < N; i++)
+    a[i] = __builtin_pow (a[i], 1.25);
+}
+
+/* { dg-final { scan-tree-dump-times "synthesizing" 7 "sincos" } } */
+/* { dg-final { cleanup-tree-dump "sincos" } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/pow-sqrt-synth-1.c b/gcc/testsuite/gcc.target/aarch64/pow-sqrt-synth-1.c
deleted file mode 100644
index 52514fb..0000000
--- a/gcc/testsuite/gcc.target/aarch64/pow-sqrt-synth-1.c
+++ /dev/null
@@ -1,38 +0,0 @@
-/* { dg-do compile } */
-/* { dg-options "-fdump-tree-sincos -Ofast --param max-pow-sqrt-depth=8" } */
-
-
-double
-foo (double a)
-{
-  return __builtin_pow (a, -5.875);
-}
-
-double
-foof (double a)
-{
-  return __builtin_pow (a, 0.75f);
-}
-
-double
-bar (double a)
-{
-  return __builtin_pow (a, 1.0 + 0.00390625);
-}
-
-double
-baz (double a)
-{
-  return __builtin_pow (a, -1.25) + __builtin_pow (a, 5.75) - __builtin_pow (a, 3.375);
-}
-
-#define N 256
-void
-vecfoo (double *a)
-{
-  for (int i = 0; i < N; i++)
-    a[i] = __builtin_pow (a[i], 1.25);
-}
-
-/* { dg-final { scan-tree-dump-times "synthesizing" 7 "sincos" } } */
-/* { dg-final { cleanup-tree-dump "sincos" } } */
\ No newline at end of file
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 3728927..e3c4416 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -4668,6 +4668,27 @@ proc check_effective_target_vect_call_copysignf { } {
     return $et_vect_call_copysignf_saved
 }
 
+# Return 1 if the target supports hardware square root instructions.
+
+proc check_effective_target_sqrt_insn { } {
+    global et_sqrt_insn_saved
+
+    if [info exists et_sqrt_insn_saved] {
+	verbose "check_effective_target_hw_sqrt: using cached result" 2
+    } else {
+	set et_sqrt_insn_saved 0
+	if { [istarget x86_64-*-*]
+	     || [istarget powerpc*-*-*]
+	     || [istarget aarch64*-*-*]
+	     || ([istarget arm*-*-*] && [check_effective_target_arm_vfp_ok]) } {
+	   set et_sqrt_insn_saved 1
+	}
+    }
+
+    verbose "check_effective_target_hw_sqrt: returning et_sqrt_insn_saved" 2
+    return $et_sqrt_insn_saved
+}
+
 # Return 1 if the target supports vector sqrtf calls.
 
 proc check_effective_target_vect_call_sqrtf { } {