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Tiny if-conv improvement (PR tree-optimization/66142)

Message ID 20150529115230.GY10247@tucnak.redhat.com
State New
Headers show

Commit Message

Jakub Jelinek May 29, 2015, 11:52 a.m. UTC 
Hi!

On the following testcase from the PR, dce2 turns
  # .MEM_21 = PHI <.MEM_20(5), .MEM_4(D)(2)>
into
  # .MEM_21 = PHI <.MEM_21(5), .MEM_4(D)(2)>
because all writes in the loop have been dead code eliminated.
But only the phicprop2 pass much later is able to optimize this
out (by changing all .MEM_21 vuses into .MEM_4(D) vuses and removing
the virtual phi stmt).  In between those passes is if-conversion though,
and that just gives up when it sees it.  I think the test only wants
to detect conditional stores, so the above useless virtual phis
don't really pose a problem to it.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2015-05-29  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/66142
	* tree-if-conv.c (if_convertible_phi_p): Don't give up on
	virtual phis that feed themselves.

	* gcc.dg/vect/pr66142.c: New test.


	Jakub

Comments

Richard Biener May 29, 2015, 12:07 p.m. UTC | #1 
On Fri, 29 May 2015, Jakub Jelinek wrote:

> Hi!
> 
> On the following testcase from the PR, dce2 turns
>   # .MEM_21 = PHI <.MEM_20(5), .MEM_4(D)(2)>
> into
>   # .MEM_21 = PHI <.MEM_21(5), .MEM_4(D)(2)>
> because all writes in the loop have been dead code eliminated.
> But only the phicprop2 pass much later is able to optimize this
> out (by changing all .MEM_21 vuses into .MEM_4(D) vuses and removing
> the virtual phi stmt).  In between those passes is if-conversion though,
> and that just gives up when it sees it.  I think the test only wants
> to detect conditional stores, so the above useless virtual phis
> don't really pose a problem to it.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2015-05-29  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR tree-optimization/66142
> 	* tree-if-conv.c (if_convertible_phi_p): Don't give up on
> 	virtual phis that feed themselves.
> 
> 	* gcc.dg/vect/pr66142.c: New test.
> 
> --- gcc/tree-if-conv.c.jj	2015-05-21 21:16:18.000000000 +0200
> +++ gcc/tree-if-conv.c	2015-05-29 11:24:06.726448462 +0200
> @@ -594,7 +594,8 @@ if_convertible_phi_p (struct loop *loop,
>  
>        FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
>  	{
> -	  if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
> +	  if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI
> +	      && USE_STMT (use_p) != (gimple) phi)
>  	    {
>  	      if (dump_file && (dump_flags & TDF_DETAILS))
>  		fprintf (dump_file, "Difficult to handle this virtual phi.\n");
> --- gcc/testsuite/gcc.dg/vect/pr66142.c.jj	2015-05-29 11:31:21.563628051 +0200
> +++ gcc/testsuite/gcc.dg/vect/pr66142.c	2015-05-29 11:31:00.000000000 +0200
> @@ -0,0 +1,44 @@
> +/* PR middle-end/66142 */
> +/* { dg-do compile } */
> +/* { dg-additional-options "-ffast-math -fopenmp-simd" } */
> +/* { dg-additional-options "-mavx" { target avx_runtime } } */
> +
> +struct A { float x, y; };
> +struct B { struct A t, w; };
> +
> +static inline float
> +bar (const struct B *x)
> +{
> +  struct A r;
> +  float b, c, d;
> +  r.x = x->t.x;
> +  r.y = x->t.y;
> +  b = r.x * x->w.x + r.y * x->w.y;
> +  c = b + r.x * r.x + r.y * r.y;
> +  if (c > 0.0f)
> +    return c + 3.0f;
> +  return 0.0f;
> +}
> +
> +void
> +foo (float *a, float *b, float *c)
> +{
> +  int i;
> +  float z = 0.0f;
> +  float u = *a;
> +#pragma omp simd
> +  for (i = 0; i < 32; i++)
> +    {
> +      float x = b[i];
> +      float y = c[i];
> +      struct B r;
> +      r.t.x = 1.0f;
> +      r.t.y = u;
> +      r.w.x = x;
> +      r.w.y = y;
> +      z += bar (&r);
> +    }
> +  *a = z;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops in function" 1 "vect" { target vect_condition } } } */
> 
> 	Jakub
> 
>
diff mbox

Patch

--- gcc/tree-if-conv.c.jj	2015-05-21 21:16:18.000000000 +0200
+++ gcc/tree-if-conv.c	2015-05-29 11:24:06.726448462 +0200
@@ -594,7 +594,8 @@  if_convertible_phi_p (struct loop *loop,
 
       FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
 	{
-	  if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
+	  if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI
+	      && USE_STMT (use_p) != (gimple) phi)
 	    {
 	      if (dump_file && (dump_flags & TDF_DETAILS))
 		fprintf (dump_file, "Difficult to handle this virtual phi.\n");
--- gcc/testsuite/gcc.dg/vect/pr66142.c.jj	2015-05-29 11:31:21.563628051 +0200
+++ gcc/testsuite/gcc.dg/vect/pr66142.c	2015-05-29 11:31:00.000000000 +0200
@@ -0,0 +1,44 @@ 
+/* PR middle-end/66142 */
+/* { dg-do compile } */
+/* { dg-additional-options "-ffast-math -fopenmp-simd" } */
+/* { dg-additional-options "-mavx" { target avx_runtime } } */
+
+struct A { float x, y; };
+struct B { struct A t, w; };
+
+static inline float
+bar (const struct B *x)
+{
+  struct A r;
+  float b, c, d;
+  r.x = x->t.x;
+  r.y = x->t.y;
+  b = r.x * x->w.x + r.y * x->w.y;
+  c = b + r.x * r.x + r.y * r.y;
+  if (c > 0.0f)
+    return c + 3.0f;
+  return 0.0f;
+}
+
+void
+foo (float *a, float *b, float *c)
+{
+  int i;
+  float z = 0.0f;
+  float u = *a;
+#pragma omp simd
+  for (i = 0; i < 32; i++)
+    {
+      float x = b[i];
+      float y = c[i];
+      struct B r;
+      r.t.x = 1.0f;
+      r.t.y = u;
+      r.w.x = x;
+      r.w.y = y;
+      z += bar (&r);
+    }
+  *a = z;
+}
+
+/* { dg-final { scan-tree-dump-times "vectorized 1 loops in function" 1 "vect" { target vect_condition } } } */