[gcc r13-6624] tree-optimization/109046 - re-combine complex loads

[gcc r13-6624] tree-optimization/109046 - re-combine complex loads

[Richard Biener]

https://gcc.gnu.org/g:eb337d28c32b1b460cc85b3c00f8418ca535c77b

commit r13-6624-geb337d28c32b1b460cc85b3c00f8418ca535c77b
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Mar 7 11:04:55 2023 +0100

    tree-optimization/109046 - re-combine complex loads
    
    The following addresses PR109046 by adding an optimization to forwprop
    to combine a piecewise complex load to a complex load when there are
    no other uses of the components.  That's something useful in general and
    easier to do than avoiding the splitting in complex lowering.
    
    The testcase exercises both the manual and the complex lowering case.
    
            PR tree-optimization/109046
            * tree-ssa-forwprop.cc (pass_forwprop::execute): Combine
            piecewise complex loads.
    
            * gcc.dg/tree-ssa/forwprop-39.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/forwprop-39.c | 15 +++++++++++++
 gcc/tree-ssa-forwprop.cc                    | 33 ++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/forwprop-39.c b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-39.c
new file mode 100644
index 00000000000..eb2930e77fd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-39.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -O2 -fdump-tree-forwprop1 -fdump-tree-optimized" } */
+
+#include <complex.h>
+
+extern void push1(void *p, float _Complex x);
+void foo (void *q, float _Complex *x)
+{
+  float r = __real *x;
+  float i = __imag *x;
+  push1 (q, CMPLXF (r, i));
+}
+
+/* { dg-final { scan-tree-dump-not "COMPLEX_EXPR" "forwprop1" } } */
+/* { dg-final { scan-tree-dump-not "REALPART_EXPR" "optimized" } } */
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index 03fe0a3f6df..e34f0888954 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -3669,7 +3669,8 @@ pass_forwprop::execute (function *fun)
 	      /* Rewrite stores of a single-use complex build expression
 	         to component-wise stores.  */
 	      use_operand_p use_p;
-	      gimple *use_stmt;
+	      gimple *use_stmt, *def1, *def2;
+	      tree rhs2;
 	      if (single_imm_use (lhs, &use_p, &use_stmt)
 		  && gimple_store_p (use_stmt)
 		  && !gimple_has_volatile_ops (use_stmt)
@@ -3703,6 +3704,36 @@ pass_forwprop::execute (function *fun)
 		  release_defs (stmt);
 		  gsi_remove (&gsi, true);
 		}
+	      /* Rewrite a component-wise load of a complex to a complex
+		 load if the components are not used separately.  */
+	      else if (TREE_CODE (rhs) == SSA_NAME
+		       && has_single_use (rhs)
+		       && ((rhs2 = gimple_assign_rhs2 (stmt)), true)
+		       && TREE_CODE (rhs2) == SSA_NAME
+		       && has_single_use (rhs2)
+		       && (def1 = SSA_NAME_DEF_STMT (rhs),
+			   gimple_assign_load_p (def1))
+		       && (def2 = SSA_NAME_DEF_STMT (rhs2),
+			   gimple_assign_load_p (def2))
+		       && (gimple_vuse (def1) == gimple_vuse (def2))
+		       && !gimple_has_volatile_ops (def1)
+		       && !gimple_has_volatile_ops (def2)
+		       && gimple_assign_rhs_code (def1) == REALPART_EXPR
+		       && gimple_assign_rhs_code (def2) == IMAGPART_EXPR
+		       && operand_equal_p (TREE_OPERAND (gimple_assign_rhs1
+								 (def1), 0),
+					   TREE_OPERAND (gimple_assign_rhs1
+								 (def2), 0)))
+		{
+		  tree cl = TREE_OPERAND (gimple_assign_rhs1 (def1), 0);
+		  gimple_assign_set_rhs_from_tree (&gsi, unshare_expr (cl));
+		  gcc_assert (gsi_stmt (gsi) == stmt);
+		  gimple_set_vuse (stmt, gimple_vuse (def1));
+		  gimple_set_modified (stmt, true);
+		  gimple_stmt_iterator gsi2 = gsi_for_stmt (def1);
+		  gsi_remove (&gsi, false);
+		  gsi_insert_after (&gsi2, stmt, GSI_SAME_STMT);
+		}
 	      else
 		gsi_next (&gsi);
 	    }