gimple-isel: Fold x CMP y ? -1 : 0 to x CMP y [PR97872]

gcc/
2020-12-08  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	PR target/97872
	* gimple-isel.cc (gimple_expand_vec_cond_expr): Try to fold
	x CMP y ? -1 : 0 to x CMP y.

gcc/testsuite/
2020-12-08  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	PR target/97872
	* gcc.target/arm/pr97872.c: New test.

diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
index d79c212..1ab75e7 100644 (file)
--- a/gcc/gimple-isel.cc
+++ b/gcc/gimple-isel.cc
@@ -184,6 +184,20 @@ gimple_expand_vec_cond_expr (gimple_stmt_iterator *gsi,
 
          tree op0_type = TREE_TYPE (op0);
          tree op0a_type = TREE_TYPE (op0a);
+
+         /* Try to fold x CMP y ? -1 : 0 to x CMP y.  */
+
+         if (integer_minus_onep (op1)
+             && integer_zerop (op2)
+             && TYPE_MODE (TREE_TYPE (lhs)) == TYPE_MODE (TREE_TYPE (op0))
+             && expand_vec_cmp_expr_p (op0a_type, op0_type, tcode))
+           {
+             tree conv_op = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (lhs), op0);
+             gassign *new_stmt = gimple_build_assign (lhs, conv_op);
+             gsi_replace (gsi, new_stmt, true);
+             return new_stmt;
+           }
+
          if (used_vec_cond_exprs >= 2
              && (get_vcond_mask_icode (mode, TYPE_MODE (op0_type))
                  != CODE_FOR_nothing)

diff --git a/gcc/testsuite/gcc.target/arm/pr97872.c b/gcc/testsuite/gcc.target/arm/pr97872.c
new file mode 100644 (file)
index 0000000..eeb4dd9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr97872.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_neon_ok } */
+/* { dg-options "-O3" } */
+/* { dg-add-options arm_neon } */
+
+#include <arm_neon.h>
+
+uint8x8_t f1(int8x8_t a, int8x8_t b) {
+  return a < b;
+}
+
+/* { dg-final { scan-assembler-not "vbsl" } } */