[PATCH v2 5/5] LoongArch: Vectorized loop unrolling is disable for divf/sqrtf/rsqrtf when -mrecip is enabled.

[Jiahao Xu]

Using -mrecip generates a sequence of instructions to replace divf, sqrtf and 
rsqrtf. The number
of generated instructions is close to or exceeds the maximum issue instructions 
per cycle of the
LoongArch, so vectorized loop unrolling is not performed on them.

gcc/ChangeLog:

        * config/loongarch/loongarch.cc 
(loongarch_vector_costs::determine_suggested_unroll_factor):
        If m_has_recip is true, uf return 1.
        (loongarch_vector_costs::add_stmt_cost): Detect the use of approximate 
instruction sequence.

diff --git a/gcc/config/loongarch/loongarch.cc 
b/gcc/config/loongarch/loongarch.cc
index 2c06edcff92..0ca60e15ced 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -3974,7 +3974,9 @@ protected:
   /* Reduction factor for suggesting unroll factor.  */
   unsigned m_reduc_factor = 0;
   /* True if the loop contains an average operation. */
-  bool m_has_avg =false;
+  bool m_has_avg = false;
+  /* True if the loop uses approximation instruction sequence.  */
+  bool m_has_recip = false;
 };
 
 /* Implement TARGET_VECTORIZE_CREATE_COSTS.  */
@@ -4021,7 +4023,7 @@ loongarch_vector_costs::determine_suggested_unroll_factor 
(loop_vec_info loop_vi
 {
   class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
 
-  if (m_has_avg)
+  if (m_has_avg || m_has_recip)
     return 1;
 
   /* Don't unroll if it's specified explicitly not to be unrolled.  */
@@ -4081,6 +4083,36 @@ loongarch_vector_costs::add_stmt_cost (int count, 
vect_cost_for_stmt kind,
        }
     }
 
+  combined_fn cfn;
+  if (kind == vector_stmt
+      && stmt_info
+      && stmt_info->stmt)
+    {
+      /* Detect the use of approximate instruction sequence.  */
+      if ((TARGET_RECIP_VEC_SQRT || TARGET_RECIP_VEC_RSQRT)
+         && (cfn = gimple_call_combined_fn (stmt_info->stmt)) != CFN_LAST)
+       switch (cfn)
+         {
+         case CFN_BUILT_IN_SQRTF:
+           m_has_recip = true;
+         default:
+           break;
+         }
+      else if (TARGET_RECIP_VEC_DIV
+              && gimple_code (stmt_info->stmt) == GIMPLE_ASSIGN)
+       {
+         machine_mode mode = TYPE_MODE (vectype);
+         switch (gimple_assign_rhs_code (stmt_info->stmt))
+           {
+           case RDIV_EXPR:
+             if (GET_MODE_INNER (mode) == SFmode)
+               m_has_recip = true;
+           default:
+             break;
+           }
+       }
+    }
+
   return retval;
 }
 
-- 
2.20.1