[RFC] Use which_alternative in preparation-statements of define_insn_and_split

[Jiangning Liu]

Hi,

I find which_alternative can't really be used in preparation-statements of
define_insn_and_split, so can this be fixed like below?

For example, I want to use which_alternative in the pattern below,

(define_insn_and_split "*thumb2_movsicc_insn"
  [(set (match_operand:SI 0 "s_register_operand" "=r,r,r,r,r,r,r,r")
        (if_then_else:SI
         (match_operator 3 "arm_comparison_operator"
          [(match_operand 4 "cc_register" "") (const_int 0)])
         (match_operand:SI 1 "arm_not_operand" "0,0,rI,K,rI,rI,K,K")
         (match_operand:SI 2 "arm_not_operand" "rI,K,0,0,rI,K,rI,K")))]
  "TARGET_THUMB2"
  "@
   it\\t%D3\;mov%D3\\t%0, %2
   it\\t%D3\;mvn%D3\\t%0, #%B2
   it\\t%d3\;mov%d3\\t%0, %1
   it\\t%d3\;mvn%d3\\t%0, #%B1
   ite\\t%d3\;mov%d3\\t%0, %1\;mov%D3\\t%0, %2
   ite\\t%d3\;mov%d3\\t%0, %1\;mvn%D3\\t%0, #%B2
   ite\\t%d3\;mvn%d3\\t%0, #%B1\;mov%D3\\t%0, %2
   ite\\t%d3\;mvn%d3\\t%0, #%B1\;mvn%D3\\t%0, #%B2"
  "&& reload_completed"
  [(cond_exec (match_dup 5)
              (set (match_dup 0) (match_dup 6)))]
  "
  {
    if (which_alternative >= 2 && which_alternative < 4)
      {
        ...
      }
    else if (which_alternative >= 4)
      {
        ...
      }
  }"
  [(set_attr "length" "6,6,6,6,10,10,10,10")
   (set_attr "conds" "use")]
)

Thanks,
-Jiangning

Patch:

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index c94e743..df6a3df
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -3502,6 +3502,10 @@ try_split (rtx pat, rtx trial, int last)
     split_branch_probability = INTVAL (XEXP (note, 0));
   probability = split_branch_probability;

+  extract_insn (trial);
+  if (!constrain_operands (reload_completed))
+    return trial;
+
   seq = split_insns (pat, trial);

   split_branch_probability = -1;