tcg: Optimize spills of constants

While we can store constants via constrants on INDEX_op_st_i32 et al,
we weren't able to spill constants to backing store.

Add a new backend interface, tcg_out_sti, which may store the constant
(and is allowed to fail).  Rearrange the temp_* helpers so that we only
attempt to directly store a constant when the temp is becoming dead/free.

Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c
index 1447f7c216..5ac0091906 100644
--- a/tcg/aarch64/tcg-target.inc.c
+++ b/tcg/aarch64/tcg-target.inc.c
@@ -716,6 +716,16 @@ static inline void tcg_out_st(TCGContext *s, TCGType type, TCGReg arg,
                  arg, arg1, arg2);
 }
 
+static inline bool tcg_out_sti(TCGContext *s, TCGType type, TCGArg val,
+                               TCGReg base, intptr_t ofs)
+{
+    if (val == 0) {
+        tcg_out_st(s, type, TCG_REG_XZR, base, ofs);
+        return true;
+    }
+    return false;
+}
+
 static inline void tcg_out_bfm(TCGContext *s, TCGType ext, TCGReg rd,
                                TCGReg rn, unsigned int a, unsigned int b)
 {