Re: [PATCH v2 34/35] target/alpha: Use TCG_COND_TSTNE for gen_fold_mzero

[Philippe Mathieu-Daudé]

On 28/10/23 21:45, Richard Henderson wrote:

Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
  target/alpha/translate.c | 49 +++++++++++++++++++---------------------
  1 file changed, 23 insertions(+), 26 deletions(-)

diff --git a/target/alpha/translate.c b/target/alpha/translate.c
index c7daf46de7..c68c2bcd21 100644
--- a/target/alpha/translate.c
+++ b/target/alpha/translate.c
@@ -490,56 +490,53 @@ static DisasJumpType gen_bcond(DisasContext *ctx, TCGCond 
cond, int ra,

/* Fold -0.0 for comparison with COND. */ -static void gen_fold_mzero(TCGCond cond, TCGv dest, TCGv src)

+static TCGv_i64 gen_fold_mzero(TCGCond *pcond, uint64_t *pimm, TCGv_i64 src)
  {
-    uint64_t mzero = 1ull << 63;
+    TCGv_i64 tmp;

- switch (cond) {

+    *pimm = 0;
+    switch (*pcond) {
      case TCG_COND_LE:
      case TCG_COND_GT:
          /* For <= or >, the -0.0 value directly compares the way we want.  */
-        tcg_gen_mov_i64(dest, src);
-        break;
+        return src;

case TCG_COND_EQ:

      case TCG_COND_NE:
-        /* For == or !=, we can simply mask off the sign bit and compare.  */
-        tcg_gen_andi_i64(dest, src, mzero - 1);
-        break;
+        /* For == or !=, we can compare without the sign bit. */

+        *pcond = *pcond == TCG_COND_EQ ? TCG_COND_TSTEQ : TCG_COND_TSTNE;

OK, $subject is only this line, the rest is purely refactoring.

Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>

+        *pimm = INT64_MAX;
+        return src;

case TCG_COND_GE:

      case TCG_COND_LT:
          /* For >= or <, map -0.0 to +0.0. */
-        tcg_gen_movcond_i64(TCG_COND_NE, dest, src, tcg_constant_i64(mzero),
-                            src, tcg_constant_i64(0));
-        break;
+        tmp = tcg_temp_new_i64();
+        tcg_gen_movcond_i64(TCG_COND_EQ, tmp,
+                            src, tcg_constant_i64(INT64_MIN),
+                            tcg_constant_i64(0), src);
+        return tmp;

default:

-        abort();
+        g_assert_not_reached();
      }
  }