Combine i8/u8 XLOAD with BAND+comparison into test byte mrm, imm8.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/lj_asm.c b/src/lj_asm.c
index bda86fc4..cc2ae597 100644
--- a/src/lj_asm.c
+++ b/src/lj_asm.c
@@ -2945,8 +2945,28 @@ static void asm_comp_(ASMState *as, IRIns *ir, int cc)
         if (!asm_isk32(as, irl->op2, &imm)) {
           left = ra_alloc1(as, irl->op2, allow);
           rset_clear(allow, left);
+        } else {  /* Try to Fuse IRT_I8/IRT_U8 loads, too. See below. */
+          IRIns *irll = IR(irl->op1);
+          if (opisfusableload((IROp)irll->o) &&
+              (irt_isi8(irll->t) || irt_isu8(irll->t))) {
+            IRType1 origt = irll->t;  /* Temporarily flip types. */
+            irll->t.irt = (irll->t.irt & ~IRT_TYPE) | IRT_INT;
+            as->curins--;  /* Skip to BAND to avoid failing in noconflict(). */
+            right = asm_fuseload(as, irl->op1, RSET_GPR);
+            as->curins++;
+            irll->t = origt;
+            if (right != RID_MRM) goto test_nofuse;
+            /* Fusion succeeded, emit test byte mrm, imm8. */
+            asm_guardcc(as, cc);
+            emit_i8(as, (imm & 0xff));
+            emit_mrm(as, XO_GROUP3b, XOg_TEST, RID_MRM);
+            return;
+          }
         }
+        as->curins--;  /* Skip to BAND to avoid failing in noconflict(). */
         right = asm_fuseload(as, irl->op1, allow);
+        as->curins++;  /* Undo the above. */
+      test_nofuse:
         asm_guardcc(as, cc);
         if (ra_noreg(left)) {
           emit_i32(as, imm);