1 files changed, 17 insertions, 2 deletions

diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
index 241da5a1..8cdbadb9 100644
--- a/src/lj_asm_x86.h
+++ b/src/lj_asm_x86.h
@@ -2158,12 +2158,27 @@ static void asm_comp(ASMState *as, IRIns *ir, uint32_t cc)
             return;
           }  /* Otherwise handle register case as usual. */
         } else {
-          left = asm_fuseloadm(as, lref, RSET_GPR, r64);
+          left = asm_fuseloadm(as, lref,
+                               irt_isu8(ir->t) ? RSET_GPR8 : RSET_GPR, r64);
         }
         asm_guardcc(as, cc);
         if (usetest && left != RID_MRM) {
           /* Use test r,r instead of cmp r,0. */
-          emit_rr(as, irt_isu8(ir->t) ? XO_TESTb : XO_TEST, r64 + left, left);
+          x86Op xo = XO_TEST;
+          if (irt_isu8(ir->t)) {
+            lua_assert(ir->o == IR_EQ || ir->o == IR_NE);
+            xo = XO_TESTb;
+            if (!rset_test(RSET_RANGE(RID_EAX, RID_EBX+1), left)) {
+              if (LJ_64) {
+                left |= FORCE_REX;
+              } else {
+                emit_i32(as, 0xff);
+                emit_mrm(as, XO_GROUP3, XOg_TEST, left);
+                return;
+              }
+            }
+          }
+          emit_rr(as, xo, r64 + left, left);
           if (irl+1 == ir)  /* Referencing previous ins? */
             as->flagmcp = as->mcp;  /* Set flag to drop test r,r if possible. */
         } else {