diff --git a/src/lj_asm_mips.h b/src/lj_asm_mips.h
index d663aa0f..dd821c70 100644
--- a/src/lj_asm_mips.h
+++ b/src/lj_asm_mips.h
@@ -453,16 +453,13 @@ static void asm_conv(ASMState *as, IRIns *ir)
       /* y = (x ^ 0x8000000) + 2147483648.0 */
       Reg left = ra_alloc1(as, lref, RSET_GPR);
       Reg tmp = ra_scratch(as, rset_exclude(RSET_FPR, dest));
-      emit_fgh(as, irt_isfloat(ir->t) ? MIPSI_ADD_S : MIPSI_ADD_D,
-	       dest, dest, tmp);
-      emit_fg(as, irt_isfloat(ir->t) ? MIPSI_CVT_S_W : MIPSI_CVT_D_W,
-	      dest, dest);
       if (irt_isfloat(ir->t))
-	emit_lsptr(as, MIPSI_LWC1, (tmp & 31),
-		   (void *)&as->J->k32[LJ_K32_2P31], RSET_GPR);
-      else
-	emit_lsptr(as, MIPSI_LDC1, (tmp & 31),
-		   (void *)&as->J->k64[LJ_K64_2P31], RSET_GPR);
+	emit_fg(as, MIPSI_CVT_S_D, dest, dest);
+      /* Must perform arithmetic with doubles to keep the precision. */
+      emit_fgh(as, MIPSI_ADD_D, dest, dest, tmp);
+      emit_fg(as, MIPSI_CVT_D_W, dest, dest);
+      emit_lsptr(as, MIPSI_LDC1, (tmp & 31),
+		 (void *)&as->J->k64[LJ_K64_2P31], RSET_GPR);
       emit_tg(as, MIPSI_MTC1, RID_TMP, dest);
       emit_dst(as, MIPSI_XOR, RID_TMP, RID_TMP, left);
       emit_ti(as, MIPSI_LUI, RID_TMP, 0x8000);
diff --git a/src/lj_target_mips.h b/src/lj_target_mips.h
index 308dd7ce..1b061943 100644
--- a/src/lj_target_mips.h
+++ b/src/lj_target_mips.h
@@ -32,6 +32,7 @@ enum {
   RID_MAX,
   RID_ZERO = RID_R0,
   RID_TMP = RID_RA,
+  RID_GP = RID_R28,
 
   /* Calling conventions. */
   RID_RET = RID_R2,
@@ -74,10 +75,10 @@ enum {
 
 /* -- Register sets ------------------------------------------------------- */
 
-/* Make use of all registers, except ZERO, TMP, SP, SYS1, SYS2 and JGL. */
+/* Make use of all registers, except ZERO, TMP, SP, SYS1, SYS2, JGL and GP. */
 #define RSET_FIXED \
   (RID2RSET(RID_ZERO)|RID2RSET(RID_TMP)|RID2RSET(RID_SP)|\
-   RID2RSET(RID_SYS1)|RID2RSET(RID_SYS2)|RID2RSET(RID_JGL))
+   RID2RSET(RID_SYS1)|RID2RSET(RID_SYS2)|RID2RSET(RID_JGL)|RID2RSET(RID_GP))
 #define RSET_GPR	(RSET_RANGE(RID_MIN_GPR, RID_MAX_GPR) - RSET_FIXED)
 #if LJ_SOFTFP
 #define RSET_FPR	0
@@ -97,7 +98,7 @@ enum {
 
 #define RSET_SCRATCH_GPR \
   (RSET_RANGE(RID_R1, RID_R15+1)|\
-   RID2RSET(RID_R24)|RID2RSET(RID_R25)|RID2RSET(RID_R28))
+   RID2RSET(RID_R24)|RID2RSET(RID_R25))
 #if LJ_SOFTFP
 #define RSET_SCRATCH_FPR	0
 #else