Eliminate the use of i_fetch in arithmetic instructions

The i_fetch instruction fetches two operands and places them
in the tmp_arg1 and tmp_arg2 variables. The next instruction
(such as i_plus) does not have to handle different types of
operands, but can get get them simply from the tmp_arg*
variables. Thus, i_fetch was introduced as a way to temper
a potentail combinatorial explosion.

Unfortunately, clang will generate terrible code because of
the tmp_arg1 and tmp_arg2 variables being live across multiple
instructions. Note that Clang has no way to predict the control
flow from one instruction to another. Clang must assume that
any instruction can jump to any other instruction. Somehow GCC
manages to cope with this situation much better.

Therefore, to improve the quality of the code generated by clang, we
must eliminate all uses of the tmp_arg1 and tmp_arg2 variables. This
commit eliminates the use of i_fetch in combination with the
arithmetic and logical instructions.

While we are touching the code for the bsr and bsl instructions,
also move the tmp_big[] array from top scope of process main into
the block that encloses the bsr and bsl instructions.

1 files changed, 140 insertions, 179 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index e5179830de..82cc030878 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -1145,7 +1145,6 @@ void process_main(void)
      */
     register Eterm tmp_arg1 REG_tmp_arg1 = NIL;
     register Eterm tmp_arg2 REG_tmp_arg2 = NIL;
-    Eterm tmp_big[2];
 
     /*
      * X registers and floating point registers are located in
@@ -1158,8 +1157,6 @@ void process_main(void)
      */
     int neg_o_reds = 0;
 
-    Eterm (*arith_func)(Process* p, Eterm* reg, Uint live);
-
 #ifdef ERTS_OPCODE_COUNTER_SUPPORT
     static void* counting_opcodes[] = { DEFINE_COUNTING_OPCODES };
 #else
@@ -1307,9 +1304,6 @@ void process_main(void)
 #endif
 #include "beam_hot.h"
 
-#define STORE_ARITH_RESULT(res) StoreBifResult(2, (res));
-#define ARITH_FUNC(name) erts_gc_##name
-
 	{
 	    Eterm increment_reg_val;
 	    Eterm increment_val;
@@ -1349,81 +1343,71 @@ void process_main(void)
 	    goto find_func_info;
 	}
 
-#define DO_BIG_ARITH(Func,Arg1,Arg2)     \
-    do {                                 \
-        Uint live = Arg(1);              \
-        SWAPOUT;                         \
-        reg[live] = (Arg1);              \
-        reg[live+1] = (Arg2);            \
-        result = (Func)(c_p, reg, live); \
-        SWAPIN;                          \
-        ERTS_HOLE_CHECK(c_p);            \
-        if (is_value(result)) {          \
-            StoreBifResult(4,result);    \
-        }                                \
-        goto lb_Cl_error;                \
-    } while(0)
+#define DO_OUTLINED_ARITH_2(name, Op1, Op2)	\
+ do {						\
+     Eterm result;				\
+     Uint live = Arg(1);			\
+						\
+     SWAPOUT;					\
+     reg[live] = Op1;				\
+     reg[live+1] = Op2;				\
+     result = erts_gc_##name(c_p, reg, live);	\
+     SWAPIN;					\
+     ERTS_HOLE_CHECK(c_p);			\
+     if (is_value(result)) {			\
+	 StoreBifResult(4, result);		\
+     }						\
+     goto lb_Cl_error;				\
+ } while (0)
 
- OpCase(i_plus_jIxxd):
  {
+     Eterm PlusOp1, PlusOp2;
      Eterm result;
 
-     if (is_both_small(xb(Arg(2)), xb(Arg(3)))) {
-	 Sint i = signed_val(xb(Arg(2))) + signed_val(xb(Arg(3)));
-	 ASSERT(MY_IS_SSMALL(i) == IS_SSMALL(i));
-	 if (MY_IS_SSMALL(i)) {
-	     result = make_small(i);
-             StoreBifResult(4, result);
-	 }
-     }
-     DO_BIG_ARITH(ARITH_FUNC(mixed_plus), xb(Arg(2)), xb(Arg(3)));
- }
+ OpCase(i_plus_jIxxd):
+     PlusOp1 = xb(Arg(2));
+     PlusOp2 = xb(Arg(3));
+     goto do_plus;
 
- OpCase(i_plus_jId):
- {
-     Eterm result;
+ OpCase(i_plus_jIssd):
+     GetArg2(2, PlusOp1, PlusOp2);
+     goto do_plus;
 
-     if (is_both_small(tmp_arg1, tmp_arg2)) {
-	 Sint i = signed_val(tmp_arg1) + signed_val(tmp_arg2);
+ do_plus:
+     if (is_both_small(PlusOp1, PlusOp2)) {
+	 Sint i = signed_val(PlusOp1) + signed_val(PlusOp2);
 	 ASSERT(MY_IS_SSMALL(i) == IS_SSMALL(i));
 	 if (MY_IS_SSMALL(i)) {
 	     result = make_small(i);
-	     STORE_ARITH_RESULT(result);
+             StoreBifResult(4, result);
 	 }
      }
-     arith_func = ARITH_FUNC(mixed_plus);
-     goto do_big_arith2;
+     DO_OUTLINED_ARITH_2(mixed_plus, PlusOp1, PlusOp2);
  }
 
- OpCase(i_minus_jIxxd):
  {
+     Eterm MinusOp1, MinusOp2;
      Eterm result;
 
-     if (is_both_small(xb(Arg(2)), xb(Arg(3)))) {
-	 Sint i = signed_val(xb(Arg(2))) - signed_val(xb(Arg(3)));
-	 ASSERT(MY_IS_SSMALL(i) == IS_SSMALL(i));
-	 if (MY_IS_SSMALL(i)) {
-	     result = make_small(i);
-             StoreBifResult(4, result);
-	 }
-     }
-     DO_BIG_ARITH(ARITH_FUNC(mixed_minus), xb(Arg(2)), xb(Arg(3)));
- }
+ OpCase(i_minus_jIxxd):
+     MinusOp1 = xb(Arg(2));
+     MinusOp2 = xb(Arg(3));
+     goto do_minus;
 
- OpCase(i_minus_jId):
- {
-     Eterm result;
+ OpCase(i_minus_jIssd):
+     GetArg2(2, MinusOp1, MinusOp2);
+     goto do_minus;
 
-     if (is_both_small(tmp_arg1, tmp_arg2)) {
-	 Sint i = signed_val(tmp_arg1) - signed_val(tmp_arg2);
+ do_minus:
+     if (is_both_small(MinusOp1, MinusOp2)) {
+	 Sint i = signed_val(MinusOp1) - signed_val(MinusOp2);
 	 ASSERT(MY_IS_SSMALL(i) == IS_SSMALL(i));
 	 if (MY_IS_SSMALL(i)) {
 	     result = make_small(i);
-	     STORE_ARITH_RESULT(result);
+             StoreBifResult(4, result);
 	 }
      }
-     arith_func = ARITH_FUNC(mixed_minus);
-     goto do_big_arith2;
+     DO_OUTLINED_ARITH_2(mixed_minus, MinusOp1, MinusOp2);
  }
 
  OpCase(i_is_lt_f):
@@ -2767,109 +2751,81 @@ do {						\
   * Arithmetic operations.
   */
 
- OpCase(i_times_jId):
+ OpCase(i_times_jIssd):
  {
-     arith_func = ARITH_FUNC(mixed_times);
-     goto do_big_arith2;
+     Eterm Op1, Op2;
+     GetArg2(2, Op1, Op2);
+     DO_OUTLINED_ARITH_2(mixed_times, Op1, Op2);
  }
 
- OpCase(i_m_div_jId):
+ OpCase(i_m_div_jIssd):
  {
-     arith_func = ARITH_FUNC(mixed_div);
-     goto do_big_arith2;
+     Eterm Op1, Op2;
+     GetArg2(2, Op1, Op2);
+     DO_OUTLINED_ARITH_2(mixed_div, Op1, Op2);
  }
 
- OpCase(i_int_div_jId):
+ OpCase(i_int_div_jIssd):
  {
-     Eterm result;
+     Eterm Op1, Op2;
 
-     if (tmp_arg2 == SMALL_ZERO) {
+     GetArg2(2, Op1, Op2);
+     if (Op2 == SMALL_ZERO) {
 	 goto badarith;
-     } else if (is_both_small(tmp_arg1, tmp_arg2)) {
-	 Sint ires = signed_val(tmp_arg1) / signed_val(tmp_arg2);
+     } else if (is_both_small(Op1, Op2)) {
+	 Sint ires = signed_val(Op1) / signed_val(Op2);
 	 if (MY_IS_SSMALL(ires)) {
-	     result = make_small(ires);
-	     STORE_ARITH_RESULT(result);
+	     Eterm result = make_small(ires);
+	     StoreBifResult(4, result);
 	 }
      }
-     arith_func = ARITH_FUNC(int_div);
-     goto do_big_arith2;
+     DO_OUTLINED_ARITH_2(int_div, Op1, Op2);
  }
 
- OpCase(i_rem_jIxxd):
  {
-     Eterm result;
+     Eterm RemOp1, RemOp2;
 
-     if (xb(Arg(3)) == SMALL_ZERO) {
-	 goto badarith;
-     } else if (is_both_small(xb(Arg(2)), xb(Arg(3)))) {
-	 result = make_small(signed_val(xb(Arg(2))) % signed_val(xb(Arg(3))));
+ OpCase(i_rem_jIxxd):
+     RemOp1 = xb(Arg(2));
+     RemOp2 = xb(Arg(3));
+     goto do_rem;
+
+ OpCase(i_rem_jIssd):
+     GetArg2(2, RemOp1, RemOp2);
+     goto do_rem;
+
+ do_rem:
+     if (RemOp2 == SMALL_ZERO) {
+         goto badarith;
+     } else if (is_both_small(RemOp1, RemOp2)) {
+         Eterm result = make_small(signed_val(RemOp1) % signed_val(RemOp2));
          StoreBifResult(4, result);
+     } else {
+	 DO_OUTLINED_ARITH_2(int_rem, RemOp1, RemOp2);
      }
-     DO_BIG_ARITH(ARITH_FUNC(int_rem),xb(Arg(2)),xb(Arg(3)));
  }
 
- OpCase(i_rem_jId):
  {
-     Eterm result;
-
-     if (tmp_arg2 == SMALL_ZERO) {
-	 goto badarith;
-     } else if (is_both_small(tmp_arg1, tmp_arg2)) {
-	 result = make_small(signed_val(tmp_arg1) % signed_val(tmp_arg2));
-	 STORE_ARITH_RESULT(result);
-     } else {
-	 arith_func = ARITH_FUNC(int_rem);
-	 goto do_big_arith2;
-     }
- }
+     Eterm BandOp1, BandOp2;
 
  OpCase(i_band_jIxcd):
- {
-     Eterm result;
+     BandOp1 = xb(Arg(2));
+     BandOp2 = Arg(3);
+     goto do_band;
+
+ OpCase(i_band_jIssd):
+     GetArg2(2, BandOp1, BandOp2);
+     goto do_band;
 
-     if (is_both_small(xb(Arg(2)), Arg(3))) {
+ do_band:
+     if (is_both_small(BandOp1, BandOp2)) {
          /*
           * No need to untag -- TAG & TAG == TAG.
           */
-         result = xb(Arg(2)) & Arg(3);
+         Eterm result = BandOp1 & BandOp2;
          StoreBifResult(4, result);
      }
-     DO_BIG_ARITH(ARITH_FUNC(band),xb(Arg(2)),Arg(3));
- }
-
- OpCase(i_band_jId):
- {
-     Eterm result;
-
-     if (is_both_small(tmp_arg1, tmp_arg2)) {
-	 /*
-	  * No need to untag -- TAG & TAG == TAG.
-	  */
-	 result = tmp_arg1 & tmp_arg2;
-	 STORE_ARITH_RESULT(result);
-     }
-     arith_func = ARITH_FUNC(band);
-     goto do_big_arith2;
- }
-
-#undef DO_BIG_ARITH
-
- do_big_arith2:
- {
-     Eterm result;
-     Uint live = Arg(1);
-
-     SWAPOUT;
-     reg[live] = tmp_arg1;
-     reg[live+1] = tmp_arg2;
-     result = arith_func(c_p, reg, live);
-     SWAPIN;
-     ERTS_HOLE_CHECK(c_p);
-     if (is_value(result)) {
-	 STORE_ARITH_RESULT(result);
-     }
-     goto lb_Cl_error;
+     DO_OUTLINED_ARITH_2(band, BandOp1, BandOp2);
  }
 
  /*
@@ -2890,97 +2846,102 @@ do {						\
      goto find_func_info;
  }
 
- OpCase(i_bor_jId):
+ OpCase(i_bor_jIssd):
  {
-     Eterm result;
+     Eterm Op1, Op2;
 
-     if (is_both_small(tmp_arg1, tmp_arg2)) {
+     GetArg2(2, Op1, Op2);
+     if (is_both_small(Op1, Op2)) {
 	 /*
 	  * No need to untag -- TAG | TAG == TAG.
 	  */
-	 result = tmp_arg1 | tmp_arg2;
-	 STORE_ARITH_RESULT(result);
+	 Eterm result = Op1 | Op2;
+	 StoreBifResult(4, result);
      }
-     arith_func = ARITH_FUNC(bor);
-     goto do_big_arith2;
+     DO_OUTLINED_ARITH_2(bor, Op1, Op2);
  }
 
- OpCase(i_bxor_jId):
+ OpCase(i_bxor_jIssd):
  {
-     Eterm result;
+     Eterm Op1, Op2;
 
-     if (is_both_small(tmp_arg1, tmp_arg2)) {
+     GetArg2(2, Op1, Op2);
+     if (is_both_small(Op1, Op2)) {
 	 /*
 	  * We could extract the tag from one argument, but a tag extraction
 	  * could mean a shift.  Therefore, play it safe here.
 	  */
-	 result = make_small(signed_val(tmp_arg1) ^ signed_val(tmp_arg2));
-	 STORE_ARITH_RESULT(result);
+	 Eterm result = make_small(signed_val(Op1) ^ signed_val(Op2));
+	 StoreBifResult(4, result);
      }
-     arith_func = ARITH_FUNC(bxor);
-     goto do_big_arith2;
+     DO_OUTLINED_ARITH_2(bxor, Op1, Op2);
  }
 
  {
+     Eterm Op1, Op2;
      Sint i;
      Sint ires;
      Eterm* bigp;
+     Eterm tmp_big[2];
 
-     OpCase(i_bsr_jId):
-	 if (is_small(tmp_arg2)) {
-	     i = -signed_val(tmp_arg2);
-	     if (is_small(tmp_arg1)) {
+     OpCase(i_bsr_jIssd):
+         GetArg2(2, Op1, Op2);
+	 if (is_small(Op2)) {
+	     i = -signed_val(Op2);
+	     if (is_small(Op1)) {
 		 goto small_shift;
-	     } else if (is_big(tmp_arg1)) {
+	     } else if (is_big(Op1)) {
 		 if (i == 0) {
-		     StoreBifResult(2, tmp_arg1);
+		     StoreBifResult(4, Op1);
 		 }
 		 goto big_shift;
 	     }
-	 } else if (is_big(tmp_arg2)) {
+	 } else if (is_big(Op2)) {
 	     /*
 	      * N bsr NegativeBigNum == N bsl MAX_SMALL
 	      * N bsr PositiveBigNum == N bsl MIN_SMALL
 	      */
-	     tmp_arg2 = make_small(bignum_header_is_neg(*big_val(tmp_arg2)) ?
+	     Op2 = make_small(bignum_header_is_neg(*big_val(Op2)) ?
 				   MAX_SMALL : MIN_SMALL);
 	     goto do_bsl;
 	}
      goto badarith;
      
-     OpCase(i_bsl_jId):
+     OpCase(i_bsl_jIssd):
+         GetArg2(2, Op1, Op2);
+
  do_bsl:
-	 if (is_small(tmp_arg2)) {
-	     i = signed_val(tmp_arg2);
+	 if (is_small(Op2)) {
+	     i = signed_val(Op2);
 
-	     if (is_small(tmp_arg1)) {
+	     if (is_small(Op1)) {
 	     small_shift:
-		 ires = signed_val(tmp_arg1);
+		 ires = signed_val(Op1);
 	     
 		 if (i == 0 || ires == 0) {
-		     StoreBifResult(2, tmp_arg1);
+		     StoreBifResult(4, Op1);
 		 } else if (i < 0)  { /* Right shift */
 		     i = -i;
 		     if (i >= SMALL_BITS-1) {
-			 tmp_arg1 = (ires < 0) ? SMALL_MINUS_ONE : SMALL_ZERO;
+			 Op1 = (ires < 0) ? SMALL_MINUS_ONE : SMALL_ZERO;
 		     } else {
-			 tmp_arg1 = make_small(ires >> i);
+			 Op1 = make_small(ires >> i);
 		     }
-		     StoreBifResult(2, tmp_arg1);
+		     StoreBifResult(4, Op1);
 		 } else if (i < SMALL_BITS-1) { /* Left shift */
 		     if ((ires > 0 && ((~(Uint)0 << ((SMALL_BITS-1)-i)) & ires) == 0) ||
 			 ((~(Uint)0 << ((SMALL_BITS-1)-i)) & ~ires) == 0) {
-			 tmp_arg1 = make_small(ires << i);
-			 StoreBifResult(2, tmp_arg1);
+			 Op1 = make_small(ires << i);
+			 StoreBifResult(4, Op1);
 		     }
 		 }
-		 tmp_arg1 = small_to_big(ires, tmp_big);
+		 Op1 = small_to_big(ires, tmp_big);
 
 	     big_shift:
 		 if (i > 0) {	/* Left shift. */
-		     ires = big_size(tmp_arg1) + (i / D_EXP);
+		     ires = big_size(Op1) + (i / D_EXP);
 		 } else {	/* Right shift. */
-		     ires = big_size(tmp_arg1);
+		     ires = big_size(Op1);
 		     if (ires <= (-i / D_EXP))
 			 ires = 3; /* ??? */
 		     else
@@ -2998,14 +2959,14 @@ do {						\
 			 c_p->freason = SYSTEM_LIMIT;
 			 goto lb_Cl_error;
 		     }
-		     TestHeapPreserve(ires+1, Arg(1), tmp_arg1);
+		     TestHeapPreserve(ires+1, Arg(1), Op1);
 		     bigp = HTOP;
-		     tmp_arg1 = big_lshift(tmp_arg1, i, bigp);
-		     if (is_big(tmp_arg1)) {
+		     Op1 = big_lshift(Op1, i, bigp);
+		     if (is_big(Op1)) {
 			 HTOP += bignum_header_arity(*HTOP) + 1;
 		     }
 		     HEAP_SPACE_VERIFIED(0);
-		     if (is_nil(tmp_arg1)) {
+		     if (is_nil(Op1)) {
 			 /*
 			  * This result must have been only slight larger
 			  * than allowed since it wasn't caught by the
@@ -3015,25 +2976,25 @@ do {						\
 			 goto lb_Cl_error;
 		     }
 		     ERTS_HOLE_CHECK(c_p);
-		     StoreBifResult(2, tmp_arg1);
+		     StoreBifResult(4, Op1);
 		 }
-	     } else if (is_big(tmp_arg1)) {
+	     } else if (is_big(Op1)) {
 		 if (i == 0) {
-		     StoreBifResult(2, tmp_arg1);
+		     StoreBifResult(4, Op1);
 		 }
 		 goto big_shift;
 	     }
-	 } else if (is_big(tmp_arg2)) {
-	     if (bignum_header_is_neg(*big_val(tmp_arg2))) {
+	 } else if (is_big(Op2)) {
+	     if (bignum_header_is_neg(*big_val(Op2))) {
 		 /*
 		  * N bsl NegativeBigNum is either 0 or -1, depending on
 		  * the sign of N. Since we don't believe this case
 		  * is common, do the calculation with the minimum
 		  * amount of code.
 		  */
-		 tmp_arg2 = make_small(MIN_SMALL);
+		 Op2 = make_small(MIN_SMALL);
 		 goto do_bsl;
-	     } else if (is_small(tmp_arg1) || is_big(tmp_arg1)) {
+	     } else if (is_small(Op1) || is_big(Op1)) {
 		 /*
 		  * N bsl PositiveBigNum is too large to represent.
 		  */