Re: [Qemu-devel] Shifts, ppc[64], xtensa

[malc]

On Tue, 18 Sep 2012, Richard Henderson wrote:

> On 09/18/2012 12:52 PM, malc wrote:
> >      case INDEX_op_shl_i32:
> >          if (const_args[2]) {
> > +            if (args[2] > 31) {
> > +                tcg_out_movi (s, TCG_TYPE_I32, 0, args[2]);
> > +                tcg_out32 (s, SLW | SAB (args[1], args[0], 0));
> > +            }
> 
> What's this bit for?

This bit is to offset for the fact that i haven't slept in a while, and...

> 
> AFAIK all you should need are the added & 31 below.
> 

Not really - due to the 0 corner case, following should be better:

diff --git a/tcg/ppc/tcg-target.c b/tcg/ppc/tcg-target.c
index 26c4b33..784b157 100644
--- a/tcg/ppc/tcg-target.c
+++ b/tcg/ppc/tcg-target.c
@@ -409,6 +409,7 @@ static int tcg_target_const_match(tcg_target_long val,
 
 #define TW     XO31(4)
 #define TRAP   (TW | TO (31))
+#define NOP    0x60000000
 
 #define RT(r) ((r)<<21)
 #define RS(r) ((r)<<21)
@@ -1306,10 +1307,10 @@ void ppc_tb_set_jmp_target (unsigned long jmp_addr, 
unsigned long addr)
             *ptr = 0x48000000 | (disp & 0x03fffffc); /* b disp */
             patch_size = 4;
         } else {
-            ptr[0] = 0x60000000; /* nop */
-            ptr[1] = 0x60000000;
-            ptr[2] = 0x60000000;
-            ptr[3] = 0x60000000;
+            ptr[0] = NOP;
+            ptr[1] = NOP;
+            ptr[2] = NOP;
+            ptr[3] = NOP;
             patch_size = 16;
         }
     }
@@ -1330,7 +1331,10 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, 
const TCGArg *args,
             /* direct jump method */
 
             s->tb_jmp_offset[args[0]] = s->code_ptr - s->code_buf;
-            s->code_ptr += 16;
+            tcg_out32 (s, NOP);
+            tcg_out32 (s, NOP);
+            tcg_out32 (s, NOP);
+            tcg_out32 (s, NOP);
         }
         else {
             tcg_abort ();
@@ -1565,35 +1569,54 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, 
const TCGArg *args,
 
     case INDEX_op_shl_i32:
         if (const_args[2]) {
-            tcg_out32 (s, (RLWINM
-                           | RA (args[0])
-                           | RS (args[1])
-                           | SH (args[2])
-                           | MB (0)
-                           | ME (31 - args[2])
-                           )
-                );
+            int sh = args[2] & 31;
+            if (!sh) {
+                tcg_out_mov (s, TCG_TYPE_I32, args[0], args[1]);
+            }
+            else {
+                tcg_out32 (s, (RLWINM
+                               | RA (args[0])
+                               | RS (args[1])
+                               | SH (sh)
+                               | MB (0)
+                               | ME (31 - sh)
+                               )
+                    );
+            }
         }
         else
             tcg_out32 (s, SLW | SAB (args[1], args[0], args[2]));
         break;
     case INDEX_op_shr_i32:
         if (const_args[2]) {
-            tcg_out32 (s, (RLWINM
-                           | RA (args[0])
-                           | RS (args[1])
-                           | SH (32 - args[2])
-                           | MB (args[2])
-                           | ME (31)
-                           )
-                );
+            int sh = args[2] & 31;
+            if (!sh) {
+                tcg_out_mov (s, TCG_TYPE_I32, args[0], args[1]);
+            }
+            else {
+                tcg_out32 (s, (RLWINM
+                               | RA (args[0])
+                               | RS (args[1])
+                               | SH (32 - sh)
+                               | MB (sh)
+                               | ME (31)
+                               )
+                    );
+            }
         }
         else
             tcg_out32 (s, SRW | SAB (args[1], args[0], args[2]));
         break;
     case INDEX_op_sar_i32:
-        if (const_args[2])
-            tcg_out32 (s, SRAWI | RS (args[1]) | RA (args[0]) | SH (args[2]));
+        if (const_args[2]) {
+            int sh = args[2] & 31;
+            if (!sh) {
+                tcg_out_mov (s, TCG_TYPE_I32, args[0], args[1]);
+            }
+            else {
+                tcg_out32 (s, SRAWI | RS (args[1]) | RA (args[0]) | SH (sh));
+            }
+        }
         else
             tcg_out32 (s, SRAW | SAB (args[1], args[0], args[2]));
         break;
@@ -1604,7 +1627,7 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, 
const TCGArg *args,
                 | RS (args[1])
                 | MB (0)
                 | ME (31)
-                | (const_args[2] ? RLWINM | SH (args[2])
+                | (const_args[2] ? RLWINM | SH (args[2] & 31)
                                  : RLWNM | RB (args[2]))
                 ;
             tcg_out32 (s, op);


This expects deposit/rotr constant arguments to be sane,
i'm no longer certain this assumption is a sane one though...

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