Remove code duplication from the dispatchers. Keep the core loop

in common.
To accomplish that without penalizing the non-profiling dispatcher
we do the stats gathering *after* the jitted code returns to the
dispatcher. For that to work properly, we need to stash away the
instruction adddress before entering the jitted code so we can use
it later. (See also VEX r2208).

Two other tweaks are included here:
(1) For the non-profiling dispatcher it is not necessary to update
    the LR in each iteration. Quite obviously the jitted code cannot
    modify the LR in its iteration because it needs it at the very end
    when it returns. So we move this step out of the core loop.
(2) Move loading the address of VG_(tt_fast) past testing for a changed
    guest state pointer.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12044

diff --git a/coregrind/m_dispatch/dispatch-s390x-linux.S b/coregrind/m_dispatch/dispatch-s390x-linux.S
index a3fbab440c44101639bf9bd97d73ebeafa699e3e..97c4d934c36acf66a1bf5a7b08ceee69aa8b5440 100644 (file)
--- a/coregrind/m_dispatch/dispatch-s390x-linux.S
+++ b/coregrind/m_dispatch/dispatch-s390x-linux.S
@@ -58,6 +58,9 @@
 /* Location of saved guest state pointer */
 #define S390_LOC_SAVED_GSP S390_OFFSET_SAVED_GSP(SP)
 
+/* Location of saved R2 register */
+#define S390_LOC_SAVED_R2 S390_OFFSET_SAVED_R2(SP)
+
 /*----------------------------------------------------*/
 /*--- Preamble (set everything up)                 ---*/
 /*----------------------------------------------------*/
@@ -126,6 +129,15 @@ VG_(run_innerloop):
 /*----------------------------------------------------*/
 
 run_innerloop__dispatch_unprofiled:
+        /* Load the link register with the address the jitted code will
+           return to when it's done executing. The link register is loaded
+           exactly once per loop. This is safe, because the jitted code 
+           cannot possibly modify the LR. How else would it be able to return
+           to the location in the LR otherwise? */
+        basr LR,0
+
+        /* Loop begins here */
+        
         /* This is the story:
 
            r2  = IA = next guest address
@@ -134,11 +146,10 @@ run_innerloop__dispatch_unprofiled:
                  special value
            r15 = stack pointer (as usual)
         */
-
+innermost_loop: 
         /* Has the guest state pointer been messed with? If yes, exit.
            The mess is recognised by r13 containing an odd value. */
         tmll %r13,1
-        larl %r8, VG_(tt_fast)
         jne  gsp_changed
 
         /* Save the jump address in the guest state */
@@ -157,6 +168,7 @@ run_innerloop__dispatch_unprofiled:
            which is
            offset = ((addr & (VG_TT_FAST_MASK << 1) ) << 3
         */
+        larl  %r8, VG_(tt_fast)
         llill %r5,( VG_TT_FAST_MASK << 1) & 0xffff
 #if ((( VG_TT_FAST_MASK << 1) & 0xffff0000) >> 16 != 0)
         iilh %r5,(( VG_TT_FAST_MASK << 1) & 0xffff0000) >> 16
@@ -164,11 +176,6 @@ run_innerloop__dispatch_unprofiled:
         ngr  %r5,%r2
         sllg %r7,%r5,3
 
-        /* Set the return address to the beginning of the loop here to
-           have some instruction between setting r7 and using it as an
-           address */
-       larl LR,run_innerloop__dispatch_unprofiled
-
        /* Are we out of timeslice?  If yes, defer to scheduler. */
         ahi  S390_REGNO_DISPATCH_CTR,-1
         jz   counter_is_zero
@@ -190,66 +197,29 @@ run_innerloop__dispatch_unprofiled:
 /*----------------------------------------------------*/
 
 run_innerloop__dispatch_profiled:
+        stg  %r2,S390_LOC_SAVED_R2
 
-        /* Has the guest state pointer been messed with?  If yes, exit.
-           The mess is recognised by r13 containing an odd value. */
-        tmll %r13,1
-        larl %r8, VG_(tt_fast)
-        jne  gsp_changed
-
-        /* Save the jump address in the guest state */
-        stg  %r2,OFFSET_s390x_IA(%r13)
-
-       /* Try a fast lookup in the translation cache:
-           Compute offset (not index) into VT_(tt_fast):
+        /* Load the link register with the address the jitted code will
+           return to when it's done executing. */
+        bras LR,innermost_loop
 
-           offset = VG_TT_FAST_HASH(addr) * sizeof(FastCacheEntry)
-
-           with VG_TT_FAST_HASH(addr) == (addr >> 1) & VG_TT_FAST_MASK
-           and  sizeof(FastCacheEntry) == 16
+        /* Jitted code returns here. Update profile counter for previous IA */
 
-           offset = ((addr >> 1) & VG_TT_FAST_MASK) << 4
-           which is
-           offset = ((addr & (VG_TT_FAST_MASK << 1) ) << 3
-        */
         llill %r5,( VG_TT_FAST_MASK << 1) & 0xffff
 #if ((( VG_TT_FAST_MASK << 1) & 0xffff0000) >> 16 != 0)
         iilh %r5,(( VG_TT_FAST_MASK << 1) & 0xffff0000) >> 16
 #endif
-        ngr  %r5,%r2
-        sllg %r7,%r5,3
-
-        /* Set the return address to the beginning of the loop here to
-           have some instruction between setting r7 and using it as an
-           address */
-       larl LR,run_innerloop__dispatch_profiled
-
-       /* Are we out of timeslice?  If yes, defer to scheduler. */
-        ahi  S390_REGNO_DISPATCH_CTR,-1
-        jz   counter_is_zero
-
-        lg   %r11, 8(%r8,%r7)      /* .host */
-        cg   %r2,  0(%r8,%r7)      /* next guest address == .guest ? */
-        jne  fast_lookup_failed
-
-        /* sizeof(FastCacheEntry) == 16, sizeof(*UInt)==8 */
-        srlg %r7,%r7,1
+        ng   %r5,S390_LOC_SAVED_R2
+        sllg %r7,%r5,2
 
-        /* we got a hit: VG_(tt_fastN) is guaranteed to point to count */
+        /* Increment bb profile counter */
         larl %r8, VG_(tt_fastN)
-
-        /* increment bb profile counter */
         lg   %r9,0(%r8,%r7)
         l    %r10,0(%r9)
         ahi  %r10,1
         st   %r10,0(%r9)
 
-        /* Found a match.  Call .host.
-           r11 is an address. There we will find the instrumented client code.
-           That code may modify the guest state register r13. The client code
-           will return to the beginning of this loop start by issuing br LR.
-           We can simply branch to the host code */
-        br %r11
+        j    run_innerloop__dispatch_profiled
 
 /*----------------------------------------------------*/
 /*--- exit points                                  ---*/