Tighten up condition code handling in the back end, so as to placate

IBM's BEAM checker.  There is no error in the existing code.  However
BEAM doesn't know that when PPCCondCode::test == Pct_ALWAYS then the
::flag field is irrelevant, and so it believes it is being used
uninitialised.  Add a Pcf_NONE ::flag value for use in that case, and
add assertions to match.  (Untested!)

git-svn-id: svn://svn.valgrind.org/vex/trunk@2144

diff --git a/VEX/priv/host_ppc_defs.c b/VEX/priv/host_ppc_defs.c
index b0b9b08a769bb28ab63901877f5d18ad76b6d117..2065824acf99e8bd280ee5272f6213b7e2cda392 100644 (file)
--- a/VEX/priv/host_ppc_defs.c
+++ b/VEX/priv/host_ppc_defs.c
@@ -286,6 +286,8 @@ HChar* showPPCCondCode ( PPCCondCode cond )
       return (cond.test == Pct_TRUE) ? "cr7.gt=1" : "cr7.gt=0";
    case Pcf_7LT:
       return (cond.test == Pct_TRUE) ? "cr7.lt=1" : "cr7.lt=0";
+   case Pcf_NONE:
+      return "no-flag";
    default: vpanic("ppPPCCondCode");
    }
 }
@@ -296,6 +298,11 @@ PPCCondCode mk_PPCCondCode ( PPCCondTest test, PPCCondFlag flag )
    PPCCondCode cc;
    cc.flag = flag;
    cc.test = test;
+   if (test == Pct_ALWAYS) { 
+      vassert(flag == Pcf_NONE);
+   } else {
+      vassert(flag != Pcf_NONE);
+   }
    return cc;
 }
 
@@ -3152,6 +3159,7 @@ Int emit_PPCInstr ( UChar* buf, Int nbuf, PPCInstr* i,
          // Just load 1 to dst => li dst,1
          p = mkFormD(p, 14, r_dst, 0, 1);
       } else {
+         vassert(cond.flag != Pcf_NONE);
          rot_imm = 1 + cond.flag;
          r_tmp = 0;  // Not set in getAllocable, so no need to declare.
 

diff --git a/VEX/priv/host_ppc_defs.h b/VEX/priv/host_ppc_defs.h
index f93a2104c655778dbd7b7dc38882cc192f08be64..c2bde5cdd2762da5b5fecfd433eceb89b7394c3d 100644 (file)
--- a/VEX/priv/host_ppc_defs.h
+++ b/VEX/priv/host_ppc_defs.h
@@ -162,15 +162,16 @@ typedef
       Pcf_7LT  = 28,  /* neg  | lt          */
       Pcf_7GT  = 29,  /* pos  | gt          */
       Pcf_7EQ  = 30,  /* zero | equal       */
-      Pcf_7SO  = 31   /* summary overflow   */
+      Pcf_7SO  = 31,  /* summary overflow   */
+      Pcf_NONE = 32   /* no condition; used with Pct_ALWAYS */
    }
    PPCCondFlag;
 
 typedef
    enum {   /* Maps bc bitfield BO */
-      Pct_FALSE  = 0x4,
-      Pct_TRUE   = 0xC,
-      Pct_ALWAYS = 0x14
+      Pct_FALSE  = 0x4, /* associated PPCCondFlag must not be Pcf_NONE */
+      Pct_TRUE   = 0xC, /* associated PPCCondFlag must not be Pcf_NONE */
+      Pct_ALWAYS = 0x14 /* associated PPCCondFlag must be Pcf_NONE */
    }
    PPCCondTest;
 

diff --git a/VEX/priv/host_ppc_isel.c b/VEX/priv/host_ppc_isel.c
index 0f82e85c91ac6a23db4a9512e48f13935725a0dd..7ea845051805de2e3b1bd0acac2e70166b5dde5b 100644 (file)
--- a/VEX/priv/host_ppc_isel.c
+++ b/VEX/priv/host_ppc_isel.c
@@ -785,7 +785,7 @@ void doHelperCall ( ISelEnv* env,
       }
 
       /* Fast scheme only applies for unconditional calls.  Hence: */
-      cc.test = Pct_ALWAYS;
+      cc = mk_PPCCondCode( Pct_ALWAYS, Pcf_NONE );
 
    } else {
 
@@ -828,7 +828,7 @@ void doHelperCall ( ISelEnv* env,
          because the argument computations could trash the condition
          codes.  Be a bit clever to handle the common case where the
          guard is 1:Bit. */
-      cc.test = Pct_ALWAYS;
+      cc = mk_PPCCondCode( Pct_ALWAYS, Pcf_NONE );
       if (guard) {
          if (guard->tag == Iex_Const 
              && guard->Iex.Const.con->tag == Ico_U1