Fix bug 303963.

Emulation of PCMPxSTRx mode 0x0C was wrong
for searching an empty needle in an empty haystack.

git-svn-id: svn://svn.valgrind.org/vex/trunk@2447

diff --git a/VEX/priv/guest_generic_x87.c b/VEX/priv/guest_generic_x87.c
index a10f86990e9634da650a63825847e81ed477febd..ae627f64f0ce40ed92906f77f232aa239d5c5b1d 100644 (file)
--- a/VEX/priv/guest_generic_x87.c
+++ b/VEX/priv/guest_generic_x87.c
@@ -895,9 +895,6 @@ Bool compute_PCMPxSTRx ( /*OUT*/V128* resV,
       UInt   validL  = ~(zmaskL | -zmaskL);  // not(left(zmaskL))
       UInt   validR  = ~(zmaskR | -zmaskR);  // not(left(zmaskR))
       for (hi = 0; hi < 16; hi++) {
-         if ((validL & (1 << hi)) == 0)
-            // run off the end of the haystack
-            break;
          UInt m = 1;
          for (ni = 0; ni < 16; ni++) {
             if ((validR & (1 << ni)) == 0) break;
@@ -906,6 +903,9 @@ Bool compute_PCMPxSTRx ( /*OUT*/V128* resV,
             if (argL[i] != argR[ni]) { m = 0; break; }
          }
          boolRes |= (m << hi);
+         if ((validL & (1 << hi)) == 0)
+            // run off the end of the haystack
+            break;
       }
 
       // boolRes is "pre-invalidated"
@@ -1105,9 +1105,6 @@ Bool compute_PCMPxSTRx_wide ( /*OUT*/V128* resV,
       UInt    validL  = ~(zmaskL | -zmaskL);  // not(left(zmaskL))
       UInt    validR  = ~(zmaskR | -zmaskR);  // not(left(zmaskR))
       for (hi = 0; hi < 8; hi++) {
-         if ((validL & (1 << hi)) == 0)
-            // run off the end of the haystack
-            break;
          UInt m = 1;
          for (ni = 0; ni < 8; ni++) {
             if ((validR & (1 << ni)) == 0) break;
@@ -1116,6 +1113,9 @@ Bool compute_PCMPxSTRx_wide ( /*OUT*/V128* resV,
             if (argL[i] != argR[ni]) { m = 0; break; }
          }
          boolRes |= (m << hi);
+         if ((validL & (1 << hi)) == 0)
+            // run off the end of the haystack
+            break;
       }
 
       // boolRes is "pre-invalidated"