Do nothing for a repeated string instruction if ecx is 0

mehfooz09 · May 25, 2018 · 93788b4 · 93788b4
1 parent 01d919d
commit 93788b4
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Showing 2 changed files with 7 additions and 2 deletions.
diff --git a/emu/gadgets-x86/gadgets.h b/emu/gadgets-x86/gadgets.h
@@ -42,9 +42,9 @@
         cmpl TLB_ENTRY_page_if_writable(%_tlb,%r14), %r15d
     .endif
     movl %r15d, -TLB_entries+TLB_dirty_page(%_tlb)
-    je 2f
+    je 10f
     call handle_\type\()_miss
-2:
+10:
     addq TLB_ENTRY_data_minus_addr(%_tlb,%r14), %_addrq
 .endm
 

diff --git a/emu/gadgets-x86/string.S b/emu/gadgets-x86/string.S
@@ -15,7 +15,11 @@
     .endif
 
     .gadget \op\size\()_\rep
+        .ifc \rep,rep
+            testl %ecx, %ecx
+            jz 2f
     1:
+        .endif
         .ifc \op,stos
             movl %edi, %_addr
             write_prep
@@ -38,6 +42,7 @@
         .ifc \rep,rep
             decl %ecx
             jnz 1b
+    2:
         .endif
         gret 1
 .endm