X86: Distinguish between the rep and repe prefixes.

STOS and MOVS only accept the rep prefix which always loops until rcx becomes
0. The other string instructions accept repe (same encoding as rep) and repne
which also check the condition code flags each iteration.

--HG--
extra : convert_revision : 544149f640302070810fb53e53bfeb0e87160ffc

src/arch/x86/isa/decoder/one_byte_opcodes.isa

@@ -332,8 +332,8 @@
             0x3: mov_Ov_rAX();
             0x4: StringInst::MOVS(Yb,Xb);
             0x5: StringInst::MOVS(Yv,Xv);
-            0x6: StringInst::CMPS(Yb,Xb);
+            0x6: StringTestInst::CMPS(Yb,Xb);
-            0x7: StringInst::CMPS(Yv,Xv);
+            0x7: StringTestInst::CMPS(Yv,Xv);
         }
         0x15: decode OPCODE_OP_BOTTOM3 {
             0x0: Inst::TEST(rAb,Ib);
@@ -342,8 +342,8 @@
             0x3: StringInst::STOS(Yv);
             0x4: lods_Al_Xb();
             0x5: lods_rAX_Xv();
-            0x6: StringInst::SCAS(Yb);
+            0x6: StringTestInst::SCAS(Yb);
-            0x7: StringInst::SCAS(Yv);
+            0x7: StringTestInst::SCAS(Yv);
         }
         format Inst {
             0x16: MOV(Bb,Ib);

src/arch/x86/isa/formats/string.isa

@@ -61,7 +61,7 @@
 //
 //////////////////////////////////////////////////////////////////////////
 
-def format StringInst(*opTypeSet) {{
+def format StringTestInst(*opTypeSet) {{
     allBlocks = OutputBlocks()
 
     regBlocks = specializeInst(Name, list(opTypeSet), EmulEnv())
@@ -86,3 +86,29 @@ def format StringInst(*opTypeSet) {{
     (header_output, decoder_output,
      decode_block, exec_output) = allBlocks.makeList()
 }};
+
+def format StringInst(*opTypeSet) {{
+    allBlocks = OutputBlocks()
+
+    regBlocks = specializeInst(Name, list(opTypeSet), EmulEnv())
+    eBlocks = specializeInst(Name + "_E", list(opTypeSet), EmulEnv())
+
+    for blocks in (regBlocks, eBlocks):
+        allBlocks.header_output += blocks.header_output
+        allBlocks.decoder_output += blocks.decoder_output
+        allBlocks.exec_output += blocks.exec_output
+
+    allBlocks.decode_block = '''
+        if (LEGACY_REP) {
+            %s
+        } else if (LEGACY_REPNE) {
+            // The repne prefix is illegal
+            return new MicroFault(machInst, "illprefix", new InvalidOpcode);
+        } else {
+            %s
+        }
+    ''' % (eBlocks.decode_block, regBlocks.decode_block)
+
+    (header_output, decoder_output,
+     decode_block, exec_output) = allBlocks.makeList()
+}};

src/arch/x86/isa/insts/general_purpose/string/move_string.py

@@ -82,25 +82,7 @@ topOfLoop:
     subi rcx, rcx, 1, flags=(EZF,), dataSize=asz
     add rdi, rdi, t3, dataSize=asz
     add rsi, rsi, t3, dataSize=asz
-    bri t0, label("topOfLoop"), flags=(CSTRZnEZF,)
+    bri t0, label("topOfLoop"), flags=(nCEZF,)
-    fault "NoFault"
-};
-
-def macroop MOVS_N_M_M {
-    # Find the constant we need to either add or subtract from rdi
-    ruflag t0, 10
-    movi t3, t3, dsz, flags=(CEZF,), dataSize=asz
-    subi t4, t0, dsz, dataSize=asz
-    mov t3, t3, t4, flags=(nCEZF,), dataSize=asz
-
-topOfLoop:
-    ld t1, seg, [1, t0, rsi]
-    st t1, es, [1, t0, rdi]
-
-    subi rcx, rcx, 1, flags=(EZF,), dataSize=asz
-    add rdi, rdi, t3, dataSize=asz
-    add rsi, rsi, t3, dataSize=asz
-    bri t0, label("topOfLoop"), flags=(CSTRnZnEZF,)
     fault "NoFault"
 };
 '''

src/arch/x86/isa/insts/general_purpose/string/store_string.py

@@ -78,23 +78,7 @@ topOfLoop:
 
     subi rcx, rcx, 1, flags=(EZF,), dataSize=asz
     add rdi, rdi, t3, dataSize=asz
-    bri t0, label("topOfLoop"), flags=(CSTRZnEZF,)
+    bri t0, label("topOfLoop"), flags=(nCEZF,)
-    fault "NoFault"
-};
-
-def macroop STOS_N_M {
-    # Find the constant we need to either add or subtract from rdi
-    ruflag t0, 10
-    movi t3, t3, dsz, flags=(CEZF,), dataSize=asz
-    subi t4, t0, dsz, dataSize=asz
-    mov t3, t3, t4, flags=(nCEZF,), dataSize=asz
-
-topOfLoop:
-    st rax, es, [1, t0, rdi]
-
-    subi rcx, rcx, 1, flags=(EZF,), dataSize=asz
-    add rdi, rdi, t3, dataSize=asz
-    bri t0, label("topOfLoop"), flags=(CSTRnZnEZF,)
     fault "NoFault"
 };
 '''