x86: save prefixes to avoid expensive copying loop. based on idea of …

…Dang Hoang Vu
wodz · Jun 4, 2014 · 46b6693 · 46b6693
1 parent b76233c
commit 46b6693
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Showing 4 changed files with 15 additions and 10 deletions.
diff --git a/MCInst.h b/MCInst.h
@@ -149,7 +149,7 @@ struct MCInst {
 	// (Optional) instruction prefix, which can be up to 5 bytes.
 	// A prefix byte gets value 0 when irrelevant.
 	// This is copied from cs_x86 struct
-	uint8_t x86_prefix[5];
+	uint8_t x86_prefix[4];
 	bool x86_lock_rep;	// does this X86 insn contain LOCK/REP prefix?
 };
 

diff --git a/arch/X86/X86Disassembler.c b/arch/X86/X86Disassembler.c
@@ -698,6 +698,11 @@ static void update_pub_insn(cs_insn_flat *pub, InternalInstruction *inter, uint8
 		}
 	}
 
+	prefixes[0] = inter->prefix0;
+	prefixes[1] = inter->prefix1;
+	prefixes[2] = inter->prefix2;
+	prefixes[3] = inter->prefix3;
+
 	pub->x86.segment = x86_map_segment(inter->segmentOverride);
 
 	if (inter->vectorExtensionType > 0)
@@ -759,22 +764,17 @@ bool X86_getInstruction(csh ud, const uint8_t *code, size_t code_len,
 
 		return false;
 	} else {
-		int i, c;
-
 		*size = (uint16_t)insn.length;
 		result = (!translateInstruction(instr, &insn)) ?  true : false;
 		if (result) {
 			if (handle->detail)
 				update_pub_insn(&instr->flat_insn, &insn, instr->x86_prefix);
 			else {
 				// copy all prefixes
-				c = 0;
-				for(i = 0; i < 0x100; i++) {
-					if (insn.prefixPresent[i] > 0) {
-						instr->x86_prefix[c] = i;
-						c++;
-					}
-				}
+				instr->x86_prefix[0] = insn.prefix0;
+				instr->x86_prefix[1] = insn.prefix1;
+				instr->x86_prefix[2] = insn.prefix2;
+				instr->x86_prefix[3] = insn.prefix3;
 			}
 
 			instr->x86_lock_rep = insn.x86_lock_rep;

diff --git a/arch/X86/X86DisassemblerDecoder.c b/arch/X86/X86DisassemblerDecoder.c
@@ -460,6 +460,7 @@ static int readPrefixes(struct InternalInstruction* insn)
 					dbgprintf(insn, "Redundant Group 1 prefix");
 				prefixGroups[0] = TRUE;
 				setPrefixPresent(insn, byte, prefixLocation);
+				insn->prefix0 = byte;
 				break;
 			case 0x2e:  /* CS segment override -OR- Branch not taken */
 			case 0x36:  /* SS segment override -OR- Branch taken */
@@ -501,20 +502,23 @@ static int readPrefixes(struct InternalInstruction* insn)
 				insn->prefixPresent[0x64] = 0;
 				insn->prefixPresent[0x65] = 0;
 				setPrefixPresent(insn, byte, prefixLocation);
+				insn->prefix1 = byte;
 				break;
 			case 0x66:  /* Operand-size override */
 				if (prefixGroups[2])
 					dbgprintf(insn, "Redundant Group 3 prefix");
 				prefixGroups[2] = TRUE;
 				hasOpSize = TRUE;
 				setPrefixPresent(insn, byte, prefixLocation);
+				insn->prefix2 = byte;
 				break;
 			case 0x67:  /* Address-size override */
 				if (prefixGroups[3])
 					dbgprintf(insn, "Redundant Group 4 prefix");
 				prefixGroups[3] = TRUE;
 				hasAdSize = TRUE;
 				setPrefixPresent(insn, byte, prefixLocation);
+				insn->prefix3 = byte;
 				break;
 			default:    /* Not a prefix byte */
 				isPrefix = FALSE;

diff --git a/arch/X86/X86DisassemblerDecoder.h b/arch/X86/X86DisassemblerDecoder.h
@@ -570,6 +570,7 @@ typedef struct InternalInstruction {
 
   /* 1 if the prefix byte corresponding to the entry is present; 0 if not */
   uint8_t prefixPresent[0x100];
+  uint8_t prefix0, prefix1, prefix2, prefix3;
   /* contains the location (for use with the reader) of the prefix byte */
   uint64_t prefixLocations[0x100];
   /* The value of the vector extension prefix(EVEX/VEX/XOP), if present */