Fix LDR not assigning immediate as memory offset.

See: capstone-engine#2015 (comment)

Author: Rot127

arch/AArch64/AArch64Mapping.c

@@ -2559,6 +2559,17 @@ void AArch64_set_detail_op_reg(MCInst *MI, unsigned OpNum, aarch64_reg Reg)
 	AArch64_inc_op_count(MI);
 }
 
+/// Check if the previous operand is a memory operand
+/// with only the base register set AND if this base register
+/// is write-back.
+/// This indicates the following immediate is a post-indexed
+/// memory offset.
+static bool prev_is_membase_wb(MCInst *MI) {
+	return AArch64_get_detail_op(MI, -1)->type == AARCH64_OP_MEM &&
+	       AArch64_get_detail_op(MI, -1)->mem.disp == 0 &&
+	       get_detail(MI)->writeback;
+}
+
 /// Adds an immediate AArch64 operand at position OpNum and increases the op_count
 /// by one.
 void AArch64_set_detail_op_imm(MCInst *MI, unsigned OpNum,
@@ -2581,7 +2592,7 @@ void AArch64_set_detail_op_imm(MCInst *MI, unsigned OpNum,
 		}
 		return;
 	}
-	if (map_get_op_type(MI, OpNum) & CS_OP_MEM) {
+	if (map_get_op_type(MI, OpNum) & CS_OP_MEM || prev_is_membase_wb(MI)) {
 		AArch64_set_detail_op_mem(MI, OpNum, Imm);
 		return;
 	}
@@ -2635,7 +2646,6 @@ void AArch64_set_detail_op_mem(MCInst *MI, unsigned OpNum, uint64_t Val)
 	if (!detail_is_set(MI))
 		return;
 	AArch64_check_safe_inc();
-	assert(map_get_op_type(MI, OpNum) & CS_OP_MEM);
 
 	AArch64_set_mem_access(MI, true);
 
@@ -2644,7 +2654,6 @@ void AArch64_set_detail_op_mem(MCInst *MI, unsigned OpNum, uint64_t Val)
 	default:
 		assert(0 && "Secondary type not supported yet.");
 	case CS_OP_REG: {
-		assert(secondary_type == CS_OP_REG);
 		bool is_index_reg = AArch64_get_detail_op(MI, 0)->mem.base !=
 				    AARCH64_REG_INVALID;
 		if (is_index_reg)
@@ -2666,7 +2675,6 @@ void AArch64_set_detail_op_mem(MCInst *MI, unsigned OpNum, uint64_t Val)
 		break;
 	}
 	case CS_OP_IMM: {
-		assert(secondary_type == CS_OP_IMM);
 		AArch64_get_detail_op(MI, 0)->mem.disp = Val;
 		break;
 	}

tests/details/aarch64.yaml

@@ -361,10 +361,7 @@ test_cases:
             -
               type: AARCH64_OP_MEM
               mem_base: sp
-              access: CS_AC_READ
-            -
-              type: AARCH64_OP_IMM
-              imm: 0x3c
+              mem_disp: 0x3c
               access: CS_AC_READ
             post_indexed: 1
             cc: AArch64CC_Invalid

tests/issues/issues.yaml

@@ -5411,3 +5411,30 @@ test_cases:
                 mem_base: x0
                 access: CS_AC_READ_WRITE
           regs_read: [ w1, w2, x0 ]
+  -
+    input:
+      name: "issue ldr offset as imm: https://github.com/capstone-engine/capstone/issues/2015#issuecomment-2373660217"
+      bytes: [ 0x01, 0xa4, 0x40, 0xf8 ]
+      arch: "CS_ARCH_AARCH64"
+      options: [ CS_OPT_DETAIL ]
+      address: 0x0
+    expected:
+      insns:
+      -
+        asm_text: "ldr	x1, [x0], #0xa"
+        details:
+          aarch64:
+            operands:
+              -
+                type: AARCH64_OP_REG
+                reg: x1
+                access: CS_AC_WRITE
+              -
+                type: AARCH64_OP_MEM
+                mem_base: x0
+                mem_disp: 0xa
+                access: CS_AC_READ
+            post_indexed: 1
+          writeback: 1
+          regs_read: [ x0 ]
+          regs_write: [ x0, x1 ]