X86Assembler: Support printing negative integers

Author: ubaidsk

src/libasr/codegen/x86_assembler.cpp

@@ -133,6 +133,21 @@ void emit_print_int(X86Assembler &a, const std::string &name)
     X86Reg base = X86Reg::ebp;
     // mov eax, [ebp+8]  // argument "i"
     a.asm_mov_r32_m32(X86Reg::eax, &base, nullptr, 1, 8);
+
+    a.asm_mov_r32_r32(X86Reg::ecx, X86Reg::eax); // make a copy in ecx
+    a.asm_mov_r32_imm32(X86Reg::ebx, 0);
+    a.asm_cmp_r32_r32(X86Reg::eax, X86Reg::ebx);
+    a.asm_jge_label(".print_int_"); // if num >= 0 then print it
+
+    // print "-" and then negate the integer
+    emit_print(a, "string-", 1U);
+    // ecx value changed during print so fetch back
+    a.asm_mov_r32_m32(X86Reg::ecx, &base, nullptr, 1, 8);
+    a.asm_neg_r32(X86Reg::ecx);
+
+    a.add_label(".print_int_");
+
+    a.asm_mov_r32_r32(X86Reg::eax, X86Reg::ecx); // fetch the val in ecx back to eax
     a.asm_xor_r32_r32(X86Reg::esi, X86Reg::esi);
 
     a.add_label(".loop");