[lldb] Fix the "RegisterValue::SetValueFromData" method for 128-bit integer registers (llvm#163646)

Fix the `RegisterValue::SetValueFromData` method so that it works also
for 128-bit registers that contain integers.

Without this change, the `RegisterValue::SetValueFromData` method does
not work correctly
for 128-bit registers that contain (signed or unsigned) integers.

---

Steps to reproduce the problem:

(1)

Create a program that writes a 128-bit number to a 128-bit registers
`xmm0`. E.g.:
```
#include <stdint.h>

int main() {
  __asm__ volatile (
      "pinsrq $0, %[lo], %%xmm0\n\t"  // insert low 64 bits
      "pinsrq $1, %[hi], %%xmm0"    // insert high 64 bits
      :
      : [lo]"r"(0x7766554433221100),
        [hi]"r"(0xffeeddccbbaa9988)
  );
  return 0;
}
```

(2)

Compile this program with LLVM compiler:
```
$ $YOUR/clang -g -o main main.c
```

(3)

Modify LLDB so that when it will be reading value from the `xmm0`
register, instead of assuming that it is vector register, it will treat
it as if it contain an integer. This can be achieved e.g. this way:
```
diff --git a/lldb/source/Utility/RegisterValue.cpp b/lldb/source/Utility/RegisterValue.cpp
index 0e99451..a4b51db3e56d 100644
--- a/lldb/source/Utility/RegisterValue.cpp
+++ b/lldb/source/Utility/RegisterValue.cpp
@@ -188,6 +188,7 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     break;
   case eEncodingUint:
   case eEncodingSint:
+  case eEncodingVector:
     if (reg_info.byte_size == 1)
       SetUInt8(src.GetMaxU32(&src_offset, src_len));
     else if (reg_info.byte_size <= 2)
@@ -217,23 +218,6 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     else if (reg_info.byte_size == sizeof(long double))
       SetLongDouble(src.GetLongDouble(&src_offset));
     break;
-  case eEncodingVector: {
-    m_type = eTypeBytes;
-    assert(reg_info.byte_size <= kMaxRegisterByteSize);
-    buffer.bytes.resize(reg_info.byte_size);
-    buffer.byte_order = src.GetByteOrder();
-    if (src.CopyByteOrderedData(
-            src_offset,          // offset within "src" to start extracting data
-            src_len,             // src length
-            buffer.bytes.data(), // dst buffer
-            buffer.bytes.size(), // dst length
-            buffer.byte_order) == 0) // dst byte order
-    {
-      error = Status::FromErrorStringWithFormat(
-          "failed to copy data for register write of %s", reg_info.name);
-      return error;
-    }
-  }
   }
 
   if (m_type == eTypeInvalid)
```

(4)

Rebuild the LLDB.

(5)

Observe what happens how LLDB will print the content of this register
after it was initialized with 128-bit value.
```
$YOUR/lldb --source ./main
(lldb) target create main
Current executable set to '.../main' (x86_64).
(lldb) breakpoint set --file main.c --line 11
Breakpoint 1: where = main`main + 45 at main.c:11:3, address = 0x000000000000164d
(lldb) settings set stop-line-count-before 20
(lldb) process launch
Process 2568735 launched: '.../main' (x86_64)
Process 2568735 stopped
* thread #1, name = 'main', stop reason = breakpoint 1.1
    frame #0: 0x000055555555564d main`main at main.c:11:3
   1   	#include <stdint.h>
   2   	
   3   	int main() {
   4   	  __asm__ volatile (
   5   	      "pinsrq $0, %[lo], %%xmm0\n\t"  // insert low 64 bits
   6   	      "pinsrq $1, %[hi], %%xmm0"    // insert high 64 bits
   7   	      :
   8   	      : [lo]"r"(0x7766554433221100),
   9   	        [hi]"r"(0xffeeddccbbaa9988)
   10  	  );
-> 11  	  return 0;
   12  	}
(lldb) register read --format hex xmm0
    xmm0 = 0x7766554433221100ffeeddccbbaa9988
```

You can see that the upper and lower 64-bit wide halves are swapped.

---------

Co-authored-by: Matej Košík <[email protected]>

Author: sedymrak

lldb/source/Utility/RegisterValue.cpp

@@ -199,7 +199,7 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     else if (reg_info.byte_size <= 16) {
       uint64_t data1 = src.GetU64(&src_offset);
       uint64_t data2 = src.GetU64(&src_offset);
-      if (src.GetByteOrder() == eByteOrderBig) {
+      if (src.GetByteOrder() == eByteOrderLittle) {
         int128.x[0] = data1;
         int128.x[1] = data2;
       } else {

lldb/unittests/Utility/RegisterValueTest.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Utility/RegisterValue.h"
+#include "lldb/Utility/DataExtractor.h"
+#include "lldb/lldb-private-types.h"
 #include "gtest/gtest.h"
 #include <optional>
 
@@ -54,3 +56,41 @@ TEST(RegisterValueTest, GetScalarValue) {
             Scalar((APInt(128, 0xffeeddccbbaa9988ull) << 64) |
                    APInt(128, 0x7766554433221100)));
 }
+
+static const Scalar etalon128(APInt(128, 0xffeeddccbbaa9988ull) << 64 |
+                              APInt(128, 0x7766554433221100ull));
+
+void TestSetValueFromData128(void *src, const lldb::ByteOrder endianness) {
+  RegisterInfo ri{"uint128_register",
+                  nullptr,
+                  16,
+                  0,
+                  lldb::Encoding::eEncodingUint,
+                  lldb::Format::eFormatDefault,
+                  {0, 0, 0, LLDB_INVALID_REGNUM, 0},
+                  nullptr,
+                  nullptr,
+                  nullptr};
+  DataExtractor src_extractor(src, 16, endianness, 8);
+  RegisterValue rv;
+  EXPECT_TRUE(rv.SetValueFromData(ri, src_extractor, 0, false).Success());
+  Scalar s;
+  EXPECT_TRUE(rv.GetScalarValue(s));
+  EXPECT_EQ(s, etalon128);
+}
+
+// Test that the "RegisterValue::SetValueFromData" method works correctly
+// with 128-bit little-endian data that represents an integer.
+TEST(RegisterValueTest, SetValueFromData_128_le) {
+  uint8_t src[] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
+                   0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff};
+  TestSetValueFromData128(src, lldb::ByteOrder::eByteOrderLittle);
+}
+
+// Test that the "RegisterValue::SetValueFromData" method works correctly
+// with 128-bit big-endian data that represents an integer.
+TEST(RegisterValueTest, SetValueFromData_128_be) {
+  uint8_t src[] = {0xff, 0xee, 0xdd, 0xcc, 0xbb, 0xaa, 0x99, 0x88,
+                   0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11, 0x00};
+  TestSetValueFromData128(src, lldb::ByteOrder::eByteOrderBig);
+}