sedymrak wrote:
Steps for reproducing 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 0e99451c3b70..a4b51db3e56d 100644
--- a/lldb/source/Utility/RegisterValue.cpp
+++ b/lldb/source/Utility/RegisterValue.cpp
@@ -188,6 +188,7 @@ Status RegisterValue::SetValueFromData(const RegisterInfo
®_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
®_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)
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.
https://github.com/llvm/llvm-project/pull/163646
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