We use the VSCBIQ/VSBIQ/VSBCBIQ family of instructions to implement
USUBO/USUBO_CARRY for the i128 data type. However, these instructions
use an inverted sense of the borrow indication flag (a value of 1
indicates *no* borrow, while a value of 0 indicated borrow). This
does not match the semantics of the boolean "overflow" flag of the
USUBO/USUBO_CARRY ISD nodes.
Fix this by generating code to explicitly invert the flag. These
cancel out of the result of USUBO feeds into an USUBO_CARRY.
To avoid unnecessary zero-extend operations, also improve the
DAGCombine handling of ZERO_EXTEND to optimize (zext (xor (trunc)))
sequences where appropriate.
Fixes: https://github.com/llvm/llvm-project/issues/83268
We use the VSCBIQ/VSBIQ/VSBCBIQ family of instructions to implement
USUBO/USUBO_CARRY for the i128 data type. However, these instructions
use an inverted sense of the borrow indication flag (a value of 1
indicates *no* borrow, while a value of 0 indicated borrow). This
does not match the semantics of the boolean "overflow" flag of the
USUBO/USUBO_CARRY ISD nodes.
Fix this by generating code to explicitly invert the flag. These
cancel out of the result of USUBO feeds into an USUBO_CARRY.
To avoid unnecessary zero-extend operations, also improve the
DAGCombine handling of ZERO_EXTEND to optimize (zext (xor (trunc)))
sequences where appropriate.
Fixes: https://github.com/llvm/llvm-project/issues/83268
On processors supporting vector registers and SIMD instructions, enable
i128 as legal type in VRs. This allows many operations to be implemented
via native instructions directly in VRs (including add, subtract,
logical operations and shifts). For a few other operations (e.g.
multiply and divide, as well as atomic operations), we need to move the
i128 value back to a GPR pair to use the corresponding instruction
there. Overall, this is still beneficial.
The patch includes the following LLVM changes:
- Enable i128 as legal type
- Set up legal operations (in SystemZInstrVector.td)
- Custom expansion for i128 add/subtract with carry
- Custom expansion for i128 comparisons and selects
- Support for moving i128 to/from GPR pairs when required
- Handle 128-bit integer constant values everywhere
- Use i128 as intrinsic operand type where appropriate
- Updated and new test cases
In addition, clang builtins are updated to reflect the intrinsic operand
type changes (which also improves compatibility with GCC).
