Set the writable and dead_on_unwind attributes for sret arguments. These
indicate that the argument points to writable memory (and it's legal to
introduce spurious writes to it on entry to the function) and that the
argument memory will not be used if the call unwinds.
This enables additional MemCpyOpt/DSE/LICM optimizations.
This patch deduces `noundef` attributes for return values.
IIUC, a function returns `noundef` values iff all of its return values
are guaranteed not to be `undef` or `poison`.
Definition of `noundef` from LangRef:
```
noundef
This attribute applies to parameters and return values. If the value representation contains any
undefined or poison bits, the behavior is undefined. Note that this does not refer to padding
introduced by the type’s storage representation.
```
Alive2: https://alive2.llvm.org/ce/z/g8Eis6
Compile-time impact: http://llvm-compile-time-tracker.com/compare.php?from=30dcc33c4ea3ab50397a7adbe85fe977d4a400bd&to=c5e8738d4bfbf1e97e3f455fded90b791f223d74&stat=instructions:u
|stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang|
|--|--|--|--|--|--|--|
|+0.01%|+0.01%|-0.01%|+0.01%|+0.03%|-0.04%|+0.01%|
The motivation of this patch is to reduce the number of `freeze` insts
and enable more optimizations.
Builtin function `__builtin_isfpclass` now can be called for a vector
of floating-point values. In this case it is applied to the vector
elementwise and produces vector of integer values.
Differential Revision: https://reviews.llvm.org/D153339
Builtin floating-point number classification functions:
- __builtin_isnan,
- __builtin_isinf,
- __builtin_finite, and
- __builtin_isnormal
now are implemented using `llvm.is_fpclass`.
This change makes the target callback `TargetCodeGenInfo::testFPKind`
unneeded. It is preserved in this change and should be removed later.
Differential Revision: https://reviews.llvm.org/D112932
A new builtin function __builtin_isfpclass is added. It is called as:
__builtin_isfpclass(<floating point value>, <test>)
and returns an integer value, which is non-zero if the floating point
argument falls into one of the classes specified by the second argument,
and zero otherwise. The set of classes is an integer value, where each
value class is represented by a bit. There are ten data classes, as
defined by the IEEE-754 standard, they are represented by bits:
0x0001 (__FPCLASS_SNAN) - Signaling NaN
0x0002 (__FPCLASS_QNAN) - Quiet NaN
0x0004 (__FPCLASS_NEGINF) - Negative infinity
0x0008 (__FPCLASS_NEGNORMAL) - Negative normal
0x0010 (__FPCLASS_NEGSUBNORMAL) - Negative subnormal
0x0020 (__FPCLASS_NEGZERO) - Negative zero
0x0040 (__FPCLASS_POSZERO) - Positive zero
0x0080 (__FPCLASS_POSSUBNORMAL) - Positive subnormal
0x0100 (__FPCLASS_POSNORMAL) - Positive normal
0x0200 (__FPCLASS_POSINF) - Positive infinity
They have corresponding builtin macros to facilitate using the builtin
function:
if (__builtin_isfpclass(x, __FPCLASS_NEGZERO | __FPCLASS_POSZERO) {
// x is any zero.
}
The data class encoding is identical to that used in llvm.is.fpclass
function.
Differential Revision: https://reviews.llvm.org/D152351
