amehsan added inline comments.
================
Comment at: lib/Headers/altivec.h:350
+ __tempc = __tempc & 0x00000001;
+ unsigned long long __longa = (unsigned long long) __tempa;
+ unsigned long long __longb = (unsigned long long) __tempb;
----------------
kbarton wrote:
> nemanjai wrote:
> > I think it's a little more clear and obvious what is happening if you
> > actually have just a single cast and mask - i.e.
> > ``` unsigned long long __longa = ((unsigned long long) __a[i]) &
> > 0xFFFFFFFF;```
> Is a mask actually needed? This seems to be what is done in the vec_addec
> function below, without the cast. I agree that is cleaner.
>
> The other minor nit is to pick a single value for the mask (1, 0x01,
> 0x00000001) and use it consistently.
To come up with this code pattern I looked at the following pieces of codes:
```
unsigned long long f (int t) {
return (unsigned long long) t;
}
```
When compiled with optimization produces
```
define i64 @f(i32 signext %t) local_unnamed_addr #0 {
entry:
%conv = sext i32 %t to i64
ret i64 %conv
}
```
Which is incorrect. Also
```
unsigned long long f (int t) {
return (unsigned long long)(unsigned) t;
}
~
```
results in
```
define i64 @f(i32 signext %t) local_unnamed_addr #0 {
entry:
%conv = zext i32 %t to i64
ret i64 %conv
}
```
and
```
.Lfunc_begin0:
# BB#0: # %entry
clrldi 3, 3, 32
blr
```
So I think the code here is optimal and correct and there is no need to change
it.
================
Comment at: lib/Headers/altivec.h:10516
+ vector signed __int128 __c) {
+ return __builtin_altivec_vsubecuq(__a, __b, __c);
+}
----------------
kbarton wrote:
> Why do we mask the carries for sign/unsigned ints, but not __128 ints?
for quadword, hardware does the masking (implicitly, by only looking at the
rightmost bit)
https://reviews.llvm.org/D26544
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