[NFC] Update vec_extract builtin signatures to take signed int.

[amyk]

Summary

This patch updates the vec_extract builtins to take a signed int as the second
parameter, as defined by the Power Vector Intrinsics Programming Reference.
This patch is NFC and all existing tests pass.

[quinnp]

lgtm

[NeHuang]

LTGM

clang/lib/Headers/altivec.h

 }
 #endif
 
 /* ------------------------ extensions for CBEA ----------------------------- */
 
 /* vec_extract */
 
 static __inline__ signed char __ATTRS_o_ai vec_extract(vector signed char __a,
-                                                       unsigned int __b) {
+                                                       signed int __b) {
   return __a[__b & 0xf];
 }
 
 static __inline__ unsigned char __ATTRS_o_ai
-vec_extract(vector unsigned char __a, unsigned int __b) {
+vec_extract(vector unsigned char __a, signed int __b) {
   return __a[__b & 0xf];
 }
 
 static __inline__ unsigned char __ATTRS_o_ai vec_extract(vector bool char __a,
-                                                         unsigned int __b) {
+                                                         signed int __b) {
   return __a[__b & 0xf];
 }
 
 static __inline__ signed short __ATTRS_o_ai vec_extract(vector signed short __a,
-                                                        unsigned int __b) {
+                                                        signed int __b) {
   return __a[__b & 0x7];
 }
 
 static __inline__ unsigned short __ATTRS_o_ai
-vec_extract(vector unsigned short __a, unsigned int __b) {
+vec_extract(vector unsigned short __a, signed int __b) {
   return __a[__b & 0x7];
 }
 
 static __inline__ unsigned short __ATTRS_o_ai vec_extract(vector bool short __a,
-                                                          unsigned int __b) {
+                                                          signed int __b) {
   return __a[__b & 0x7];
 }
 
 static __inline__ signed int __ATTRS_o_ai vec_extract(vector signed int __a,
-                                                      unsigned int __b) {
+                                                      signed int __b) {
   return __a[__b & 0x3];
 }
 
 static __inline__ unsigned int __ATTRS_o_ai vec_extract(vector unsigned int __a,
-                                                        unsigned int __b) {
+                                                        signed int __b) {
   return __a[__b & 0x3];
 }
 
 static __inline__ unsigned int __ATTRS_o_ai vec_extract(vector bool int __a,
-                                                        unsigned int __b) {
+                                                        signed int __b) {
   return __a[__b & 0x3];
 }
 
 #ifdef __VSX__
 static __inline__ signed long long __ATTRS_o_ai
-vec_extract(vector signed long long __a, unsigned int __b) {
+vec_extract(vector signed long long __a, signed int __b) {
   return __a[__b & 0x1];
 }
 
 static __inline__ unsigned long long __ATTRS_o_ai
-vec_extract(vector unsigned long long __a, unsigned int __b) {
+vec_extract(vector unsigned long long __a, signed int __b) {
   return __a[__b & 0x1];
 }
 
 static __inline__ unsigned long long __ATTRS_o_ai
-vec_extract(vector bool long long __a, unsigned int __b) {
+vec_extract(vector bool long long __a, signed int __b) {
   return __a[__b & 0x1];
 }
 
 static __inline__ double __ATTRS_o_ai vec_extract(vector double __a,
-                                                  unsigned int __b) {
+                                                  signed int __b) {
   return __a[__b & 0x1];
 }
 #endif
 
 static __inline__ float __ATTRS_o_ai vec_extract(vector float __a,
-                                                 unsigned int __b) {
+                                                 signed int __b) {
   return __a[__b & 0x3];
 }
 
 #ifdef __POWER9_VECTOR__
 
 #define vec_insert4b __builtin_vsx_insertword
 #define vec_extract4b __builtin_vsx_extractuword