[Mesa-dev] RFC: PowerPC: Add Altivec vector max/min intrisics

[Adhemerval Zanella]

This patch adds the PPC Altivec instrics max/min instruction for
supported Altivec vector types (16xi8, 8xi16, 4xi32, 4xf32).

I focused my testing on the lp_test_conv, which on default behavior
expands the max/min on vectors. The lp_test_conv JIT generation
works as intended, generating vminXXX instructions instead.

Any tips, advices, comments?