[VP] Check if VP ops with functional intrinsics are speculatable

[lukel97]

Noticed whilst working on #69494. VP intrinsics whose functional equivalent is
an intrinsic were being marked as their lanes being non-speculatable, even if
the underlying intrinsic was speculatable.

This meant that

  %1 = call <4 x i32> @llvm.vp.umax(<4 x i32> %x, <4 x i32> %y, <4 x i1> %mask, i32 %evl)

would be expanded out to

  %.splatinsert = insertelement <4 x i32> poison, i32 %evl, i64 0
  %.splat = shufflevector <4 x i32> %.splatinsert, <4 x i32> poison, <4 x i32> zeroinitializer
  %1 = icmp ult <4 x i32> <i32 0, i32 1, i32 2, i32 3>, %.splat
  %2 = and <4 x i1> %1, %mask
  %3 = call <4 x i32> @llvm.umax.v4i32(<4 x i32> %x, <4 x i32> %y)

instead of

  %1 = call <4 x i32> @llvm.umax.v4i32(<4 x i32> %x, <4 x i32> %y)

The cause of this was isSafeToSpeculativelyExecuteWithOpcode checking the
function attributes for the VP instruction itself, not the functional
intrinsic. Since isSafeToSpeculativelyExecuteWithOpcode expects an already
materialized instruction, we can't use it directly for the intrinsic case. So
this fixes it by manually checking the function attributes on the intrinsic.

[RKSimon]

Please can you precommit the test changes so the patch properly shows the codegen diff

[lukel97]

Please can you precommit the test changes so the patch properly shows the codegen diff

I wanted to do that originally but expand-vp.ll is a handwritten test unfortunately. I'm tempted to convert it to update_test_checks.py, should I do that in a separate PR?

[lukel97]

Ping. Looks like the test was intentionally handwritten, with the agreement to convert it to UTC once caching had been implemented: https://reviews.llvm.org/D78203#inline-949565

[RKSimon]

LGTM