It is not correct to lower "x&(-1>>(32-y))" to "bfe x, 0, y". When y
equals 32, "-1" is not shifted, so x&(-1>>(32-32) is still x, but "bfe
x, 0, 32" is 0. However, if we know y is at most of 5 bits (< 32), we
can still do the pattern matching.

Based on the suggestion from
https://github.com/llvm/llvm-project/pull/115543, we should not do the
pattern matching from x << (32-y) >> (32-y) to "bfe x, 0, y" at all.
This reverts commits a2bacf8ab58af4c1a0247026ea131443d6066602 and
https://github.com/llvm/llvm-project/commit/bdf8e308b7ea430f619ca3aa1199a76eb6b4e2d4.

countMaxTrailingOnes() is not correct. This patch follows the suggestion
from https://github.com/llvm/llvm-project/pull/115372.

Enable pattern matching from "x<<32-y>>32-y" to "bfe x, 0, y" when we
know y is in [0,31].
This is the follow-up for the PR:
https://github.com/llvm/llvm-project/pull/114279 to fix the issue:
https://github.com/llvm/llvm-project/issues/114282

It is not correct to lower "x<<32-y>>32-y" to "bfe x, 0, y". When y
equals to 32, the left-hand side is still x (unchanged), however, the
right-hand side will be evaluated to 0. So it is not always correct to
do such transformation.

We may be able to keep the pattern for immediate y while y is within [0,
31]. However, the immediate operands of the sub (32 - y) are easily
folded, and "(x << imm) >> imm" will be lowered to "and x,
(2^(32-imm))-1" anyway. So no bfe matching is needed.

The issue is uncovered by #47698: for IR files without a target triple,
-mtriple= specifies the full target triple while -march= merely sets the
architecture part of the default target triple, leaving a target triple which
may not make sense, e.g. riscv64-apple-darwin.

Therefore, -march= is error-prone and not recommended for tests without a target
triple. The issue has been benign as we recognize $unknown-apple-darwin as ELF instead
of rejecting it outrightly.

Change VOP_PAT_GEN to default to not generating an instruction selection
pattern for the VOP2 (e32) form of an instruction, only for the VOP3
(e64) form. This allows SIFoldOperands maximum freedom to fold copies
into the operands of an instruction, before SIShrinkInstructions tries
to shrink it back to the smaller encoding.

This affects the following VOP2 instructions:
v_min_i32
v_max_i32
v_min_u32
v_max_u32
v_and_b32
v_or_b32
v_xor_b32
v_lshr_b32
v_ashr_i32
v_lshl_b32

A further cleanup could simplify or remove VOP_PAT_GEN, since its
optional second argument is never used.

Differential Revision: https://reviews.llvm.org/D114252

The existing constrained shift PatFrags only dealt with masked shift
from OpenCL front-ends. This change copies the
X86DAGToDAGISel::isUnneededShiftMask() function to AMDGPU and uses it in
the shift PatFrag predicates.

Differential Revision: https://reviews.llvm.org/D113448

Differential Revision: https://reviews.llvm.org/D73483

Reviewers: rampitec