[llvm] [RISCV] Use Root instead of N throughout the worklist loop in combineBinOp_VLToVWBinOp_VL. (PR #99416)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lld-x86_64-win` running on `as-worker-93` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/146/builds/298

Here is the relevant piece of the build log for the reference:
```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/RISCV/rvv/fixed-vectors-vwmul.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
c:\a\lld-x86_64-win\build\bin\llc.exe -mtriple=riscv32 -mattr=+v -verify-machineinstrs < C:\a\lld-x86_64-win\llvm-project\llvm\test\CodeGen\RISCV\rvv\fixed-vectors-vwmul.ll | c:\a\lld-x86_64-win\build\bin\filecheck.exe C:\a\lld-x86_64-win\llvm-project\llvm\test\CodeGen\RISCV\rvv\fixed-vectors-vwmul.ll --check-prefixes=CHECK,RV32
# executed command: 'c:\a\lld-x86_64-win\build\bin\llc.exe' -mtriple=riscv32 -mattr=+v -verify-machineinstrs
# executed command: 'c:\a\lld-x86_64-win\build\bin\filecheck.exe' 'C:\a\lld-x86_64-win\llvm-project\llvm\test\CodeGen\RISCV\rvv\fixed-vectors-vwmul.ll' --check-prefixes=CHECK,RV32
# .---command stderr------------
# | C:\a\lld-x86_64-win\llvm-project\llvm\test\CodeGen\RISCV\rvv\fixed-vectors-vwmul.ll:890:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: vle8.v v8, (a1)
# |               ^
# | <stdin>:850:36: note: scanning from here
# |  vsetivli zero, 2, e16, mf4, ta, ma
# |                                    ^
# | <stdin>:851:2: note: possible intended match here
# |  vle8.v v8, (a0)
# |  ^
# | 
# | Input file: <stdin>
# | Check file: C:\a\lld-x86_64-win\llvm-project\llvm\test\CodeGen\RISCV\rvv\fixed-vectors-vwmul.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             .
# |             .
# |             .
# |           845:  .type vwmul_v2i16_multiuse, at function 
# |           846:  .variant_cc vwmul_v2i16_multiuse 
# |           847: vwmul_v2i16_multiuse: # @vwmul_v2i16_multiuse 
# |           848:  .cfi_startproc 
# |           849: # %bb.0: 
# |           850:  vsetivli zero, 2, e16, mf4, ta, ma 
# | next:890'0                                        X error: no match found
# |           851:  vle8.v v8, (a0) 
# | next:890'0     ~~~~~~~~~~~~~~~~~
# | next:890'1      ?                possible intended match
# |           852:  vle8.v v9, (a1) 
# | next:890'0     ~~~~~~~~~~~~~~~~~
# |           853:  vle8.v v10, (a2) 
# | next:890'0     ~~~~~~~~~~~~~~~~~~
# |           854:  vle8.v v11, (a3) 
# | next:890'0     ~~~~~~~~~~~~~~~~~~
# |           855:  vsext.vf2 v12, v8 
# | next:890'0     ~~~~~~~~~~~~~~~~~~~
# |           856:  vsext.vf2 v8, v9 
# | next:890'0     ~~~~~~~~~~~~~~~~~~
...

```

https://github.com/llvm/llvm-project/pull/99416