[llvm] [GlobalISel] Add computeNumSignBits for SHL (PR #152067)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `cross-project-tests-sie-ubuntu` running on `doug-worker-1a` while building `llvm` at step 6 "test-build-unified-tree-check-cross-project".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/181/builds/27670

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-cross-project) failure: test (failure)
******************** TEST 'cross-project-tests :: debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
optnone-vectors-and-functions.cpp: (1.0000)

## BEGIN ##
.   [0, "int vector[4] test1<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 30, 11, "StopReason.BREAKPOINT", "StepKind.FUNC", []]
.   [1, "int vector[4] test1<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 31, 12, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [2, "int vector[4] test1<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 32, 10, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [3, "int vector[4] test2<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 59, 7, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [4, "int vector[4] test2<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 61, 9, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [5, "int vector[4] test2<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 62, 12, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [6, "int vector[4] test2<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 65, 14, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [7, "int vector[4] test2<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 66, 10, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [8, "int vector[4] test3<int vector[4]>(int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 93, 23, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [9, "int vector[4] test3<int vector[4]>(int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 94, 10, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [10, "int vector[4] test4<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 110, 13, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
.   [11, "int vector[4] test4<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 110, 13, "StopReason.BREAKPOINT", "StepKind.SAME", []]
.   [12, "int vector[4] test4<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 110, 13, "StopReason.BREAKPOINT", "StepKind.SAME", []]
.   [13, "int vector[4] test4<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 110, 13, "StopReason.BREAKPOINT", "StepKind.SAME", []]
.   [14, "int vector[4] test4<int vector[4]>(int vector[4], int vector[4])", "/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu/llvm-project/cross-project-tests/debuginfo-tests/dexter-tests/optnone-vectors-and-functions.cpp", 111, 10, "StopReason.BREAKPOINT", "StepKind.VERTICAL_FORWARD", []]
## END (15 steps) ##


  optnone-vectors-and-functions.cpp:110 [i] ExpectValue [0/21]
    expected encountered watches:
      0
      1
      2
      3

  optnone-vectors-and-functions.cpp:110-111 [x[0]] ExpectValue [0/14]
    expected encountered watches:
      1
      8

  optnone-vectors-and-functions.cpp:110-111 [x[1]] ExpectValue [0/14]
    expected encountered watches:
      2
      9

  optnone-vectors-and-functions.cpp:110-111 [x[2]] ExpectValue [0/14]
    expected encountered watches:
      10
      3

  optnone-vectors-and-functions.cpp:110-111 [x[3]] ExpectValue [0/14]
    expected encountered watches:
...

```

</details>

https://github.com/llvm/llvm-project/pull/152067