[llvm] LAA: handle 0 return from getPtrStride correctly (PR #124539)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-out-of-tree` running on `linaro-flang-aarch64-out-of-tree` while building `llvm` at step 7 "build-flang-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/53/builds/11391

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

```
Step 7 (build-flang-unified-tree) failure: build (failure)
...
110.196 [9/7/21] Generating ../../include/flang/__cuda_builtins.mod
110.196 [9/6/22] Generating ../../include/flang/__ppc_types.mod
110.304 [9/5/23] Generating ../../include/flang/ieee_arithmetic.mod
110.315 [9/4/24] Generating ../../include/flang/iso_c_binding.mod
110.324 [9/3/25] Generating ../../include/flang/ieee_exceptions.mod
113.884 [9/2/26] Generating ../../include/flang/iso_fortran_env_impl.mod, iso_fortran_env_impl.o
114.111 [8/2/27] Generating ../../include/flang/__cuda_device.mod
114.216 [7/2/28] Generating ../../include/flang/iso_fortran_env.mod
114.313 [6/2/29] Generating ../../include/flang/cudadevice.mod
114.628 [5/2/30] Building CXX object runtime/CMakeFiles/FortranRuntime.dir/exceptions.cpp.o
FAILED: runtime/CMakeFiles/FortranRuntime.dir/exceptions.cpp.o 
/usr/local/bin/c++ -DFLANG_INCLUDE_TESTS=1 -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_flang/runtime -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang/runtime -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang/include -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_flang/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/mlir/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_llvm/tools/mlir/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/llvm/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_llvm/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/clang/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_llvm/tools/clang/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Werror -Wno-deprecated-copy -Wno-string-conversion -Wno-ctad-maybe-unsupported -Wno-unused-command-line-argument -Wstring-conversion           -Wcovered-switch-default -Wno-nested-anon-types -fno-lto -O3 -DNDEBUG -std=c++17   -D_GNU_SOURCE -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -U_GLIBCXX_ASSERTIONS -U_LIBCPP_ENABLE_ASSERTIONS -UNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -MD -MT runtime/CMakeFiles/FortranRuntime.dir/exceptions.cpp.o -MF runtime/CMakeFiles/FortranRuntime.dir/exceptions.cpp.o.d -o runtime/CMakeFiles/FortranRuntime.dir/exceptions.cpp.o -c /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang/runtime/exceptions.cpp
../llvm-project/flang/runtime/exceptions.cpp:111:14: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
  111 |   _FPU_GETCW(fpcr);
      |              ^
../llvm-project/flang/runtime/exceptions.cpp:111:3: note: use constraint modifier "w"
  111 |   _FPU_GETCW(fpcr);
      |   ^
/usr/include/aarch64-linux-gnu/fpu_control.h:33:30: note: expanded from macro '_FPU_GETCW'
   33 |   __asm__ __volatile__ ("mrs    %0, fpcr" : "=r" (fpcr))
      |                                 ^
../llvm-project/flang/runtime/exceptions.cpp:122:14: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
  122 |   _FPU_GETCW(fpcr);
      |              ^
../llvm-project/flang/runtime/exceptions.cpp:122:3: note: use constraint modifier "w"
  122 |   _FPU_GETCW(fpcr);
      |   ^
/usr/include/aarch64-linux-gnu/fpu_control.h:33:30: note: expanded from macro '_FPU_GETCW'
   33 |   __asm__ __volatile__ ("mrs    %0, fpcr" : "=r" (fpcr))
      |                                 ^
../llvm-project/flang/runtime/exceptions.cpp:128:14: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
  128 |   _FPU_SETCW(fpcr);
      |              ^
../llvm-project/flang/runtime/exceptions.cpp:128:3: note: use constraint modifier "w"
  128 |   _FPU_SETCW(fpcr);
      |   ^
/usr/include/aarch64-linux-gnu/fpu_control.h:36:36: note: expanded from macro '_FPU_SETCW'
   36 |   __asm__ __volatile__ ("msr    fpcr, %0" : : "r" (fpcr))
      |                                       ^
3 errors generated.
162.375 [5/1/31] Building CXX object tools/bbc/CMakeFiles/bbc.dir/bbc.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/124539