[CAS] Fix alignment error from MappedFileRegionArena

[cachemeifyoucan]

Fix a bug that when an alignment error can happen when reading a slice
of file from existing MappedFileRegionArena.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder sanitizer-x86_64-linux running on sanitizer-buildbot1 while building llvm at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/19264

Here is the relevant piece of the build log for the reference

Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure)
...
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:248: warning: COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=ON, but this test suite does not support testing the just-built runtime libraries when the test compiler is configured to use different runtime libraries. Either modify this test suite to support this test configuration, or set COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=OFF to test the runtime libraries included in the compiler instead.
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:259: note: Testing using libraries in "/home/b/sanitizer-x86_64-linux/build/build_default/./lib/../lib/clang/22/lib/i386-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:237: warning: Compiler lib dir != compiler-rt lib dir
Compiler libdir:     "/home/b/sanitizer-x86_64-linux/build/build_default/lib/clang/22/lib/i386-unknown-linux-gnu"
compiler-rt libdir:  "/home/b/sanitizer-x86_64-linux/build/build_default/lib/clang/22/lib/x86_64-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:248: warning: COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=ON, but this test suite does not support testing the just-built runtime libraries when the test compiler is configured to use different runtime libraries. Either modify this test suite to support this test configuration, or set COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=OFF to test the runtime libraries included in the compiler instead.
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:259: note: Testing using libraries in "/home/b/sanitizer-x86_64-linux/build/build_default/./lib/../lib/clang/22/lib/x86_64-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/llvm/utils/lit/lit/main.py:74: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 900 seconds was requested on the command line. Forcing timeout to be 900 seconds.
-- Testing: 10410 tests, 64 workers --
Testing:  0.. 10.. 20.. 
FAIL: LeakSanitizer-AddressSanitizer-i386 :: TestCases/use_globals_uninitialized.cpp (3297 of 10410)
******************** TEST 'LeakSanitizer-AddressSanitizer-i386 :: TestCases/use_globals_uninitialized.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang  --driver-mode=g++ -O0  -m32  -gline-tables-only -fsanitize=address -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/../ /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp # RUN: at line 2
+ /home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang --driver-mode=g++ -O0 -m32 -gline-tables-only -fsanitize=address -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/../ /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp
env LSAN_OPTIONS=:detect_leaks=1:"report_objects=1:use_stacks=0:use_registers=0:use_globals=0" not  /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp 2>&1 | FileCheck /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp # RUN: at line 3
+ FileCheck /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp
+ env LSAN_OPTIONS=:detect_leaks=1:report_objects=1:use_stacks=0:use_registers=0:use_globals=0 not /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp
/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp:20:11: error: CHECK: expected string not found in input
// CHECK: [[ADDR]] (1337 bytes)
          ^
<stdin>:4:55: note: scanning from here
==1745086==ERROR: LeakSanitizer: detected memory leaks
                                                      ^
<stdin>:4:55: note: with "ADDR" equal to "0xec703680"
==1745086==ERROR: LeakSanitizer: detected memory leaks
                                                      ^
<stdin>:19:10: note: possible intended match here
0xecd00700 (32 bytes)
         ^

Input file: <stdin>
Check file: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
            1: Test alloc: 0xec703680  
            2:  
            3: ================================================================= 
            4: ==1745086==ERROR: LeakSanitizer: detected memory leaks 
check:20'0                                                           X error: no match found
check:20'1                                                             with "ADDR" equal to "0xec703680"
            5:  
check:20'0     ~
Step 9 (test compiler-rt symbolizer) failure: test compiler-rt symbolizer (failure)
...
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:248: warning: COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=ON, but this test suite does not support testing the just-built runtime libraries when the test compiler is configured to use different runtime libraries. Either modify this test suite to support this test configuration, or set COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=OFF to test the runtime libraries included in the compiler instead.
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:259: note: Testing using libraries in "/home/b/sanitizer-x86_64-linux/build/build_default/./lib/../lib/clang/22/lib/i386-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:237: warning: Compiler lib dir != compiler-rt lib dir
Compiler libdir:     "/home/b/sanitizer-x86_64-linux/build/build_default/lib/clang/22/lib/i386-unknown-linux-gnu"
compiler-rt libdir:  "/home/b/sanitizer-x86_64-linux/build/build_default/lib/clang/22/lib/x86_64-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:248: warning: COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=ON, but this test suite does not support testing the just-built runtime libraries when the test compiler is configured to use different runtime libraries. Either modify this test suite to support this test configuration, or set COMPILER_RT_TEST_STANDALONE_BUILD_LIBS=OFF to test the runtime libraries included in the compiler instead.
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lit.common.cfg.py:259: note: Testing using libraries in "/home/b/sanitizer-x86_64-linux/build/build_default/./lib/../lib/clang/22/lib/x86_64-unknown-linux-gnu"
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/llvm/utils/lit/lit/main.py:74: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 900 seconds was requested on the command line. Forcing timeout to be 900 seconds.
-- Testing: 10410 tests, 64 workers --
Testing:  0.. 10.. 20.. 
FAIL: LeakSanitizer-AddressSanitizer-i386 :: TestCases/use_globals_uninitialized.cpp (3297 of 10410)
******************** TEST 'LeakSanitizer-AddressSanitizer-i386 :: TestCases/use_globals_uninitialized.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang  --driver-mode=g++ -O0  -m32  -gline-tables-only -fsanitize=address -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/../ /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp # RUN: at line 2
+ /home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang --driver-mode=g++ -O0 -m32 -gline-tables-only -fsanitize=address -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/../ /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp
env LSAN_OPTIONS=:detect_leaks=1:"report_objects=1:use_stacks=0:use_registers=0:use_globals=0" not  /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp 2>&1 | FileCheck /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp # RUN: at line 3
+ FileCheck /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp
+ env LSAN_OPTIONS=:detect_leaks=1:report_objects=1:use_stacks=0:use_registers=0:use_globals=0 not /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/lsan/I386AsanConfig/TestCases/Output/use_globals_uninitialized.cpp.tmp
/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp:20:11: error: CHECK: expected string not found in input
// CHECK: [[ADDR]] (1337 bytes)
          ^
<stdin>:4:55: note: scanning from here
==1745086==ERROR: LeakSanitizer: detected memory leaks
                                                      ^
<stdin>:4:55: note: with "ADDR" equal to "0xec703680"
==1745086==ERROR: LeakSanitizer: detected memory leaks
                                                      ^
<stdin>:19:10: note: possible intended match here
0xecd00700 (32 bytes)
         ^

Input file: <stdin>
Check file: /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/lsan/TestCases/use_globals_uninitialized.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
            1: Test alloc: 0xec703680  
            2:  
            3: ================================================================= 
            4: ==1745086==ERROR: LeakSanitizer: detected memory leaks 
check:20'0                                                           X error: no match found
check:20'1                                                             with "ADDR" equal to "0xec703680"
            5:  
check:20'0     ~

[DavidSpickett]

That fixed it, re-enabled Arm in #159302.

You were right then, GCC must have emitted a more permissive instruction.