[llvm] [DenseMap] Optimize find/erase (PR #100517)

[Alexandre Ganea via llvm-commits]

aganea wrote:

Hello @MaskRay! Somehow this commit (and after) is failing one clang tests when building the Windows LLVM package:
```
C:\src\git\llvm-project>git checkout c9e5af3944e85c5f1272c48522b4e9eda398b462
Updating files: 100% (3558/3558), done.
Note: switching to 'c9e5af3944e85c5f1272c48522b4e9eda398b462'.
...
C:\src\git\llvm-project>llvm\utils\release\build_llvm_release.bat --x64 --version 19.0.0 --skip-checkout --local-python
...
-- Testing: 20961 tests, 60 workers --
Testing:
FAIL: Clang :: CodeGenObjC/gnustep2-direct-method.m (1 of 20961)
******************** TEST 'Clang :: CodeGenObjC/gnustep2-direct-method.m' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
c:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\bin\clang.exe -cc1 -internal-isystem C:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\lib\clang\20\include -nostdsysteminc -triple x86_64-unknown-freebsd -emit-llvm -fobjc-runtime=gnustep-2.2 -o - C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m | c:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\bin\filecheck.exe C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m
# executed command: 'c:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\bin\clang.exe' -cc1 -internal-isystem 'C:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\lib\clang\20\include' -nostdsysteminc -triple x86_64-unknown-freebsd -emit-llvm -fobjc-runtime=gnustep-2.2 -o - 'C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m'
# .---command stderr------------
# | C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m:3:12: warning: class 'X' defined without specifying a base class [-Wobjc-root-class]
# |     3 | @interface X
# |       |            ^
# | C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m:3:13: note: add a super class to fix this problem
# |     3 | @interface X
# |       |             ^
# | huge alignment values are unsupported
# |   %2 = load i64, ptr %1, align 9223372036854775808
# | fatal error: error in backend: Broken module found, compilation aborted!
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
# | Stack dump:
# | 0.  Program arguments: c:\\src\\git\\llvm-project\\llvm_package_19.0.0\\build64_stage0\\bin\\clang.exe -cc1 -internal-isystem C:\\src\\git\\llvm-project\\llvm_package_19.0.0\\build64_stage0\\lib\\clang\\20\\include -nostdsysteminc -triple x86_64-unknown-freebsd -emit-llvm -fobjc-runtime=gnustep-2.2 -o - C:\\src\\git\\llvm-project\\clang\\test\\CodeGenObjC\\gnustep2-direct-method.m
# | 1.  <eof> parser at end of file
# | 2.  Optimizer
# | 3.  Running pass "verify" on module "C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m"
# `-----------------------------
# error: command failed with exit status: 70
# executed command: 'c:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\bin\filecheck.exe' 'C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m'
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  c:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\bin\filecheck.exe C:\src\git\llvm-project\clang\test\CodeGenObjC\gnustep2-direct-method.m
# `-----------------------------
# error: command failed with exit status: 2

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
********************
Failed Tests (1):
  Clang :: CodeGenObjC/gnustep2-direct-method.m


Testing Time: 192.61s

Total Discovered Tests: 37881
  Skipped          :     8 (0.02%)
  Unsupported      :   300 (0.79%)
  Passed           : 37539 (99.10%)
  Expectedly Failed:    33 (0.09%)
  Failed           :     1 (0.00%)

FAILED: tools/clang/test/CMakeFiles/check-clang C:/src/git/llvm-project/llvm_package_19.0.0/build64_stage0/tools/clang/test/CMakeFiles/check-clang
C:\Windows\system32\cmd.exe /C "cd /D C:\src\git\llvm-project\llvm_package_19.0.0\build64_stage0\tools\clang\test && C:\Users\aganea_havenstudios\AppData\Local\Programs\Python\Python312\python3.exe C:/src/git/llvm-project/llvm_package_19.0.0/build64_stage0/./bin/llvm-lit.py -sv --param USE_Z3_SOLVER=0 C:/src/git/llvm-project/llvm_package_19.0.0/build64_stage0/tools/clang/test"
ninja: build stopped: subcommand failed.
```
The problem does not occur on the previous commit `4aa4ee909029cd7cd85d67b41d488a6edb802dce`.

https://github.com/llvm/llvm-project/pull/100517