[llvm] [AMDGPU] Do not use original PHIs in coercion chains (PR #98063)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-dylib` running on `linaro-flang-aarch64-dylib` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/50/builds/938

Here is the relevant piece of the build log for the reference:
```
Step 5 (build-unified-tree) failure: build (failure)
...
48.128 [3335/4/3226] Copying clang's avx512vpopcntdqintrin.h...
48.134 [3335/3/3227] Copying clang's avx512vpopcntdqvlintrin.h...
48.163 [3329/8/3228] Linking CXX static library lib/libLLVMLTO.a
48.164 [3329/7/3229] Copying clang's avxifmaintrin.h...
48.164 [3329/6/3230] Copying clang's avxintrin.h...
48.164 [3329/5/3231] Copying clang's avxneconvertintrin.h...
48.165 [3329/4/3232] Copying clang's avxvnniint16intrin.h...
48.165 [3329/3/3233] Copying clang's avxvnniint8intrin.h...
48.170 [3329/2/3234] Copying clang's avxvnniintrin.h...
52.551 [3329/1/3235] Building CXX object tools/flang/lib/Optimizer/Dialect/CUF/CMakeFiles/obj.CUFDialect.dir/CUFOps.cpp.o
FAILED: tools/flang/lib/Optimizer/Dialect/CUF/CMakeFiles/obj.CUFDialect.dir/CUFOps.cpp.o 
/usr/local/bin/c++ -DFLANG_INCLUDE_TESTS=1 -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/flang/lib/Optimizer/Dialect/CUF -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/flang/lib/Optimizer/Dialect/CUF -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/flang/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/flang/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/build/include -I/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/llvm/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/llvm/../mlir/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/mlir/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/tools/clang/include -isystem /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/llvm/../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 -Wno-deprecated-copy -Wno-string-conversion -Wno-ctad-maybe-unsupported -Wno-unused-command-line-argument -Wstring-conversion           -Wcovered-switch-default -Wno-nested-anon-types -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT tools/flang/lib/Optimizer/Dialect/CUF/CMakeFiles/obj.CUFDialect.dir/CUFOps.cpp.o -MF tools/flang/lib/Optimizer/Dialect/CUF/CMakeFiles/obj.CUFDialect.dir/CUFOps.cpp.o.d -o tools/flang/lib/Optimizer/Dialect/CUF/CMakeFiles/obj.CUFDialect.dir/CUFOps.cpp.o -c /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/flang/lib/Optimizer/Dialect/CUF/CUFOps.cpp
In file included from /home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/flang/lib/Optimizer/Dialect/CUF/CUFOps.cpp:16:
/home/tcwg-buildbot/worker/flang-aarch64-dylib/llvm-project/flang/include/flang/Optimizer/Dialect/FIRAttr.h:162:10: fatal error: 'flang/Optimizer/Dialect/FIREnumAttr.h.inc' file not found
  162 | #include "flang/Optimizer/Dialect/FIREnumAttr.h.inc"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
ninja: build stopped: subcommand failed.

```

https://github.com/llvm/llvm-project/pull/98063