[llvm-bugs] [Bug 42357] New: Regression in SVN r363875, "[LFTR] Rename variable to minimize confusion [NFC]"

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https://bugs.llvm.org/show_bug.cgi?id=42357

            Bug ID: 42357
           Summary: Regression in SVN r363875, "[LFTR] Rename variable to
                    minimize confusion [NFC]"
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: martin at martin.st
                CC: listmail at philipreames.com, llvm-bugs at lists.llvm.org

Created attachment 22130
  --> https://bugs.llvm.org/attachment.cgi?id=22130&action=edit
Reproduction C code

Since SVN r363875, "[LFTR] Rename variable to minimize confusion [NFC]",
compiling GLEW for i686 mingw almost doubled in compile time, and produces an
output almost double in size:

$ time clang-prev -target i686-w64-mingw32 -c -O3 glew-preproc-i686.c -w && ls
-lh glew-preproc-i686.o

real    1m3.655s
user    1m3.325s
sys     0m0.331s
-rw-rw-r-- 1 martin martin 615K Jun 21 21:30 glew-preproc-i686.o
$ time clang-new -target i686-w64-mingw32 -c -O3 glew-preproc-i686.c -w && ls
-lh glew-preproc-i686.o

real    1m58.397s
user    1m57.998s
sys     0m0.400s
-rw-rw-r-- 1 martin martin 1.1M Jun 21 21:33 glew-preproc-i686.o


When optimizing the output from "clang -target i686-w64-mingw32 -S -O3
glew-preproc-i686.c -Xclang -disable-llvm-passes -emit-llvm", things behave
like this:


$ time opt-old -O3 glew-preproc-i686.ll -o glew-preproc-i686.bc && ls -lh
glew-preproc-i686.bc

real    0m56.537s
user    0m56.286s
sys     0m0.253s
-rw-rw-r-- 1 martin martin 2.5M Jun 21 21:38 glew-preproc-i686.bc
$ time llc glew-preproc-i686.bc && ls -lh glew-preproc-i686.s

real    0m8.260s
user    0m8.159s
sys     0m0.100s
-rw-rw-r-- 1 martin martin 5.0M Jun 21 21:42 glew-preproc-i686.s



$ time opt-new -O3 glew-preproc-i686.ll -o glew-preproc-i686.bc && ls -lh
glew-preproc-i686.bc

real    1m19.033s
user    1m17.550s
sys     0m0.252s
-rw-rw-r-- 1 martin martin 3.8M Jun 21 21:40 glew-preproc-i686.bc
$ time llc glew-preproc-i686.bc && ls -lh glew-preproc-i686.s

real    0m37.613s
user    0m37.341s
sys     0m0.273s
-rw-rw-r-- 1 martin martin 11M Jun 21 21:45 glew-preproc-i686.s

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