[LLVMbugs] [Bug 21672] New: r220138 caused binary size increase in Chromium

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21672

            Bug ID: 21672
           Summary: r220138 caused binary size increase in Chromium
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: hans at chromium.org
                CC: chandlerc at gmail.com, llvmbugs at cs.uiuc.edu,
                    nicolasweber at gmx.de
    Classification: Unclassified

Created attachment 13397
  --> http://llvm.org/bugs/attachment.cgi?id=13397&action=edit
Preprocessed source

(Moving this from the list:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141124/246194.html)

r220138 caused a 97 KB binary size increase in Chromium on 64-bit Linux.

Attaching preprocessed source for one TU that was significantly affected.

Build command:

 clang++ -fstack-protector --param=ssp-buffer-size=4 -fno-strict-aliasing
-fvisibility=hidden -fPIC -pthread -m64 -march=x86-64 -O2 -fno-ident
-fdata-sections -ffunction-sections -funwind-tables -fno-exceptions -fno-rtti
-fno-threadsafe-statics -fvisibility-inlines-hidden -w -std=gnu++11 -c
/tmp/ash.resize_shadow_controller.ii -o a.o

Sizes before and after your change, and at ToT:

   text    data     bss     dec     hex filename
   2626     184       0    2810     afa /tmp/220137.o
   2853     184       0    3037     bdd /tmp/220138.o
   2853     184       0    3037     bdd /tmp/222768.o


Looking at the IR diff for one of the functions that's grown (46 bytes), it's
not obvious what's going on besides some bitcasts and loads being reordered.
Looking at the asm however, it seems the loop is laid out a bit different. I'm
not sure what would cause that.

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