[llvm-bugs] [Bug 47242] New: missed instruction sink across asm goto

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47242

            Bug ID: 47242
           Summary: missed instruction sink across asm goto
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ndesaulniers at google.com
                CC: blitzrakete at gmail.com, craig.topper at gmail.com,
                    dgregor at apple.com, erik.pilkington at gmail.com,
                    isanbard at gmail.com, jyknight at google.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk
            Blocks: 4068

I was looking at a bug report against GCC 8
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90193), and noticed our codegen
could be improved: https://godbolt.org/z/zqK1K7.  I was wondering if we could
sink the zeroing of the return register after the asm statement, so that we're
avoiding a dead write along one of the branches?


Referenced Bugs:

https://bugs.llvm.org/show_bug.cgi?id=4068
[Bug 4068] [Meta] Compiling the Linux kernel with clang
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