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missed bitcast optimization #1635

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llvmbot opened this issue Mar 21, 2007 · 5 comments
Closed

missed bitcast optimization #1635

llvmbot opened this issue Mar 21, 2007 · 5 comments
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bugzilla Issues migrated from bugzilla code-quality

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@llvmbot
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llvmbot commented Mar 21, 2007

Bugzilla Link 1263
Resolution FIXED
Resolved on Feb 22, 2010 12:51
Version 1.0
OS All
Attachments Small but not completely reduced testcase
Reporter LLVM Bugzilla Contributor

Extended Description

In the attached .ll you can find:
%tmp64 = bitcast i32* %tmp1 to { i32 }* ; <{ i32 }> [#uses=1]
%tmp65 = getelementptr { i32 } %tmp64, i32 0, i32 0 ;
<i32*> [#uses=1]
Thus %tmp65 is equal to %tmp1, but the optimizers miss this. This strange
construction was produced by llvm-convert, or so it seems. I will try to
find out why it is being produced in the first place.
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llvmbot commented Mar 21, 2007

assigned to @lattner

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lattner commented Mar 25, 2007

Nice catch. Testcase here: Transforms/InstCombine/cast2.ll:test3

Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070319/046249.html

-Chris

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llvmbot commented Mar 29, 2007

Actually, this could be more general: trailing zeros can be eliminated,
at least if all indices are constant. For example, indices "1,0" could
be turned into "1" plus a bitcast.

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lattner commented Mar 29, 2007

Of course. Again, the goal isn't to reimplement instcombine :)

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llvmbot commented Nov 27, 2021

mentioned in issue llvm/llvm-bugzilla-archive#5167

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
troelsbjerre pushed a commit to troelsbjerre/llvm-project that referenced this issue Jan 10, 2024
@fredriss
Merge pull request llvm#1635 from JDevlieghere/🍒/bastille/254e0abf5be…
b3eb9ff 
…2e98cb7f1fa52617b71f4b94b11a4

[lldb] Fix the last remaining tests not inheriting TCC permissions
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