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[FunctionAttrs] Incorrect nonnull inference for non-inbounds GEP #91177

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nikic opened this issue May 6, 2024 · 2 comments · Fixed by #91180
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[FunctionAttrs] Incorrect nonnull inference for non-inbounds GEP #91177

nikic opened this issue May 6, 2024 · 2 comments · Fixed by #91180
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@nikic
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ipo Interprocedural optimizations miscompilation
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LLVM 18.X Release

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@nikic
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nikic commented May 6, 2024

FunctionAttrs incorrectly infers that the following function returns nonnull (https://llvm.godbolt.org/z/49Kbq15xn):

define ptr @test(ptr nonnull %arg) {
  %res = getelementptr i8, ptr %arg, i64 -8
  ret ptr %res
}

This is because the code assumes that the result of a GEP is non-null if the source is non-null here:

llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp

Line 1189 in d98a785

case Instruction::GetElementPtr:
This is not correct for non-inbounds GEPs.
@nikic nikic self-assigned this May 6, 2024
@nikic nikic mentioned this issue May 6, 2024
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@nikic nikic added this to the LLVM 18.X Release milestone May 6, 2024
@github-project-automation github-project-automation bot moved this to Needs Triage in LLVM Release Status May 6, 2024
nikic added a commit to nikic/llvm-project that referenced this issue May 6, 2024
@nikic
[FunctionAttrs] Add test for llvm#91177 (NFC)
a53cc13
nikic added a commit to nikic/llvm-project that referenced this issue May 6, 2024
@nikic
[FunctionAttrs] Fix incorrect nonnull inference for non-inbounds GEP
a38222c 
For inbounds GEPs, if the source pointer is non-null, the result
must also be non-null. However, this does not hold for non-inbounds
GEPs.

Fixes llvm#91177.
@nikic nikic mentioned this issue May 6, 2024
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nikic added a commit that referenced this issue May 7, 2024
@nikic
[FunctionAttrs] Fix incorrect nonnull inference for non-inbounds GEP (#…
f34d30c 
…91180)

For inbounds GEPs, if the source pointer is non-null, the result must
also be non-null. However, this does not hold for non-inbounds GEPs.
    
Fixes #91177.
@github-project-automation github-project-automation bot moved this from Needs Triage to Done in LLVM Release Status May 7, 2024
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nikic commented May 7, 2024

/cherry-pick f34d30c

llvmbot pushed a commit to llvmbot/llvm-project that referenced this issue May 7, 2024
@nikic @llvmbot
[FunctionAttrs] Fix incorrect nonnull inference for non-inbounds GEP (l…
f52cdf6 
…lvm#91180)

For inbounds GEPs, if the source pointer is non-null, the result must
also be non-null. However, this does not hold for non-inbounds GEPs.

Fixes llvm#91177.

(cherry picked from commit f34d30c)
@llvmbot
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llvmbot commented May 7, 2024

/pull-request #91286

@EugeneZelenko EugeneZelenko added ipo Interprocedural optimizations and removed llvm:optimizations labels May 7, 2024
tstellar pushed a commit to llvmbot/llvm-project that referenced this issue May 9, 2024
@nikic @tstellar
[FunctionAttrs] Fix incorrect nonnull inference for non-inbounds GEP (l…
4a28f8e 
…lvm#91180)

For inbounds GEPs, if the source pointer is non-null, the result must
also be non-null. However, this does not hold for non-inbounds GEPs.

Fixes llvm#91177.

(cherry picked from commit f34d30c)
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ipo Interprocedural optimizations miscompilation
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LLVM Release Status
Status: Done
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LLVM 18.X Release
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[FunctionAttrs] Fix incorrect nonnull inference for non-inbounds GEP nikic/llvm-project
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@nikic @EugeneZelenko @llvmbot