https://llvm.org/bugs/show_bug.cgi?id=30597
Bug ID: 30597
Summary: instcombine drops load !nonnull metadata on an
inttoptr/ptrtoint
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: arie...@mail.tau.ac.il
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
## Description
When instcombine simplifies a inttoptr/ptrtoint pair that covers a load,
!nonnull metadata on the load seems to be dropped on the floor, leading to
missed optimizations.
This is one of the causes of https://github.com/rust-lang/rust/issues/36920
(the current version of rustc does not emit the required nonnull metadata, but
modifying it to emit the metadata leads to this issue).
Tested on Rust's fork of LLVM 3.9 and Debian's LLVM 3.7.
## STR
; ModuleID = 'test.cgu-0.rs'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: readonly uwtable
define i32 @dot_ref_s(i32** noalias nocapture readonly dereferenceable(8)) {
entry-block:
%loadedptr = load i32*, i32** %0, align 8, !nonnull !0
%ptrtoint = ptrtoint i32* %loadedptr to i64
%inttoptr = inttoptr i64 %ptrtoint to i32*
%switchtmp = icmp eq i32* %inttoptr, null
br i1 %switchtmp, label %bb6, label %bb7
bb6:
ret i32 0
bb7:
ret i32 42
}
!0 = !{}
## Expected Result
The null check is optimized out.
## Actual Result
; ModuleID = '<stdin>'
source_filename = "test.cgu-0.rs"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i32 @dot_ref_s(i32** noalias nocapture readonly dereferenceable(8)) {
entry-block:
%loadedptr12 = load i32*, i32** %0, align 8 ; <- where is my metadata?
%switchtmp = icmp eq i32* %loadedptr12, null
br i1 %switchtmp, label %bb6, label %bb7
bb6: ; preds = %entry-block
ret i32 0
bb7: ; preds = %entry-block
ret i32 42
}
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