https://llvm.org/bugs/show_bug.cgi?id=30216
Bug ID: 30216
Summary: GVNHoist hoists a store above a load of the same
memory location
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: seb...@gmail.com
Reporter: george.burgess...@gmail.com
CC: dber...@dberlin.org, llvm-bugs@lists.llvm.org
Classification: Unclassified
Hi! I have a repro of a bug for you (on r280192):
$ echo '
@A = external global i8
@B = external global i8*
define i8* @Foo() {
store i8 0, i8* @A
br i1 undef, label %if.then, label %if.else
if.then:
store i8* null, i8** @B
ret i8* null
if.else:
%1 = load i8*, i8** @B
store i8* null, i8** @B
ret i8* %1
}
' | opt -gvn-hoist -S
@A = external global i8
@B = external global i8*
define i8* @Foo() {
store i8 0, i8* @A
store i8* null, i8** @B
br i1 undef, label %if.then, label %if.else
if.then: ; preds = %0
ret i8* null
if.else: ; preds = %0
%1 = load i8*, i8** @B
ret i8* %1
}
The hoist of the store to @B above a load of @B is illegal. This won't repro
without the store to @A at the top. :)
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