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llvm-project/llvm/test/Transforms/GlobalOpt/assume.ll

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Assume intrinsic handling in global opt It doesn't solve the problem, when for example we load something, and then assume that it is the same as some constant value, because globalopt will fail on unknown load instruction. The proposed solution would be to skip some instructions that we can't evaluate and they are safe to skip (f.e. load, assume and many others) and see if they are required to perform optimization (f.e. we don't care about ephemeral instructions that may appear using @llvm.assume()) http://reviews.llvm.org/D12266 llvm-svn: 245919
2015-08-25 09:34:15 +08:00
; RUN: opt -S -globalopt < %s | FileCheck %s
IR: Introduce local_unnamed_addr attribute. If a local_unnamed_addr attribute is attached to a global, the address is known to be insignificant within the module. It is distinct from the existing unnamed_addr attribute in that it only describes a local property of the module rather than a global property of the symbol. This attribute is intended to be used by the code generator and LTO to allow the linker to decide whether the global needs to be in the symbol table. It is possible to exclude a global from the symbol table if three things are true: - This attribute is present on every instance of the global (which means that the normal rule that the global must have a unique address can be broken without being observable by the program by performing comparisons against the global's address) - The global has linkonce_odr linkage (which means that each linkage unit must have its own copy of the global if it requires one, and the copy in each linkage unit must be the same) - It is a constant or a function (which means that the program cannot observe that the unique-address rule has been broken by writing to the global) Although this attribute could in principle be computed from the module contents, LTO clients (i.e. linkers) will normally need to be able to compute this property as part of symbol resolution, and it would be inefficient to materialize every module just to compute it. See: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.html http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html for earlier discussion. Part of the fix for PR27553. Differential Revision: http://reviews.llvm.org/D20348 llvm-svn: 272709
2016-06-15 05:01:22 +08:00
; CHECK: @tmp = local_unnamed_addr global i32 42
Assume intrinsic handling in global opt It doesn't solve the problem, when for example we load something, and then assume that it is the same as some constant value, because globalopt will fail on unknown load instruction. The proposed solution would be to skip some instructions that we can't evaluate and they are safe to skip (f.e. load, assume and many others) and see if they are required to perform optimization (f.e. we don't care about ephemeral instructions that may appear using @llvm.assume()) http://reviews.llvm.org/D12266 llvm-svn: 245919
2015-08-25 09:34:15 +08:00
@llvm.global_ctors = appending global [1 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
@tmp = global i32 0
define i32 @TheAnswerToLifeTheUniverseAndEverything() {
ret i32 42
}
assume.ll test fixup llvm-svn: 245920
2015-08-25 09:48:49 +08:00
define void @_GLOBAL__I_a() {
Assume intrinsic handling in global opt It doesn't solve the problem, when for example we load something, and then assume that it is the same as some constant value, because globalopt will fail on unknown load instruction. The proposed solution would be to skip some instructions that we can't evaluate and they are safe to skip (f.e. load, assume and many others) and see if they are required to perform optimization (f.e. we don't care about ephemeral instructions that may appear using @llvm.assume()) http://reviews.llvm.org/D12266 llvm-svn: 245919
2015-08-25 09:34:15 +08:00
enter:
%tmp1 = call i32 @TheAnswerToLifeTheUniverseAndEverything()
store i32 %tmp1, i32* @tmp
%cmp = icmp eq i32 %tmp1, 42
call void @llvm.assume(i1 %cmp)
ret void
}
declare void @llvm.assume(i1)