90ba33099c
This patch canonicalizes getelementptr instructions with constant indices to use the `i8` source element type. This makes it easier for optimizations to recognize that two GEPs are identical, because they don't need to see past many different ways to express the same offset. This is a first step towards https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699. This is limited to constant GEPs only for now, as they have a clear canonical form, while we're not yet sure how exactly to deal with variable indices. The test llvm/test/Transforms/PhaseOrdering/switch_with_geps.ll gives two representative examples of the kind of optimization improvement we expect from this change. In the first test SimplifyCFG can now realize that all switch branches are actually the same. In the second test it can convert it into simple arithmetic. These are representative of common optimization failures we see in Rust. Fixes https://github.com/llvm/llvm-project/issues/69841.
23 lines
926 B
LLVM
23 lines
926 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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; Test to check that instcombine doesn't drop the address space when optimizing
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; memset.
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%struct.Moves = type { [9 x i8], i8, i8, i8, [5 x i8] }
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define i32 @test(ptr addrspace(1) nocapture %moves) {
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; CHECK-LABEL: define i32 @test
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; CHECK-SAME: (ptr addrspace(1) nocapture [[MOVES:%.*]]) {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr addrspace(1) [[MOVES]], i64 26
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; CHECK-NEXT: store i64 0, ptr addrspace(1) [[GEP]], align 1
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; CHECK-NEXT: ret i32 0
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;
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entry:
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%gep = getelementptr inbounds %struct.Moves, ptr addrspace(1) %moves, i32 1, i32 0, i32 9
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call void @llvm.memset.p1.i64(ptr addrspace(1) %gep, i8 0, i64 8, i1 false)
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ret i32 0
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}
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declare void @llvm.memset.p1.i64(ptr addrspace(1) nocapture, i8, i64, i1) nounwind
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