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.
140 lines
5.1 KiB
LLVM
140 lines
5.1 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -S -passes=instcombine %s -o - | FileCheck %s
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target datalayout = "e-p:32:32:32-p1:64:64:64-p2:8:8:8-p3:16:16:16-p4:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:32"
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define i32 @test_as0(ptr addrspace(0) %a) {
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; CHECK-LABEL: @test_as0(
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; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i8, ptr [[A:%.*]], i32 4
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%arrayidx = getelementptr i32, ptr addrspace(0) %a, i64 1
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%y = load i32, ptr addrspace(0) %arrayidx, align 4
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ret i32 %y
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}
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define i32 @test_as1(ptr addrspace(1) %a) {
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; CHECK-LABEL: @test_as1(
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; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i8, ptr addrspace(1) [[A:%.*]], i64 4
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr addrspace(1) [[ARRAYIDX]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%arrayidx = getelementptr i32, ptr addrspace(1) %a, i32 1
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%y = load i32, ptr addrspace(1) %arrayidx, align 4
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ret i32 %y
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}
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define i32 @test_as2(ptr addrspace(2) %a) {
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; CHECK-LABEL: @test_as2(
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; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i8, ptr addrspace(2) [[A:%.*]], i8 4
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr addrspace(2) [[ARRAYIDX]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%arrayidx = getelementptr i32, ptr addrspace(2) %a, i32 1
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%y = load i32, ptr addrspace(2) %arrayidx, align 4
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ret i32 %y
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}
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define i32 @test_as3(ptr addrspace(3) %a) {
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; CHECK-LABEL: @test_as3(
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; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i8, ptr addrspace(3) [[A:%.*]], i16 4
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr addrspace(3) [[ARRAYIDX]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%arrayidx = getelementptr i32, ptr addrspace(3) %a, i32 1
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%y = load i32, ptr addrspace(3) %arrayidx, align 4
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ret i32 %y
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}
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define i32 @test_combine_ptrtoint(ptr addrspace(2) %a) {
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; CHECK-LABEL: @test_combine_ptrtoint(
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr addrspace(2) [[A:%.*]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%cast = ptrtoint ptr addrspace(2) %a to i8
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%castback = inttoptr i8 %cast to ptr addrspace(2)
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%y = load i32, ptr addrspace(2) %castback, align 4
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ret i32 %y
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}
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define i8 @test_combine_inttoptr(i8 %a) {
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; CHECK-LABEL: @test_combine_inttoptr(
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; CHECK-NEXT: ret i8 [[A:%.*]]
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;
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%cast = inttoptr i8 %a to ptr addrspace(2)
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%castback = ptrtoint ptr addrspace(2) %cast to i8
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ret i8 %castback
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}
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define i32 @test_combine_vector_ptrtoint(<2 x ptr addrspace(2)> %a) {
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; CHECK-LABEL: @test_combine_vector_ptrtoint(
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; CHECK-NEXT: [[P:%.*]] = extractelement <2 x ptr addrspace(2)> [[A:%.*]], i64 0
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; CHECK-NEXT: [[Y:%.*]] = load i32, ptr addrspace(2) [[P]], align 4
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; CHECK-NEXT: ret i32 [[Y]]
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;
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%cast = ptrtoint <2 x ptr addrspace(2)> %a to <2 x i8>
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%castback = inttoptr <2 x i8> %cast to <2 x ptr addrspace(2)>
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%p = extractelement <2 x ptr addrspace(2)> %castback, i32 0
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%y = load i32, ptr addrspace(2) %p, align 4
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ret i32 %y
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}
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define <2 x i8> @test_combine_vector_inttoptr(<2 x i8> %a) {
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; CHECK-LABEL: @test_combine_vector_inttoptr(
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; CHECK-NEXT: ret <2 x i8> [[A:%.*]]
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;
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%cast = inttoptr <2 x i8> %a to <2 x ptr addrspace(2)>
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%castback = ptrtoint <2 x ptr addrspace(2)> %cast to <2 x i8>
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ret <2 x i8> %castback
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}
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; Check that the GEP index is changed to the address space integer type (i64 -> i8)
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define ptr addrspace(2) @shrink_gep_constant_index_64_as2(ptr addrspace(2) %p) {
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; CHECK-LABEL: @shrink_gep_constant_index_64_as2(
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; CHECK-NEXT: [[RET:%.*]] = getelementptr i8, ptr addrspace(2) [[P:%.*]], i8 4
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; CHECK-NEXT: ret ptr addrspace(2) [[RET]]
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;
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%ret = getelementptr i32, ptr addrspace(2) %p, i64 1
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ret ptr addrspace(2) %ret
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}
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define ptr addrspace(2) @shrink_gep_constant_index_32_as2(ptr addrspace(2) %p) {
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; CHECK-LABEL: @shrink_gep_constant_index_32_as2(
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; CHECK-NEXT: [[RET:%.*]] = getelementptr i8, ptr addrspace(2) [[P:%.*]], i8 4
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; CHECK-NEXT: ret ptr addrspace(2) [[RET]]
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;
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%ret = getelementptr i32, ptr addrspace(2) %p, i32 1
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ret ptr addrspace(2) %ret
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}
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define ptr addrspace(3) @shrink_gep_constant_index_64_as3(ptr addrspace(3) %p) {
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; CHECK-LABEL: @shrink_gep_constant_index_64_as3(
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; CHECK-NEXT: [[RET:%.*]] = getelementptr i8, ptr addrspace(3) [[P:%.*]], i16 4
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; CHECK-NEXT: ret ptr addrspace(3) [[RET]]
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;
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%ret = getelementptr i32, ptr addrspace(3) %p, i64 1
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ret ptr addrspace(3) %ret
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}
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define ptr addrspace(2) @shrink_gep_variable_index_64_as2(ptr addrspace(2) %p, i64 %idx) {
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; CHECK-LABEL: @shrink_gep_variable_index_64_as2(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[IDX:%.*]] to i8
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; CHECK-NEXT: [[RET:%.*]] = getelementptr i32, ptr addrspace(2) [[P:%.*]], i8 [[TMP1]]
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; CHECK-NEXT: ret ptr addrspace(2) [[RET]]
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;
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%ret = getelementptr i32, ptr addrspace(2) %p, i64 %idx
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ret ptr addrspace(2) %ret
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}
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define ptr addrspace(1) @grow_gep_variable_index_8_as1(ptr addrspace(1) %p, i8 %idx) {
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; CHECK-LABEL: @grow_gep_variable_index_8_as1(
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; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[IDX:%.*]] to i64
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; CHECK-NEXT: [[RET:%.*]] = getelementptr i32, ptr addrspace(1) [[P:%.*]], i64 [[TMP1]]
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; CHECK-NEXT: ret ptr addrspace(1) [[RET]]
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;
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%ret = getelementptr i32, ptr addrspace(1) %p, i8 %idx
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ret ptr addrspace(1) %ret
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}
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