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.
97 lines
4.9 KiB
LLVM
97 lines
4.9 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -passes="default<O1>" -S < %s | FileCheck --check-prefixes=O1 %s
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; RUN: opt -passes="default<O2>" -S < %s | FileCheck --check-prefixes=O23 %s
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; RUN: opt -passes="default<O3>" -S < %s | FileCheck --check-prefixes=O23 %s
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; We should retain the TBAA on the load here, not lose it.
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define void @licm(ptr align 8 dereferenceable(8) %_M_start.i, i64 %numElem) {
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; O1-LABEL: @licm(
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; O1-NEXT: entry:
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; O1-NEXT: [[CMP1_NOT:%.*]] = icmp eq i64 [[NUMELEM:%.*]], 0
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; O1-NEXT: br i1 [[CMP1_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_LR_PH:%.*]]
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; O1: for.body.lr.ph:
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; O1-NEXT: [[TMP0:%.*]] = load ptr, ptr [[_M_START_I:%.*]], align 8, !tbaa [[TBAA3:![0-9]+]]
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; O1-NEXT: br label [[FOR_BODY:%.*]]
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; O1: for.body:
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; O1-NEXT: [[K_02:%.*]] = phi i64 [ 0, [[FOR_BODY_LR_PH]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
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; O1-NEXT: [[ADD_PTR_I:%.*]] = getelementptr inbounds double, ptr [[TMP0]], i64 [[K_02]]
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; O1-NEXT: store double 2.000000e+00, ptr [[ADD_PTR_I]], align 8, !tbaa [[TBAA8:![0-9]+]]
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; O1-NEXT: [[INC]] = add nuw i64 [[K_02]], 1
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; O1-NEXT: [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INC]], [[NUMELEM]]
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; O1-NEXT: br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]]
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; O1: for.cond.cleanup:
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; O1-NEXT: ret void
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;
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; O23-LABEL: @licm(
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; O23-NEXT: entry:
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; O23-NEXT: [[CMP1_NOT:%.*]] = icmp eq i64 [[NUMELEM:%.*]], 0
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; O23-NEXT: br i1 [[CMP1_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_LR_PH:%.*]]
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; O23: for.body.lr.ph:
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; O23-NEXT: [[TMP0:%.*]] = load ptr, ptr [[_M_START_I:%.*]], align 8, !tbaa [[TBAA3:![0-9]+]]
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; O23-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[NUMELEM]], 4
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; O23-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[FOR_BODY_PREHEADER:%.*]], label [[VECTOR_PH:%.*]]
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; O23: vector.ph:
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; O23-NEXT: [[N_VEC:%.*]] = and i64 [[NUMELEM]], -4
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; O23-NEXT: br label [[VECTOR_BODY:%.*]]
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; O23: vector.body:
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; O23-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
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; O23-NEXT: [[TMP1:%.*]] = getelementptr inbounds double, ptr [[TMP0]], i64 [[INDEX]]
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; O23-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[TMP1]], i64 16
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; O23-NEXT: store <2 x double> <double 2.000000e+00, double 2.000000e+00>, ptr [[TMP1]], align 8, !tbaa [[TBAA8:![0-9]+]]
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; O23-NEXT: store <2 x double> <double 2.000000e+00, double 2.000000e+00>, ptr [[TMP2]], align 8, !tbaa [[TBAA8]]
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; O23-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
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; O23-NEXT: [[TMP3:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
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; O23-NEXT: br i1 [[TMP3]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP10:![0-9]+]]
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; O23: middle.block:
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; O23-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[N_VEC]], [[NUMELEM]]
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; O23-NEXT: br i1 [[CMP_N]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY_PREHEADER]]
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; O23: for.body.preheader:
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; O23-NEXT: [[K_02_PH:%.*]] = phi i64 [ 0, [[FOR_BODY_LR_PH]] ], [ [[N_VEC]], [[MIDDLE_BLOCK]] ]
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; O23-NEXT: br label [[FOR_BODY:%.*]]
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; O23: for.body:
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; O23-NEXT: [[K_02:%.*]] = phi i64 [ [[INC:%.*]], [[FOR_BODY]] ], [ [[K_02_PH]], [[FOR_BODY_PREHEADER]] ]
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; O23-NEXT: [[ADD_PTR_I:%.*]] = getelementptr inbounds double, ptr [[TMP0]], i64 [[K_02]]
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; O23-NEXT: store double 2.000000e+00, ptr [[ADD_PTR_I]], align 8, !tbaa [[TBAA8]]
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; O23-NEXT: [[INC]] = add nuw i64 [[K_02]], 1
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; O23-NEXT: [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INC]], [[NUMELEM]]
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; O23-NEXT: br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP]], label [[FOR_BODY]], !llvm.loop [[LOOP13:![0-9]+]]
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; O23: for.cond.cleanup:
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; O23-NEXT: ret void
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;
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entry:
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br label %for.cond
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for.cond: ; preds = %for.body, %entry
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%k.0 = phi i64 [ 0, %entry ], [ %inc, %for.body ]
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%cmp = icmp ult i64 %k.0, %numElem
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br i1 %cmp, label %for.body, label %for.cond.cleanup
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for.body: ; preds = %for.cond
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%0 = load ptr, ptr %_M_start.i, align 8, !tbaa !3
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%add.ptr.i = getelementptr inbounds double, ptr %0, i64 %k.0
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store double 2.000000e+00, ptr %add.ptr.i, align 8, !tbaa !8
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%inc = add nuw i64 %k.0, 1
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br label %for.cond
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for.cond.cleanup: ; preds = %for.cond
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ret void
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}
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!llvm.module.flags = !{!0, !1}
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!llvm.ident = !{!2}
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!0 = !{i32 1, !"wchar_size", i32 4}
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!1 = !{i32 7, !"uwtable", i32 1}
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!2 = !{!"clang version 15.0.0 (https://github.com/llvm/llvm-project.git fc510998f7c287df2bc1304673e0cd8452d50b31)"}
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!3 = !{!4, !5, i64 0}
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!4 = !{!"_ZTSNSt12_Vector_baseIdSaIdEE17_Vector_impl_dataE", !5, i64 0, !5, i64 8, !5, i64 16}
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!5 = !{!"any pointer", !6, i64 0}
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!6 = !{!"omnipotent char", !7, i64 0}
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!7 = !{!"Simple C++ TBAA"}
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!8 = !{!9, !9, i64 0}
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!9 = !{!"double", !6, i64 0}
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