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.
91 lines
3.2 KiB
LLVM
91 lines
3.2 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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define void @matching_phi(i64 %a, ptr %b, i1 %cond) {
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; CHECK-LABEL: @matching_phi(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[COND:%.*]], label [[BB2:%.*]], label [[BB1:%.*]]
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; CHECK: bb1:
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; CHECK-NEXT: [[ADDB:%.*]] = getelementptr inbounds i8, ptr [[B:%.*]], i64 8
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; CHECK-NEXT: br label [[BB3:%.*]]
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; CHECK: bb2:
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; CHECK-NEXT: [[ADD_INT:%.*]] = add i64 [[A:%.*]], 1
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; CHECK-NEXT: [[ADD:%.*]] = inttoptr i64 [[ADD_INT]] to ptr
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; CHECK-NEXT: store float 1.000000e+01, ptr [[ADD]], align 4
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; CHECK-NEXT: br label [[BB3]]
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; CHECK: bb3:
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; CHECK-NEXT: [[A_ADDR_03:%.*]] = phi ptr [ [[ADDB]], [[BB1]] ], [ [[ADD]], [[BB2]] ]
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; CHECK-NEXT: [[I1:%.*]] = load float, ptr [[A_ADDR_03]], align 4
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; CHECK-NEXT: [[MUL_I:%.*]] = fmul float [[I1]], 4.200000e+01
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; CHECK-NEXT: store float [[MUL_I]], ptr [[A_ADDR_03]], align 4
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; CHECK-NEXT: ret void
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;
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entry:
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%cmp1 = icmp eq i1 %cond, 0
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%add.int = add i64 %a, 1
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%add = inttoptr i64 %add.int to ptr
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%addb = getelementptr inbounds float, ptr %b, i64 2
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%addb.int = ptrtoint ptr %addb to i64
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br i1 %cmp1, label %bb1, label %bb2
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bb1:
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br label %bb3
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bb2:
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store float 1.0e+01, ptr %add, align 4
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br label %bb3
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bb3:
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%a.addr.03 = phi ptr [ %addb, %bb1 ], [ %add, %bb2 ]
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%b.addr.02 = phi i64 [ %addb.int, %bb1 ], [ %add.int, %bb2 ]
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%i0 = inttoptr i64 %b.addr.02 to ptr
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%i1 = load float, ptr %i0, align 4
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%mul.i = fmul float %i1, 4.200000e+01
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store float %mul.i, ptr %a.addr.03, align 4
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ret void
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}
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define void @no_matching_phi(i64 %a, ptr %b, i1 %cond) {
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; CHECK-LABEL: @no_matching_phi(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[ADD_INT:%.*]] = add i64 [[A:%.*]], 1
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; CHECK-NEXT: [[ADDB:%.*]] = getelementptr inbounds i8, ptr [[B:%.*]], i64 8
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; CHECK-NEXT: br i1 [[COND:%.*]], label [[B:%.*]], label [[A:%.*]]
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; CHECK: A:
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; CHECK-NEXT: [[TMP0:%.*]] = inttoptr i64 [[ADD_INT]] to ptr
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; CHECK-NEXT: br label [[C:%.*]]
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; CHECK: B:
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; CHECK-NEXT: [[ADD:%.*]] = inttoptr i64 [[ADD_INT]] to ptr
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; CHECK-NEXT: store float 1.000000e+01, ptr [[ADD]], align 4
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; CHECK-NEXT: br label [[C]]
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; CHECK: C:
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; CHECK-NEXT: [[A_ADDR_03:%.*]] = phi ptr [ [[ADDB]], [[A]] ], [ [[ADD]], [[B]] ]
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; CHECK-NEXT: [[B_ADDR_02:%.*]] = phi ptr [ [[TMP0]], [[A]] ], [ [[ADDB]], [[B]] ]
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; CHECK-NEXT: [[I1:%.*]] = load float, ptr [[B_ADDR_02]], align 4
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; CHECK-NEXT: [[MUL_I:%.*]] = fmul float [[I1]], 4.200000e+01
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; CHECK-NEXT: store float [[MUL_I]], ptr [[A_ADDR_03]], align 4
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; CHECK-NEXT: ret void
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;
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entry:
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%cmp1 = icmp eq i1 %cond, 0
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%add.int = add i64 %a, 1
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%add = inttoptr i64 %add.int to ptr
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%addb = getelementptr inbounds float, ptr %b, i64 2
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%addb.int = ptrtoint ptr %addb to i64
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br i1 %cmp1, label %A, label %B
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A:
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br label %C
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B:
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store float 1.0e+01, ptr %add, align 4
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br label %C
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C:
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%a.addr.03 = phi ptr [ %addb, %A ], [ %add, %B ]
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%b.addr.02 = phi i64 [ %addb.int, %B ], [ %add.int, %A ]
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%i0 = inttoptr i64 %b.addr.02 to ptr
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%i1 = load float, ptr %i0, align 4
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%mul.i = fmul float %i1, 4.200000e+01
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store float %mul.i, ptr %a.addr.03, align 4
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ret void
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}
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