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clang-p2996/llvm/test/Transforms/InstCombine/select-cmp-br.ll
Nikita Popov 90ba33099c [InstCombine] Canonicalize constant GEPs to i8 source element type (#68882) 
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.
2024-01-24 15:25:29 +01:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; Replace a 'select' with 'or' in 'select - cmp [eq|ne] - br' sequence
; RUN: opt -passes=instcombine -S < %s | FileCheck %s
%struct.S = type { ptr, i32, i32 }
%C = type <{ %struct.S }>
declare void @bar(ptr)
declare void @foobar()
define void @test1(ptr %arg) {
; CHECK-LABEL: @test1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[M:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[ARG]], i64 16
; CHECK-NEXT: [[N:%.*]] = load ptr, ptr [[TMP1]], align 8
; CHECK-NEXT: [[TMP5_NOT:%.*]] = icmp eq ptr [[M]], [[N]]
; CHECK-NEXT: br i1 [[TMP5_NOT]], label [[BB8:%.*]], label [[BB10:%.*]]
; CHECK: bb:
; CHECK-NEXT: ret void
; CHECK: bb8:
; CHECK-NEXT: tail call void @bar(ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb10:
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[M]], i64 72
; CHECK-NEXT: [[TMP4:%.*]] = load ptr, ptr [[TMP2]], align 8
; CHECK-NEXT: [[TMP11:%.*]] = tail call i64 [[TMP4]](ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB]]
;
entry:
%m = load ptr, ptr %arg, align 8
%tmp1 = getelementptr inbounds %C, ptr %arg, i64 1, i32 0, i32 0
%n = load ptr, ptr %tmp1, align 8
%tmp2 = getelementptr inbounds i64, ptr %m, i64 9
%tmp4 = load ptr, ptr %tmp2, align 8
%tmp5 = icmp eq ptr %m, %n
%tmp6 = select i1 %tmp5, ptr %arg, ptr null
%tmp7 = icmp eq ptr %tmp6, null
br i1 %tmp7, label %bb10, label %bb8
bb: ; preds = %bb10, %bb8
ret void
bb8: ; preds = %entry
tail call void @bar(ptr %tmp6)
br label %bb
bb10: ; preds = %entry
%tmp11 = tail call i64 %tmp4(ptr %arg)
br label %bb
}
define void @test2(ptr %arg) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[M:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[ARG]], i64 16
; CHECK-NEXT: [[N:%.*]] = load ptr, ptr [[TMP1]], align 8
; CHECK-NEXT: [[TMP5:%.*]] = icmp eq ptr [[M]], [[N]]
; CHECK-NEXT: br i1 [[TMP5]], label [[BB10:%.*]], label [[BB8:%.*]]
; CHECK: bb:
; CHECK-NEXT: ret void
; CHECK: bb8:
; CHECK-NEXT: tail call void @bar(ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb10:
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[M]], i64 72
; CHECK-NEXT: [[TMP4:%.*]] = load ptr, ptr [[TMP2]], align 8
; CHECK-NEXT: [[TMP11:%.*]] = tail call i64 [[TMP4]](ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB]]
;
entry:
%m = load ptr, ptr %arg, align 8
%tmp1 = getelementptr inbounds %C, ptr %arg, i64 1, i32 0, i32 0
%n = load ptr, ptr %tmp1, align 8
%tmp2 = getelementptr inbounds i64, ptr %m, i64 9
%tmp4 = load ptr, ptr %tmp2, align 8
%tmp5 = icmp eq ptr %m, %n
%tmp6 = select i1 %tmp5, ptr null, ptr %arg
%tmp7 = icmp eq ptr %tmp6, null
br i1 %tmp7, label %bb10, label %bb8
bb: ; preds = %bb10, %bb8
ret void
bb8: ; preds = %entry
tail call void @bar(ptr %tmp6)
br label %bb
bb10: ; preds = %entry
%tmp11 = tail call i64 %tmp4(ptr %arg)
br label %bb
}
define void @test3(ptr %arg) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[M:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[ARG]], i64 16
; CHECK-NEXT: [[N:%.*]] = load ptr, ptr [[TMP1]], align 8
; CHECK-NEXT: [[TMP5:%.*]] = icmp eq ptr [[M]], [[N]]
; CHECK-NEXT: br i1 [[TMP5]], label [[BB8:%.*]], label [[BB10:%.*]]
; CHECK: bb:
; CHECK-NEXT: ret void
; CHECK: bb8:
; CHECK-NEXT: tail call void @bar(ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb10:
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[M]], i64 72
; CHECK-NEXT: [[TMP4:%.*]] = load ptr, ptr [[TMP2]], align 8
; CHECK-NEXT: [[TMP11:%.*]] = tail call i64 [[TMP4]](ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB]]
;
entry:
%m = load ptr, ptr %arg, align 8
%tmp1 = getelementptr inbounds %C, ptr %arg, i64 1, i32 0, i32 0
%n = load ptr, ptr %tmp1, align 8
%tmp2 = getelementptr inbounds i64, ptr %m, i64 9
%tmp4 = load ptr, ptr %tmp2, align 8
%tmp5 = icmp eq ptr %m, %n
%tmp6 = select i1 %tmp5, ptr %arg, ptr null
%tmp7 = icmp ne ptr %tmp6, null
br i1 %tmp7, label %bb8, label %bb10
bb: ; preds = %bb10, %bb8
ret void
bb8: ; preds = %entry
tail call void @bar(ptr %tmp6)
br label %bb
bb10: ; preds = %entry
%tmp11 = tail call i64 %tmp4(ptr %arg)
br label %bb
}
define void @test4(ptr %arg) {
; CHECK-LABEL: @test4(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[M:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[ARG]], i64 16
; CHECK-NEXT: [[N:%.*]] = load ptr, ptr [[TMP1]], align 8
; CHECK-NEXT: [[TMP5:%.*]] = icmp eq ptr [[M]], [[N]]
; CHECK-NEXT: br i1 [[TMP5]], label [[BB10:%.*]], label [[BB8:%.*]]
; CHECK: bb:
; CHECK-NEXT: ret void
; CHECK: bb8:
; CHECK-NEXT: tail call void @bar(ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb10:
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[M]], i64 72
; CHECK-NEXT: [[TMP4:%.*]] = load ptr, ptr [[TMP2]], align 8
; CHECK-NEXT: [[TMP11:%.*]] = tail call i64 [[TMP4]](ptr nonnull [[ARG]])
; CHECK-NEXT: br label [[BB]]
;
entry:
%m = load ptr, ptr %arg, align 8
%tmp1 = getelementptr inbounds %C, ptr %arg, i64 1, i32 0, i32 0
%n = load ptr, ptr %tmp1, align 8
%tmp2 = getelementptr inbounds i64, ptr %m, i64 9
%tmp4 = load ptr, ptr %tmp2, align 8
%tmp5 = icmp eq ptr %m, %n
%tmp6 = select i1 %tmp5, ptr null, ptr %arg
%tmp7 = icmp ne ptr %tmp6, null
br i1 %tmp7, label %bb8, label %bb10
bb: ; preds = %bb10, %bb8
ret void
bb8: ; preds = %entry
tail call void @bar(ptr %tmp6)
br label %bb
bb10: ; preds = %entry
%tmp11 = tail call i64 %tmp4(ptr %arg)
br label %bb
}
define void @test5(ptr %arg, i1 %arg1) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP2_NOT1:%.*]] = icmp eq ptr [[ARG:%.*]], null
; CHECK-NEXT: [[TMP2_NOT:%.*]] = select i1 [[ARG1:%.*]], i1 true, i1 [[TMP2_NOT1]]
; CHECK-NEXT: br i1 [[TMP2_NOT]], label [[BB5:%.*]], label [[BB3:%.*]]
; CHECK: bb:
; CHECK-NEXT: ret void
; CHECK: bb3:
; CHECK-NEXT: tail call void @bar(ptr [[ARG]])
; CHECK-NEXT: br label [[BB:%.*]]
; CHECK: bb5:
; CHECK-NEXT: tail call void @foobar()
; CHECK-NEXT: br label [[BB]]
;
entry:
%tmp = select i1 %arg1, ptr null, ptr %arg
%tmp2 = icmp ne ptr %tmp, null
br i1 %tmp2, label %bb3, label %bb5
bb: ; preds = %bb5, %bb3
ret void
bb3: ; preds = %entry
tail call void @bar(ptr %tmp)
br label %bb
bb5: ; preds = %entry
tail call void @foobar()
br label %bb
}
; Negative test. Must not trigger the select-cmp-br combine because the result
; of the select is used in both flows following the br (the special case where
; the conditional branch has the same target for both flows).
define i32 @test6(i32 %arg, i1 %arg1) {
; CHECK-LABEL: @test6(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 false, label [[BB:%.*]], label [[BB]]
; CHECK: bb:
; CHECK-NEXT: [[TMP:%.*]] = select i1 [[ARG1:%.*]], i32 [[ARG:%.*]], i32 0
; CHECK-NEXT: ret i32 [[TMP]]
;
entry:
%tmp = select i1 %arg1, i32 %arg, i32 0
%tmp2 = icmp eq i32 %tmp, 0
br i1 %tmp2, label %bb, label %bb
bb: ; preds = %entry, %entry
ret i32 %tmp
}
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