llvm-project/llvm/test/CodeGen/BPF/is_trunc_free.ll

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[BPF] implement isTruncateFree and isZExtFree in BPFTargetLowering Currently, isTruncateFree() and isZExtFree() callbacks return false as they are not implemented in BPF backend. This may cause suboptimal code generation. For example, if the load in the context of zero extension has more than one use, the pattern zextload{i8,i16,i32} will not be generated. Rather, the load will be matched first and then the result is zero extended. For example, in the test together with this commit, we have I1: %0 = load i32, i32* %data_end1, align 4, !tbaa !2 I2: %conv = zext i32 %0 to i64 ... I3: %2 = load i32, i32* %data, align 4, !tbaa !7 I4: %conv2 = zext i32 %2 to i64 ... I5: %4 = trunc i64 %sub.ptr.lhs.cast to i32 I6: %conv13 = sub i32 %4, %2 ... The I1 and I2 will match to one zextloadi32 DAG node, where SUBREG_TO_REG is used to convert a 32bit register to 64bit one. During code generation, SUBREG_TO_REG is a noop. The %2 in I3 is used in both I4 and I6. If isTruncateFree() is false, the current implementation will generate a SLL_ri and SRL_ri for the zext part during lowering. This patch implement isTruncateFree() in the BPF backend, so for the above example, I3 and I4 will generate a zextloadi32 DAG node with SUBREG_TO_REG is generated during lowering to Machine IR. isZExtFree() is also implemented as it should help code gen as well. This patch also enables the change in https://reviews.llvm.org/D73985 since it won't kick in generates MOV_32_64 machine instruction. Differential Revision: https://reviews.llvm.org/D74101
2020-02-06 02:27:43 +08:00
; RUN: llc -march=bpfel -mattr=+alu32 < %s | FileCheck %s
; Source:
; struct env_t {
; unsigned data;
; unsigned data_end;
; };
; extern int work(struct env_t *skb, unsigned offset);
; int test(struct env_t *skb)
; {
; void *cursor, *data_end;
; struct env_t *srh, *ip;
;
; data_end = (void *)(long)skb->data_end;
; cursor = (void *)(long)skb->data;
;
; ip = cursor; cursor += sizeof(*ip);
; if ((void *)ip + sizeof(*ip) > data_end)
; return 0;
;
; srh = cursor; cursor += sizeof(*srh);
; if ((void *)srh + sizeof(*srh) > data_end)
; return 0;
;
; return work(skb, (char *)srh - (char *)(long)skb->data);
; }
; Compilation flag:
; clang -target bpf -O2 -emit-llvm -S test.c
%struct.env_t = type { i32, i32 }
; Function Attrs: nounwind
define dso_local i32 @test(%struct.env_t* %skb) local_unnamed_addr #0 {
entry:
%data_end1 = getelementptr inbounds %struct.env_t, %struct.env_t* %skb, i64 0, i32 1
%0 = load i32, i32* %data_end1, align 4, !tbaa !2
%conv = zext i32 %0 to i64
%1 = inttoptr i64 %conv to i8*
%data = getelementptr inbounds %struct.env_t, %struct.env_t* %skb, i64 0, i32 0
%2 = load i32, i32* %data, align 4, !tbaa !7
%conv2 = zext i32 %2 to i64
%3 = inttoptr i64 %conv2 to i8*
%add.ptr = getelementptr i8, i8* %3, i64 8
%cmp = icmp ugt i8* %add.ptr, %1
%add.ptr6 = getelementptr i8, i8* %3, i64 16
%cmp7 = icmp ugt i8* %add.ptr6, %1
%or.cond = or i1 %cmp, %cmp7
br i1 %or.cond, label %cleanup, label %if.end10
if.end10: ; preds = %entry
%sub.ptr.lhs.cast = ptrtoint i8* %add.ptr to i64
%4 = trunc i64 %sub.ptr.lhs.cast to i32
%conv13 = sub i32 %4, %2
%call = tail call i32 @work(%struct.env_t* nonnull %skb, i32 %conv13) #2
br label %cleanup
cleanup: ; preds = %entry, %if.end10
%retval.0 = phi i32 [ %call, %if.end10 ], [ 0, %entry ]
ret i32 %retval.0
}
; CHECK: w{{[0-9]+}} = *(u32 *)(r{{[0-9]+}} + 0)
; CHECK-NOT: w{{[0-9]+}} = w{{[0-9]+}}
declare dso_local i32 @work(%struct.env_t*, i32) local_unnamed_addr #1
attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind }
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 016d3ce1f4b07ee3056f7c10fedb24c441c4870f)"}
!2 = !{!3, !4, i64 4}
!3 = !{!"env_t", !4, i64 0, !4, i64 4}
!4 = !{!"int", !5, i64 0}
!5 = !{!"omnipotent char", !6, i64 0}
!6 = !{!"Simple C/C++ TBAA"}
!7 = !{!3, !4, i64 0}