f562fc8dbf
Teach LICM to hoist stores out of loops when the store writes to a location otherwise unused in the loop, writes a value which is invariant, and is guaranteed to execute if the loop is entered. Worth noting is that this transformation is partially overlapping with the existing promotion transformation. Reasons this is worthwhile anyway include: * For multi-exit loops, this doesn't require duplication of the store. * It kicks in for case where we can't prove we exit through a normal exit (i.e. we may throw), but can prove the store executes before that possible side exit. Differential Revision: https://reviews.llvm.org/D50925 llvm-svn: 340974
224 lines
6.0 KiB
LLVM
224 lines
6.0 KiB
LLVM
; RUN: opt < %s -S -basicaa -licm | FileCheck %s
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; RUN: opt -aa-pipeline=basic-aa -passes='require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s
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; Check that we can hoist unordered loads
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define i32 @test1(i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%i = phi i32 [ %inc, %loop ], [ 0, %entry ]
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%val = load atomic i32, i32* %y unordered, align 4
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%inc = add nsw i32 %i, 1
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%exitcond = icmp eq i32 %inc, %val
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %val
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; CHECK-LABEL: define i32 @test1(
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; CHECK: load atomic
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; CHECK-NEXT: br label %loop
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}
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; Check that we don't sink/hoist monotonic loads
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; (Strictly speaking, it's not forbidden, but it's supposed to be possible to
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; use monotonic for spinlock-like constructs.)
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define i32 @test2(i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%val = load atomic i32, i32* %y monotonic, align 4
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%exitcond = icmp ne i32 %val, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %val
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; CHECK-LABEL: define i32 @test2(
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; CHECK: load atomic
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; CHECK-NEXT: %exitcond = icmp ne
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; CHECK-NEXT: br i1 %exitcond, label %end, label %loop
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}
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; Check that we hoist unordered around monotonic.
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; (The noalias shouldn't be necessary in theory, but LICM isn't quite that
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; smart yet.)
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define i32 @test3(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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%valb = load atomic i32, i32* %x unordered, align 4
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%exitcond = icmp ne i32 %vala, %valb
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test3(
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; CHECK: load atomic i32, i32* %x unordered
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; CHECK-NEXT: br label %loop
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}
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; We can sink an unordered store
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define i32 @test4(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %x unordered, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test4(
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; CHECK-LABEL: loop:
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NOT: store
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; CHECK-LABEL: end:
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; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %vala
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; CHECK: store atomic i32 %[[LCSSAPHI]], i32* %x unordered, align 4
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}
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; We currently don't handle ordered atomics.
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define i32 @test5(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %x release, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test5(
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NEXT: store atomic
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}
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; We currently don't touch volatiles
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define i32 @test6(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store volatile i32 %vala, i32* %x, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test6(
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NEXT: store volatile
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}
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; We currently don't touch volatiles
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define i32 @test6b(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic volatile i32 %vala, i32* %x unordered, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test6b(
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NEXT: store atomic volatile
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}
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; Mixing unorder atomics and normal loads/stores is
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; current unimplemented
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define i32 @test7(i32* nocapture noalias %x, i32* nocapture %y) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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store i32 5, i32* %x
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %x unordered, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test7(
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; CHECK: store i32 5, i32* %x
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; CHECK-NEXT: load atomic i32, i32* %y
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; CHECK-NEXT: store atomic i32
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}
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; Three provably noalias locations - we can sink normal and unordered, but
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; not monotonic
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define i32 @test7b(i32* nocapture noalias %x, i32* nocapture %y, i32* noalias nocapture %z) nounwind uwtable ssp {
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entry:
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br label %loop
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loop:
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store i32 5, i32* %x
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %z unordered, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test7b(
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; CHECK-LABEL: entry:
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; CHECK: store i32 5, i32* %x
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; CHECK-LABEL: loop:
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-LABEL: end:
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; CHECK: store atomic i32 %{{.+}}, i32* %z unordered, align 4
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}
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define i32 @test8(i32* nocapture noalias %x, i32* nocapture %y) {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %x unordered, align 4
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fence release
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test8(
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; CHECK-LABEL: loop:
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NEXT: store atomic
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; CHECK-NEXT: fence
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}
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; Exact semantics of monotonic accesses are a bit vague in the C++ spec,
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; for the moment, be conservative and don't touch them.
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define i32 @test9(i32* nocapture noalias %x, i32* nocapture %y) {
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entry:
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br label %loop
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loop:
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%vala = load atomic i32, i32* %y monotonic, align 4
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store atomic i32 %vala, i32* %x monotonic, align 4
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%exitcond = icmp ne i32 %vala, 0
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br i1 %exitcond, label %end, label %loop
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end:
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ret i32 %vala
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; CHECK-LABEL: define i32 @test9(
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; CHECK-LABEL: loop:
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; CHECK: load atomic i32, i32* %y monotonic
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; CHECK-NEXT: store atomic i32 %vala, i32* %x monotonic, align 4
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}
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