df1ef08c0c
When rewriting statepoints to make relocations explicit, we need to have a conservative but consistent notion of where a particular pointer is live at a particular site. The old code just used dominance, which is correct, but decidedly more conservative then it needed to be. This patch implements a simple dataflow algorithm that's run one per function (well, twice counting fixup after base pointer insertion). There's still lots of room to make this faster, but it's fast enough for all practical purposes today. Differential Revision: http://reviews.llvm.org/D8674 llvm-svn: 234657
101 lines
4.6 KiB
LLVM
101 lines
4.6 KiB
LLVM
; RUN: opt %s -rewrite-statepoints-for-gc -S 2>&1 | FileCheck %s
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declare i64 addrspace(1)* @generate_obj()
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declare void @use_obj(i64 addrspace(1)*)
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; The rewriting needs to make %obj loop variant by inserting a phi
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; of the original value and it's relocation.
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define void @def_use_safepoint() gc "statepoint-example" {
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; CHECK-LABEL: def_use_safepoint
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entry:
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%obj = call i64 addrspace(1)* @generate_obj()
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br label %loop
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loop:
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; CHECK: phi i64 addrspace(1)*
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; CHECK-DAG: [ %obj.relocated, %loop ]
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; CHECK-DAG: [ %obj, %entry ]
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call void @use_obj(i64 addrspace(1)* %obj)
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%safepoint_token = call i32 (void ()*, i32, i32, ...)* @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()* @do_safepoint, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
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br label %loop
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}
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declare void @do_safepoint()
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declare void @parse_point(i64 addrspace(1)*)
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define i64 addrspace(1)* @test1(i32 %caller, i8 addrspace(1)* %a, i8 addrspace(1)* %b, i32 %unknown) gc "statepoint-example" {
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; CHECK-LABEL: test1
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entry:
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br i1 undef, label %left, label %right
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left:
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%a.cast = bitcast i8 addrspace(1)* %a to i64 addrspace(1)*
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; CHECK: left:
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; CHECK-NEXT: %a.cast = bitcast i8 addrspace(1)* %a to i64 addrspace(1)*
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; CHECK-NEXT: [[CAST_L:%.*]] = bitcast i8 addrspace(1)* %a to i64 addrspace(1)*
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; Our safepoint placement pass calls removeUnreachableBlocks, which does a bunch
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; of simplifications to branch instructions. This bug is visible only when
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; there are multiple branches into the same block from the same predecessor, and
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; the following ceremony is to make that artefact survive a call to
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; removeUnreachableBlocks. As an example, "br i1 undef, label %merge, label %merge"
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; will get simplified to "br label %merge" by removeUnreachableBlocks.
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switch i32 %unknown, label %right [ i32 0, label %merge
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i32 1, label %merge
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i32 5, label %merge
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i32 3, label %right ]
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right:
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%b.cast = bitcast i8 addrspace(1)* %b to i64 addrspace(1)*
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br label %merge
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; CHECK: right:
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; CHECK-NEXT: %b.cast = bitcast i8 addrspace(1)* %b to i64 addrspace(1)*
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; CHECK-NEXT: [[CAST_R:%.*]] = bitcast i8 addrspace(1)* %b to i64 addrspace(1)*
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merge:
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; CHECK: merge:
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; CHECK-NEXT: %base_phi = phi i64 addrspace(1)* [ [[CAST_L]], %left ], [ [[CAST_L]], %left ], [ [[CAST_L]], %left ], [ [[CAST_R]], %right ], !is_base_value !0
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%value = phi i64 addrspace(1)* [ %a.cast, %left], [ %a.cast, %left], [ %a.cast, %left], [ %b.cast, %right]
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%safepoint_token = call i32 (void (i64 addrspace(1)*)*, i32, i32, ...)* @llvm.experimental.gc.statepoint.p0f_isVoidp1i64f(void (i64 addrspace(1)*)* @parse_point, i32 1, i32 0, i64 addrspace(1)* %value, i32 5, i32 0, i32 0, i32 0, i32 0, i32 0)
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ret i64 addrspace(1)* %value
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}
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;; The purpose of this test is to ensure that when two live values share a
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;; base defining value with inherent conflicts, we end up with a *single*
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;; base phi/select per such node. This is testing an optimization, not a
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;; fundemental correctness criteria
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define void @test2(i1 %cnd, i64 addrspace(1)* %base_obj, i64 addrspace(1)* %base_arg2) gc "statepoint-example" {
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; CHECK-LABEL: @test2
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entry:
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%obj = getelementptr i64, i64 addrspace(1)* %base_obj, i32 1
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br label %loop
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loop: ; preds = %loop, %entry
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; CHECK-LABEL: loop
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; CHECK: %base_phi = phi i64 addrspace(1)*
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; CHECK-DAG: [ %base_obj, %entry ]
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; Given the two selects are equivelent, so are their base phis - ideally,
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; we'd have commoned these, but that's a missed optimization, not correctness.
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; CHECK-DAG: [ [[DISCARD:%base_select.*.relocated]], %loop ]
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; CHECK-NOT: base_phi2
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; CHECK: next = select
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; CHECK: base_select
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; CHECK: extra2 = select
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; CHECK: base_select
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; CHECK: statepoint
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;; Both 'next' and 'extra2' are live across the backedge safepoint...
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%current = phi i64 addrspace(1)* [ %obj, %entry ], [ %next, %loop ]
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%extra = phi i64 addrspace(1)* [ %obj, %entry ], [ %extra2, %loop ]
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%nexta = getelementptr i64, i64 addrspace(1)* %current, i32 1
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%next = select i1 %cnd, i64 addrspace(1)* %nexta, i64 addrspace(1)* %base_arg2
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%extra2 = select i1 %cnd, i64 addrspace(1)* %nexta, i64 addrspace(1)* %base_arg2
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%safepoint_token = call i32 (void ()*, i32, i32, ...)* @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()* @foo, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
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br label %loop
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}
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declare void @foo()
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declare i32 @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()*, i32, i32, ...)
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declare i32 @llvm.experimental.gc.statepoint.p0f_isVoidp1i64f(void (i64 addrspace(1)*)*, i32, i32, ...)
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