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a404b6f421
There can be various constant pointers in the IR which do not get relocated at a safepoint. One example is the address of a global variable. Another example is a pointer created via inttoptr. Note that the optimizer itself likes to create such inttoptrs when locally propagating constants through dynamically dead code. To deal with this, we need to exclude uses of constants from contributing to the liveness of a safepoint which might reach that use. At some later date, it might be worth exploring what could be done to support the relocation of various special types of "constants", but that's future work. Differential Revision: http://reviews.llvm.org/D9236 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235821 91177308-0d34-0410-b5e6-96231b3b80d8
62 lines
2.0 KiB
LLVM
62 lines
2.0 KiB
LLVM
; RUN: opt -S -rewrite-statepoints-for-gc %s | FileCheck %s
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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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; constants don't get relocated.
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define i8 @test() gc "statepoint-example" {
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; CHECK-LABEL: @test
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; CHECK: gc.statepoint
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; CHECK-NEXT: load i8, i8 addrspace(1)* inttoptr (i64 15 to i8 addrspace(1)*)
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entry:
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call i32 (void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()* @foo, i32 0, i32 0, i32 0)
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%res = load i8, i8 addrspace(1)* inttoptr (i64 15 to i8 addrspace(1)*)
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ret i8 %res
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}
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; Mostly just here to show reasonable code test can come from.
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define i8 @test2(i8 addrspace(1)* %p) gc "statepoint-example" {
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; CHECK-LABEL: @test2
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; CHECK: gc.statepoint
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; CHECK-NEXT: gc.relocate
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; CHECK-NEXT: icmp
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entry:
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call i32 (void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()* @foo, i32 0, i32 0, i32 0)
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%cmp = icmp eq i8 addrspace(1)* %p, null
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br i1 %cmp, label %taken, label %not_taken
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taken:
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ret i8 0
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not_taken:
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%cmp2 = icmp ne i8 addrspace(1)* %p, null
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br i1 %cmp2, label %taken, label %dead
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dead:
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; We see that dead can't be reached, but the optimizer might not. It's
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; completely legal for it to exploit the fact that if dead executed, %p
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; would have to equal null. This can produce intermediate states which
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; look like that of test above, even if arbitrary constant addresses aren't
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; legal in the source language
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%addr = getelementptr i8, i8 addrspace(1)* %p, i32 15
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%res = load i8, i8addrspace(1)* %addr
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ret i8 %res
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}
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@G = addrspace(1) global i8 5
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; Globals don't move and thus don't get relocated
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define i8 @test3(i1 %always_true) gc "statepoint-example" {
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; CHECK-LABEL: @test3
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; CHECK: gc.statepoint
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; CHECK-NEXT: load i8, i8 addrspace(1)* @G
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entry:
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call i32 (void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(void ()* @foo, i32 0, i32 0, i32 0)
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%res = load i8, i8 addrspace(1)* @G, align 1
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ret i8 %res
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}
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