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The statepoint intrinsics are intended to enable precise root tracking through the compiler as to support garbage collectors of all types. The addition of the statepoint intrinsics to LLVM should have no impact on the compilation of any program which does not contain them. There are no side tables created, no extra metadata, and no inhibited optimizations. A statepoint works by transforming a call site (or safepoint poll site) into an explicit relocation operation. It is the frontend's responsibility (or eventually the safepoint insertion pass we've developed, but that's not part of this patch series) to ensure that any live pointer to a GC object is correctly added to the statepoint and explicitly relocated. The relocated value is just a normal SSA value (as seen by the optimizer), so merges of relocated and unrelocated values are just normal phis. The explicit relocation operation, the fact the statepoint is assumed to clobber all memory, and the optimizers standard semantics ensure that the relocations flow through IR optimizations correctly. This is the first patch in a small series. This patch contains only the IR parts; the documentation and backend support will be following separately. The entire series can be seen as one combined whole in http://reviews.llvm.org/D5683. Reviewed by: atrick, ributzka llvm-svn: 223078
51 lines
2.2 KiB
LLVM
51 lines
2.2 KiB
LLVM
; RUN: opt -S %s -verify | FileCheck %s
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declare void @use(...)
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declare i8 addrspace(1)* @llvm.gc.relocate.p1i8(i32, i32, i32)
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declare i32 @llvm.statepoint.p0f_isVoidf(void ()*, i32, i32, ...)
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;; Basic usage
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define i8 addrspace(1)* @test1(i8 addrspace(1)* %arg) {
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entry:
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%cast = bitcast i8 addrspace(1)* %arg to i64 addrspace(1)*
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%safepoint_token = call i32 (void ()*, i32, i32, ...)* @llvm.statepoint.p0f_isVoidf(void ()* undef, i32 0, i32 0, i32 5, i32 0, i32 0, i32 0, i32 10, i32 0, i8 addrspace(1)* %arg, i64 addrspace(1)* %cast, i8 addrspace(1)* %arg, i8 addrspace(1)* %arg)
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%reloc = call i8 addrspace(1)* @llvm.gc.relocate.p1i8(i32 %safepoint_token, i32 9, i32 10)
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;; It is perfectly legal to relocate the same value multiple times...
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%reloc2 = call i8 addrspace(1)* @llvm.gc.relocate.p1i8(i32 %safepoint_token, i32 9, i32 10)
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%reloc3 = call i8 addrspace(1)* @llvm.gc.relocate.p1i8(i32 %safepoint_token, i32 10, i32 9)
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ret i8 addrspace(1)* %reloc
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; CHECK-LABEL: test1
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; CHECK: statepoint
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; CHECK: gc.relocate
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; CHECK: gc.relocate
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; CHECK: gc.relocate
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; CHECK: ret i8 addrspace(1)* %reloc
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}
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; This test catches two cases where the verifier was too strict:
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; 1) A base doesn't need to be relocated if it's never used again
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; 2) A value can be replaced by one which is known equal. This
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; means a potentially derived pointer can be known base and that
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; we can't check that derived pointer are never bases.
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define void @test2(i8 addrspace(1)* %arg, i64 addrspace(1)* %arg2) {
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entry:
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%cast = bitcast i8 addrspace(1)* %arg to i64 addrspace(1)*
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%c = icmp eq i64 addrspace(1)* %cast, %arg2
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br i1 %c, label %equal, label %notequal
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notequal:
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ret void
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equal:
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%safepoint_token = call i32 (void ()*, i32, i32, ...)* @llvm.statepoint.p0f_isVoidf(void ()* undef, i32 0, i32 0, i32 5, i32 0, i32 0, i32 0, i32 10, i32 0, i8 addrspace(1)* %arg, i64 addrspace(1)* %cast, i8 addrspace(1)* %arg, i8 addrspace(1)* %arg)
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%reloc = call i8 addrspace(1)* @llvm.gc.relocate.p1i8(i32 %safepoint_token, i32 9, i32 10)
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call void undef(i8 addrspace(1)* %reloc)
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ret void
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; CHECK-LABEL: test2
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; CHECK-LABEL: equal
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; CHECK: statepoint
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; CHECK-NEXT: %reloc = call
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; CHECK-NEXT: call
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; CHECK-NEXT: ret voi
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}
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