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https://github.com/c64scene-ar/llvm-6502.git
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5a81e14385
This patch introduces a new mechanism that allows IR modules to co-operatively build pointer sets corresponding to addresses within a given set of globals. One particular use case for this is to allow a C++ program to efficiently verify (at each call site) that a vtable pointer is in the set of valid vtable pointers for the class or its derived classes. One way of doing this is for a toolchain component to build, for each class, a bit set that maps to the memory region allocated for the vtables, such that each 1 bit in the bit set maps to a valid vtable for that class, and lay out the vtables next to each other, to minimize the total size of the bit sets. The patch introduces a metadata format for representing pointer sets, an '@llvm.bitset.test' intrinsic and an LTO lowering pass that lays out the globals and builds the bitsets, and documents the new feature. Differential Revision: http://reviews.llvm.org/D7288 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230054 91177308-0d34-0410-b5e6-96231b3b80d8
35 lines
877 B
LLVM
35 lines
877 B
LLVM
; RUN: opt -S -lowerbitsets < %s | FileCheck %s
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target datalayout = "e-p:32:32"
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@a = constant i32 1
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@b = constant [2 x i32] [i32 2, i32 3]
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!0 = !{!"bitset1", i32* @a, i32 0}
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!1 = !{!"bitset1", [2 x i32]* @b, i32 4}
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!llvm.bitsets = !{ !0, !1 }
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declare i1 @llvm.bitset.test(i8* %ptr, metadata %bitset) nounwind readnone
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; CHECK: @foo(
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define i1 @foo() {
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; CHECK: ret i1 true
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%x = call i1 @llvm.bitset.test(i8* bitcast (i32* @a to i8*), metadata !"bitset1")
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ret i1 %x
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}
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; CHECK: @bar(
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define i1 @bar() {
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; CHECK: ret i1 true
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%x = call i1 @llvm.bitset.test(i8* bitcast (i32* getelementptr ([2 x i32]* @b, i32 0, i32 1) to i8*), metadata !"bitset1")
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ret i1 %x
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}
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; CHECK: @baz(
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define i1 @baz() {
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; CHECK-NOT: ret i1 true
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%x = call i1 @llvm.bitset.test(i8* bitcast (i32* getelementptr ([2 x i32]* @b, i32 0, i32 0) to i8*), metadata !"bitset1")
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ret i1 %x
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}
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