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54e8749794
This pass implements whole program optimization of virtual calls in cases where we know (via bitset information) that the list of callees is fixed. This includes the following: - Single implementation devirtualization: if a virtual call has a single possible callee, replace all calls with a direct call to that callee. - Virtual constant propagation: if the virtual function's return type is an integer <=64 bits and all possible callees are readnone, for each class and each list of constant arguments: evaluate the function, store the return value alongside the virtual table, and rewrite each virtual call as a load from the virtual table. - Uniform return value optimization: if the conditions for virtual constant propagation hold and each function returns the same constant value, replace each virtual call with that constant. - Unique return value optimization for i1 return values: if the conditions for virtual constant propagation hold and a single vtable's function returns 0, or a single vtable's function returns 1, replace each virtual call with a comparison of the vptr against that vtable's address. Differential Revision: http://reviews.llvm.org/D16795 llvm-svn: 260312
38 lines
1.1 KiB
LLVM
38 lines
1.1 KiB
LLVM
; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
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target datalayout = "e-p:64:64"
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target triple = "x86_64-unknown-linux-gnu"
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@vt1 = global [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf1 to i8*)]
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@vt2 = global [1 x i8*] [i8* bitcast (i32 (i8*, i32)* @vf2 to i8*)]
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define i32 @vf1(i8* %this, i32 %arg) readnone {
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ret i32 %arg
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}
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define i32 @vf2(i8* %this, i32 %arg) readnone {
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ret i32 %arg
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}
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; CHECK: define void @call
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define void @call(i8* %obj, i32 %arg) {
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%vtableptr = bitcast i8* %obj to [1 x i8*]**
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%vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
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%vtablei8 = bitcast [1 x i8*]* %vtable to i8*
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%p = call i1 @llvm.bitset.test(i8* %vtablei8, metadata !"bitset")
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call void @llvm.assume(i1 %p)
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%fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
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%fptr = load i8*, i8** %fptrptr
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%fptr_casted = bitcast i8* %fptr to i32 (i8*, i32)*
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; CHECK: call i32 %
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%result = call i32 %fptr_casted(i8* %obj, i32 %arg)
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ret void
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}
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declare i1 @llvm.bitset.test(i8*, metadata)
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declare void @llvm.assume(i1)
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!0 = !{!"bitset", [1 x i8*]* @vt1, i32 0}
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!1 = !{!"bitset", [1 x i8*]* @vt2, i32 0}
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!llvm.bitsets = !{!0}
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