1228becf7d
This patch deduces `noundef` attributes for return values. IIUC, a function returns `noundef` values iff all of its return values are guaranteed not to be `undef` or `poison`. Definition of `noundef` from LangRef: ``` noundef This attribute applies to parameters and return values. If the value representation contains any undefined or poison bits, the behavior is undefined. Note that this does not refer to padding introduced by the type’s storage representation. ``` Alive2: https://alive2.llvm.org/ce/z/g8Eis6 Compile-time impact: http://llvm-compile-time-tracker.com/compare.php?from=30dcc33c4ea3ab50397a7adbe85fe977d4a400bd&to=c5e8738d4bfbf1e97e3f455fded90b791f223d74&stat=instructions:u |stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang| |--|--|--|--|--|--|--| |+0.01%|+0.01%|-0.01%|+0.01%|+0.03%|-0.04%|+0.01%| The motivation of this patch is to reduce the number of `freeze` insts and enable more optimizations.
61 lines
2.5 KiB
LLVM
61 lines
2.5 KiB
LLVM
; Check that we promote constant object in the source module and import it
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; even when it is referenced in some other GV initializer and/or is used
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; by store instructions.
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; RUN: opt -thinlto-bc %s -o %t1.bc
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; RUN: opt -thinlto-bc %p/Inputs/import-constant.ll -o %t2.bc
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; RUN: llvm-lto2 run -save-temps %t1.bc %t2.bc -o %t-out \
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; RUN: -import-constants-with-refs \
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; RUN: -r=%t1.bc,main,plx \
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; RUN: -r=%t1.bc,_Z6getObjv,l \
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; RUN: -r=%t2.bc,_Z6getObjv,pl \
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; RUN: -r=%t2.bc,val,pl \
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; RUN: -r=%t2.bc,outer,pl
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; RUN: llvm-dis %t-out.2.1.promote.bc -o - | FileCheck %s --check-prefix=PROMOTE
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; RUN: llvm-dis %t-out.1.3.import.bc -o - | FileCheck %s --check-prefix=IMPORT
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; RUN: llvm-dis %t-out.1.4.opt.bc -o - | FileCheck %s --check-prefix=OPT
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; Check when importing references is prohibited
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; RUN: llvm-lto2 run -save-temps %t1.bc %t2.bc -o %t-out-norefs \
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; RUN: -import-constants-with-refs=false \
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; RUN: -r=%t1.bc,main,plx \
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; RUN: -r=%t1.bc,_Z6getObjv,l \
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; RUN: -r=%t2.bc,_Z6getObjv,pl \
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; RUN: -r=%t2.bc,val,pl \
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; RUN: -r=%t2.bc,outer,pl
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; RUN: llvm-dis %t-out-norefs.1.3.import.bc -o - | FileCheck %s --check-prefix=NOREFS
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; Check that variable has been promoted in the source module
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; PROMOTE: @_ZL3Obj.llvm.{{.*}} = hidden constant %struct.S { i32 4, i32 8, ptr @val }
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; @outer is a write-only variable, so it's been converted to zeroinitializer.
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; IMPORT: @val = available_externally global i32 42
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; IMPORT-NEXT: @_ZL3Obj.llvm.{{.*}} = available_externally hidden constant %struct.S { i32 4, i32 8, ptr @val }
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; IMPORT-NEXT: @outer = internal local_unnamed_addr global %struct.Q zeroinitializer
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; @outer is a write-only variable that's stored to once, so the store and the global can be removed.
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; OPT-NOT: @outer
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; OPT: define dso_local noundef i32 @main()
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; OPT-NEXT: entry:
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; OPT-NEXT: ret i32 12
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; NOREFS: @_ZL3Obj.llvm.{{.*}} = external hidden constant %struct.S
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; NOREFS-NEXT: @outer = internal local_unnamed_addr global %struct.Q zeroinitializer
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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%struct.S = type { i32, i32, ptr }
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define dso_local i32 @main() local_unnamed_addr {
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entry:
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%call = tail call ptr @_Z6getObjv()
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%0 = load i32, ptr %call, align 8
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%v = getelementptr inbounds %struct.S, ptr %call, i64 0, i32 1
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%1 = load i32, ptr %v, align 4
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%add = add nsw i32 %1, %0
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ret i32 %add
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}
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declare dso_local ptr @_Z6getObjv() local_unnamed_addr
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