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.
43 lines
1.8 KiB
LLVM
43 lines
1.8 KiB
LLVM
; RUN: opt -module-summary %s -o %t1.bc
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; RUN: opt -module-summary %p/Inputs/index-const-prop-alias.ll -o %t2.bc
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; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,pl -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
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; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,pl -save-temps -o %t3
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; RUN: llvm-dis %t3.1.3.import.bc -o - | FileCheck %s --check-prefix=IMPORT
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; RUN: llvm-dis %t3.1.5.precodegen.bc -o - | FileCheck %s --check-prefix=CODEGEN
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; When ret_ptr is preserved we return pointer to alias, so we can't internalize aliasee
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; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,plx -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
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; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,pl -save-temps -o %t4
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; RUN: llvm-dis %t4.1.3.import.bc -o - | FileCheck %s --check-prefix=PRESERVED
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; When g.alias is preserved we can't internalize aliasee either
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; RUN: llvm-lto2 run %t1.bc -r=%t1.bc,main,plx -r=%t1.bc,ret_ptr,pl -r=%t1.bc,g.alias,l -r=%t1.bc,g,l \
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; RUN: %t2.bc -r=%t2.bc,g,pl -r=%t2.bc,g.alias,plx -save-temps -o %t5
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; RUN: llvm-dis %t5.1.3.import.bc -o - | FileCheck %s --check-prefix=PRESERVED
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; We currently don't support importing aliases
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; IMPORT: @g.alias = external global i32
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; IMPORT-NEXT: @g = internal global i32 42, align 4 #0
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; IMPORT: attributes #0 = { "thinlto-internalize" }
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; CODEGEN: define dso_local noundef i32 @main
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; CODEGEN-NEXT: ret i32 42
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; PRESERVED: @g.alias = external global i32
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; PRESERVED-NEXT: @g = available_externally global i32 42, align 4
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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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@g.alias = external global i32
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@g = external global i32
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define i32 @main() {
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%v = load i32, ptr @g
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ret i32 %v
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}
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define ptr @ret_ptr() {
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ret ptr @g.alias
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}
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