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This intrinsic takes two arguments, ``%ptr`` and ``%offset``. It loads a 32-bit value from the address ``%ptr + %offset``, adds ``%ptr`` to that value and returns it. The constant folder specifically recognizes the form of this intrinsic and the constant initializers it may load from; if a loaded constant initializer is known to have the form ``i32 trunc(x - %ptr)``, the intrinsic call is folded to ``x``. LLVM provides that the calculation of such a constant initializer will not overflow at link time under the medium code model if ``x`` is an ``unnamed_addr`` function. However, it does not provide this guarantee for a constant initializer folded into a function body. This intrinsic can be used to avoid the possibility of overflows when loading from such a constant. Differential Revision: http://reviews.llvm.org/D18367 llvm-svn: 267223
76 lines
2.5 KiB
LLVM
76 lines
2.5 KiB
LLVM
; RUN: opt < %s -instsimplify -S | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@a = external global i8
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@b = external global i8
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@c1 = constant i32 trunc (i64 sub (i64 ptrtoint (i8* @a to i64), i64 ptrtoint (i32* @c1 to i64)) to i32)
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@c2 = constant [7 x i32] [i32 0, i32 0,
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i32 trunc (i64 sub (i64 ptrtoint (i8* @a to i64), i64 ptrtoint (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i32 0, i32 2) to i64)) to i32),
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i32 trunc (i64 sub (i64 ptrtoint (i8* @b to i64), i64 ptrtoint (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i32 0, i32 2) to i64)) to i32),
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i32 trunc (i64 add (i64 ptrtoint (i8* @b to i64), i64 ptrtoint (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i32 0, i32 2) to i64)) to i32),
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i32 trunc (i64 sub (i64 ptrtoint (i8* @b to i64), i64 1) to i32),
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i32 trunc (i64 sub (i64 0, i64 ptrtoint (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i32 0, i32 2) to i64)) to i32)
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]
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; CHECK: @f1
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define i8* @f1() {
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; CHECK: ret i8* @a
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* @c1 to i8*), i32 0)
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ret i8* %l
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}
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; CHECK: @f2
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define i8* @f2() {
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; CHECK: ret i8* @a
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i32 0)
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ret i8* %l
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}
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; CHECK: @f3
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define i8* @f3() {
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; CHECK: ret i8* @b
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%l = call i8* @llvm.load.relative.i64(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i64 4)
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ret i8* %l
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}
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; CHECK: @f4
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define i8* @f4() {
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; CHECK: ret i8* %
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i32 1)
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ret i8* %l
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}
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; CHECK: @f5
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define i8* @f5() {
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; CHECK: ret i8* %
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%l = call i8* @llvm.load.relative.i32(i8* zeroinitializer, i32 0)
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ret i8* %l
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}
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; CHECK: @f6
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define i8* @f6() {
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; CHECK: ret i8* %
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i32 8)
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ret i8* %l
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}
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; CHECK: @f7
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define i8* @f7() {
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; CHECK: ret i8* %
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i32 12)
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ret i8* %l
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}
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; CHECK: @f8
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define i8* @f8() {
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; CHECK: ret i8* %
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%l = call i8* @llvm.load.relative.i32(i8* bitcast (i32* getelementptr ([7 x i32], [7 x i32]* @c2, i64 0, i64 2) to i8*), i32 16)
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ret i8* %l
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}
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declare i8* @llvm.load.relative.i32(i8*, i32)
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declare i8* @llvm.load.relative.i64(i8*, i64)
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