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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 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267223 91177308-0d34-0410-b5e6-96231b3b80d8
20 lines
677 B
LLVM
20 lines
677 B
LLVM
; RUN: opt < %s -instsimplify -S | FileCheck %s
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
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target triple = "i386-unknown-linux-gnu"
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@a = external global i8
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@c1 = constant [3 x i32] [i32 0, i32 0,
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i32 sub (i32 ptrtoint (i8* @a to i32), i32 ptrtoint (i32* getelementptr ([3 x i32], [3 x i32]* @c1, i32 0, i32 2) 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* getelementptr ([3 x i32], [3 x i32]* @c1, i32 0, i32 2) to i8*), i32 0)
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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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