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llvm-6502/test/Transforms/InstSimplify/ptr_diff.ll

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Teach instsimplify how to constant fold pointer differences. Typically instcombine has handled this, but pointer differences show up in several contexts where we would like to get constant folding, and cannot afford to run instcombine. Specifically, I'm working on improving the constant folding of arguments used in inline cost analysis with instsimplify. Doing this in instsimplify implies some algorithm changes. We have to handle multiple layers of all-constant GEPs because instsimplify cannot fold them into a single GEP the way instcombine can. Also, we're only interested in all-constant GEPs. The result is that this doesn't really replace the instcombine logic, it's just complimentary and focused on constant folding. Reviewed on IRC by Benjamin Kramer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152555 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-12 11:19:31 +00:00
; RUN: opt < %s -instsimplify -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i64 @ptrdiff1(i8* %ptr) {
; CHECK: @ptrdiff1
; CHECK-NEXT: ret i64 42
Switch the pointer-difference simplification logic to only work with inbounds GEPs. This isn't really necessary for simplifying pointer differences, but I'm planning to re-use the same code to simplify pointer comparisons where it is necessary. Since real code almost exclusively uses inbounds GEPs, it doesn't seem worth it to support the extra complexity of turning it on and off. If anyone would like that back, feel free to shout. Note that instcombine will still catch any of these patterns. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153418 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-25 20:43:07 +00:00
%first = getelementptr inbounds i8* %ptr, i32 0
%last = getelementptr inbounds i8* %ptr, i32 42
Teach instsimplify how to constant fold pointer differences. Typically instcombine has handled this, but pointer differences show up in several contexts where we would like to get constant folding, and cannot afford to run instcombine. Specifically, I'm working on improving the constant folding of arguments used in inline cost analysis with instsimplify. Doing this in instsimplify implies some algorithm changes. We have to handle multiple layers of all-constant GEPs because instsimplify cannot fold them into a single GEP the way instcombine can. Also, we're only interested in all-constant GEPs. The result is that this doesn't really replace the instcombine logic, it's just complimentary and focused on constant folding. Reviewed on IRC by Benjamin Kramer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152555 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-12 11:19:31 +00:00
%first.int = ptrtoint i8* %first to i64
%last.int = ptrtoint i8* %last to i64
%diff = sub i64 %last.int, %first.int
ret i64 %diff
}
define i64 @ptrdiff2(i8* %ptr) {
; CHECK: @ptrdiff2
; CHECK-NEXT: ret i64 42
Switch the pointer-difference simplification logic to only work with inbounds GEPs. This isn't really necessary for simplifying pointer differences, but I'm planning to re-use the same code to simplify pointer comparisons where it is necessary. Since real code almost exclusively uses inbounds GEPs, it doesn't seem worth it to support the extra complexity of turning it on and off. If anyone would like that back, feel free to shout. Note that instcombine will still catch any of these patterns. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153418 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-25 20:43:07 +00:00
%first1 = getelementptr inbounds i8* %ptr, i32 0
%first2 = getelementptr inbounds i8* %first1, i32 1
%first3 = getelementptr inbounds i8* %first2, i32 2
%first4 = getelementptr inbounds i8* %first3, i32 4
%last1 = getelementptr inbounds i8* %first2, i32 48
%last2 = getelementptr inbounds i8* %last1, i32 8
%last3 = getelementptr inbounds i8* %last2, i32 -4
%last4 = getelementptr inbounds i8* %last3, i32 -4
Teach instsimplify how to constant fold pointer differences. Typically instcombine has handled this, but pointer differences show up in several contexts where we would like to get constant folding, and cannot afford to run instcombine. Specifically, I'm working on improving the constant folding of arguments used in inline cost analysis with instsimplify. Doing this in instsimplify implies some algorithm changes. We have to handle multiple layers of all-constant GEPs because instsimplify cannot fold them into a single GEP the way instcombine can. Also, we're only interested in all-constant GEPs. The result is that this doesn't really replace the instcombine logic, it's just complimentary and focused on constant folding. Reviewed on IRC by Benjamin Kramer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152555 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-12 11:19:31 +00:00
%first.int = ptrtoint i8* %first4 to i64
%last.int = ptrtoint i8* %last4 to i64
%diff = sub i64 %last.int, %first.int
ret i64 %diff
}
Switch the pointer-difference simplification logic to only work with inbounds GEPs. This isn't really necessary for simplifying pointer differences, but I'm planning to re-use the same code to simplify pointer comparisons where it is necessary. Since real code almost exclusively uses inbounds GEPs, it doesn't seem worth it to support the extra complexity of turning it on and off. If anyone would like that back, feel free to shout. Note that instcombine will still catch any of these patterns. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153418 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-25 20:43:07 +00:00
define i64 @ptrdiff3(i8* %ptr) {
; Don't bother with non-inbounds GEPs.
; CHECK: @ptrdiff3
; CHECK: getelementptr
; CHECK: sub
; CHECK: ret
%first = getelementptr i8* %ptr, i32 0
%last = getelementptr i8* %ptr, i32 42
%first.int = ptrtoint i8* %first to i64
%last.int = ptrtoint i8* %last to i64
%diff = sub i64 %last.int, %first.int
ret i64 %diff
}
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