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| author | Chandler Carruth <chandlerc@gmail.com> | 2012-03-12 11:19:31 +0000 |
|---|---|---|
| committer | Chandler Carruth <chandlerc@gmail.com> | 2012-03-12 11:19:31 +0000 |
| commit | fc72ae613afd7ca2526bb66156bafe8b0054cb3b (patch) | |
| tree | c25757bf86fcac9b4b369729c274ef0be0e682ba /test/Transforms/InstSimplify | |
| parent | 747cccf0dc345ab63894ce498233868cf110b717 (diff) | |
| download | llvm-fc72ae613afd7ca2526bb66156bafe8b0054cb3b.tar.gz llvm-fc72ae613afd7ca2526bb66156bafe8b0054cb3b.tar.bz2 llvm-fc72ae613afd7ca2526bb66156bafe8b0054cb3b.tar.xz | |
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
Diffstat (limited to 'test/Transforms/InstSimplify')
| -rw-r--r-- | test/Transforms/InstSimplify/ptr_diff.ll | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/test/Transforms/InstSimplify/ptr_diff.ll b/test/Transforms/InstSimplify/ptr_diff.ll new file mode 100644 index 0000000000..013964ccfe --- /dev/null +++ b/test/Transforms/InstSimplify/ptr_diff.ll @@ -0,0 +1,33 @@ +; 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 + + %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 +} + +define i64 @ptrdiff2(i8* %ptr) { +; CHECK: @ptrdiff2 +; CHECK-NEXT: ret i64 42 + + %first1 = getelementptr i8* %ptr, i32 0 + %first2 = getelementptr i8* %first1, i32 1 + %first3 = getelementptr i8* %first2, i32 2 + %first4 = getelementptr i8* %first3, i32 4 + %last1 = getelementptr i8* %first2, i32 48 + %last2 = getelementptr i8* %last1, i32 8 + %last3 = getelementptr i8* %last2, i32 -4 + %last4 = getelementptr i8* %last3, i32 -4 + %first.int = ptrtoint i8* %first4 to i64 + %last.int = ptrtoint i8* %last4 to i64 + %diff = sub i64 %last.int, %first.int + ret i64 %diff +} |