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| author | Duncan P. N. Exon Smith <dexonsmith@apple.com> | 2014-06-12 21:16:19 +0000 |
|---|---|---|
| committer | Duncan P. N. Exon Smith <dexonsmith@apple.com> | 2014-06-12 21:16:19 +0000 |
| commit | 3fdfffbfa344858ce0ffb3dec9a997fb40584857 (patch) | |
| tree | 437cb411e972aa1dce985c25f404f8255b5e3ed6 /test | |
| parent | 00c3986254430289472ad839c86dae252139b89c (diff) | |
| download | llvm-3fdfffbfa344858ce0ffb3dec9a997fb40584857.tar.gz llvm-3fdfffbfa344858ce0ffb3dec9a997fb40584857.tar.bz2 llvm-3fdfffbfa344858ce0ffb3dec9a997fb40584857.tar.xz | |
GVN: Enable value forwarding for calloc
Enable value forwarding for loads from `calloc()` without an intervening
store.
This change extends GVN to handle the following case:
%1 = tail call noalias i8* @calloc(i64 1, i64 4)
%2 = bitcast i8* %1 to i32*
; This load is trivially constant zero
%3 = load i32* %2, align 4
This is analogous to the handling for `malloc()` in the same places.
`malloc()` returns `undef`; `calloc()` returns a zero value. Note that
it is correct to return zero even for out of bounds GEPs since the
result of such a GEP would be undefined.
Patch by Philip Reames!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210828 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test')
| -rw-r--r-- | test/Transforms/GVN/calloc-load-removal.ll | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/test/Transforms/GVN/calloc-load-removal.ll b/test/Transforms/GVN/calloc-load-removal.ll new file mode 100644 index 0000000000..2dde5b7b41 --- /dev/null +++ b/test/Transforms/GVN/calloc-load-removal.ll @@ -0,0 +1,25 @@ +; RUN: opt -S -basicaa -gvn < %s | FileCheck %s +; RUN: opt -S -basicaa -gvn -disable-simplify-libcalls < %s | FileCheck %s -check-prefix=CHECK_NO_LIBCALLS +; Check that loads from calloc are recognized as being zero. + +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" + +; Function Attrs: nounwind uwtable +define i32 @test1() { + %1 = tail call noalias i8* @calloc(i64 1, i64 4) + %2 = bitcast i8* %1 to i32* + ; This load is trivially constant zero + %3 = load i32* %2, align 4 + ret i32 %3 + +; CHECK-LABEL: @test1( +; CHECK-NOT: %3 = load i32* %2, align 4 +; CHECK: ret i32 0 + +; CHECK_NO_LIBCALLS-LABEL: @test1( +; CHECK_NO_LIBCALLS: load +; CHECK_NO_LIBCALLS: ret i32 % + +} + +declare noalias i8* @calloc(i64, i64) |