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author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-01-07 20:42:20 +0000 |
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committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-01-07 20:42:20 +0000 |
commit | eaff66a8950bb9ed76e830c4ded7e0b695ab6904 (patch) | |
tree | 83dd056fee7b677e7af5b72f924bf2e2930c5c8b /lib | |
parent | 53bf3ee82ba9fb6e6008b9752d4f8f4e71a4bfe4 (diff) | |
download | llvm-eaff66a8950bb9ed76e830c4ded7e0b695ab6904.tar.gz llvm-eaff66a8950bb9ed76e830c4ded7e0b695ab6904.tar.bz2 llvm-eaff66a8950bb9ed76e830c4ded7e0b695ab6904.tar.xz |
Revert 122959, it needs more thought. Add it back to README.txt with additional notes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123030 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r-- | lib/Target/README.txt | 22 | ||||
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineCalls.cpp | 4 |
2 files changed, 22 insertions, 4 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index d13ea736a1..5cc4fe027a 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -2009,6 +2009,28 @@ entry: //===---------------------------------------------------------------------===// +This code can be seen in viterbi: + + %64 = call noalias i8* @malloc(i64 %62) nounwind +... + %67 = call i64 @llvm.objectsize.i64(i8* %64, i1 false) nounwind + %68 = call i8* @__memset_chk(i8* %64, i32 0, i64 %62, i64 %67) nounwind + +llvm.objectsize.i64 should be taught about malloc/calloc, allowing it to +fold to %62. This is a security win (overflows of malloc will get caught) +and also a performance win by exposing more memsets to the optimizer. + +This occurs several times in viterbi. + +Note that this would change the semantics of @llvm.objectsize which by its +current definition always folds to a constant. We also should make sure that +we remove checking in code like + + char *p = malloc(strlen(s)+1); + __strcpy_chk(p, s, __builtin_objectsize(p, 0)); + +//===---------------------------------------------------------------------===// + This code (from Benchmarks/Dhrystone/dry.c): define i32 @Func1(i32, i32) nounwind readnone optsize ssp { diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp index ecd2243c35..bd451ebcac 100644 --- a/lib/Transforms/InstCombine/InstCombineCalls.cpp +++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp @@ -304,10 +304,6 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { if (Value *NElems = getMallocArraySize(MI, TD, true)) if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) Size = NElements->getZExtValue() * TD->getTypeAllocSize(MallocType); - - // If there is no offset we can just return the size passed to malloc. - if (Offset == 0) - return ReplaceInstUsesWith(CI, MI->getArgOperand(0)); } // Do not return "I don't know" here. Later optimization passes could |