emmettneyman added inline comments.
================
Comment at: clang/tools/clang-fuzzer/proto-to-llvm/loop_proto_to_llvm.cpp:127
+ << "define void @foo(i32* %a, i32* %b, i32* %c, i64 %s) {\n"
+ << "%1 = icmp sgt i64 %s, 0\n"
+ << "br i1 %1, label %start, label %end\n"
----------------
morehouse wrote:
> Should `%s` be signed? Do we want unsigned compare here?
I don't think it matters since `%s` will always be positive (it will always be
equal to
`kArraySize` from `input_arrays.h`).
================
Comment at: clang/tools/clang-fuzzer/proto-to-llvm/loop_proto_to_llvm.cpp:134
+ << "end:\n"
+ << "ret void\n"
<< "loop:\n"
----------------
morehouse wrote:
> Seems like the `endloop` label is unnecessary. Does this help vectorize? If
> not, lets get rid of unconditional jumps to the next line.
I initially had it this way since that's how `-emit-llvm` generated the code.
But it doesn't seem like it's necessary for loops to be vectorized upon further
inspection.
================
Comment at: clang/tools/clang-fuzzer/proto-to-llvm/loop_proto_to_llvm.cpp:138
<< x.statements()
- << "%z = add i64 1, %ct\n"
- << "store i64 %z, i64* %i\n"
- << "br label %loop\n\n"
- << "endloop:\n"
- << "ret void\n}\n";
+ << "%ctnew = add nuw nsw i64 %ct, 1\n"
+ << "%j = icmp eq i64 %ctnew, %s\n"
----------------
morehouse wrote:
> This will make overflow undefined... Isn't that the opposite of what we want?
> That will permit LLVM to assume overflow never happens and modify the code
> in new ways based on that assumption.
That's a good point. It probably won't matter since this addition will never
overflow (we're just starting at zero and incrementing by one). This is what
was generated by `-emit-llvm`. I'll remove it to reduce confusion.
Repository:
rC Clang
https://reviews.llvm.org/D50342
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