[LLVMbugs] [Bug 21473] New: [CFGSimplification] Generate none optimized constant ADD operations

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21473

            Bug ID: 21473
           Summary: [CFGSimplification] Generate none optimized constant
                    ADD operations
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: Hao.Liu at arm.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 13285
  --> http://llvm.org/bugs/attachment.cgi?id=13285&action=edit
CFGSimplification Test Case

To reproduce by following command lines:
clang -O3 -S -emit-llvm simple.c
llc -march=aarch64 < simple.ll -print-after-all

We can see that in AArch64 backend, CFGSimplification generate none optimized
ADDs as follows:
...
%inc.1.1 = add nsw i32 2, 1
...
%inc.2.1 = add nsw i32 %inc.1.1, 1
...
%inc.1.2 = add nsw i32 %inc.1.1, 2
...

Such ADDs can be replaced by constants 3, 4, 5.

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