[llvm-dev] PPC64 Disassembler (original) (raw)

Leonardo Bianconi via llvm-dev llvm-dev at lists.llvm.org
Thu Nov 30 01:45:49 PST 2017

Hi Sean,

Yes, it is. It has the method "isBranch()", which checks the "Flags" variable if the branch bit is set.

Leonardo Bianconi.

-----Original Message----- From: Sean Fertile [mailto:sd.fertile at gmail.com] Sent: quarta-feira, 29 de novembro de 2017 23:31 To: Leonardo Bianconi <leonardo.bianconi at eldorado.org.br> Cc: llvm-dev at lists.llvm.org Subject: Re: [llvm-dev] PPC64 Disassembler

Hello Leonardo,

What is the opcode of the MCInstrDesc?

Sean

On Wed, Nov 29, 2017 at 1:48 PM, Leonardo Bianconi via llvm-dev <llvm-dev at lists.llvm.org> wrote:

Hi all,

I’m working on lldb to make it available to ppc64le, but the “step over” is not working for some cases. When debugging, I can see that the disassembler analyze some instructions forward, looking for a branch instruction (llvm/tools/lldb/source/Plugins/Disassembler/llvm/DisassemblerLLVMC.cp p:87 – “const bool canbranch = mcdisasmptr->CanBranch(inst);”), while trying to set the next breakpoint. On this case, the instruction is the “bne cr7,0x2000092c”, which is a branch, but at llvm/lib/MC/MCInstrDesc.cpp:35 – “if (isBranch() || isCall() || isReturn() || isIndirectBranch())” it returns false, making lldb do not set the correct breakpoint, so the execution does not stop at next line, which should be the “step over” behavior. The variable “Flags” for the disassembled instruction does not have the branch flag. I have tried to change the file “/lib/Target/PowerPC/PPCInstrInfo.td”, adding “isBranch = 1” for the instruction "bc 4, bi,bi, bi,dst", but had not effect. Comparing with x8664, building the same cpp file, the instruction “jne 0x4005eb” has the branch flag, which identifies it as a branch instruction. Where is the definition that an instruction is a branch? Is it a bug? Thanks!

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