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| author | Evgeniy Stepanov <eugeni.stepanov@gmail.com> | 2013-10-30 17:44:22 +0000 |
|---|---|---|
| committer | Evgeniy Stepanov <eugeni.stepanov@gmail.com> | 2013-10-30 17:44:22 +0000 |
| commit | 9afa4528e02c1531885ccaad903acd28dda54556 (patch) | |
| tree | b0b7728521d99ad0ca6fb268c2c1add6e389bf51 | |
| parent | a263425653a44ea823e2e071a7d1ab686b47c570 (diff) | |
| download | compiler-rt-9afa4528e02c1531885ccaad903acd28dda54556.tar.gz compiler-rt-9afa4528e02c1531885ccaad903acd28dda54556.tar.bz2 compiler-rt-9afa4528e02c1531885ccaad903acd28dda54556.tar.xz | |
[msandr] Add check-before-write optimization.
Replace blind store with check-before-store to avoid unnecessary memory stores.
Patch by Qin Zhao.
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@193703 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/msandr/msandr.cc | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/lib/msandr/msandr.cc b/lib/msandr/msandr.cc index c1faec2e..6c9d7c67 100644 --- a/lib/msandr/msandr.cc +++ b/lib/msandr/msandr.cc @@ -309,17 +309,31 @@ void InstrumentMops(void *drcontext, instrlist_t *bb, instr_t *instr, opnd_t op, opnd_size_t op_size = opnd_get_size(op); CHECK(op_size != OPSZ_NA); uint access_size = opnd_size_in_bytes(op_size); - // TODO: optimize it with check-before-write if (access_size <= 4 || op_size == OPSZ_PTR /* x64 support sign extension */) { - PRE(instr, - mov_st(drcontext, opnd_create_base_disp(R1, DR_REG_NULL, 0, 0, op_size), - opnd_create_immed_int((ptr_int_t) 0, - (op_size == OPSZ_PTR) ? OPSZ_4 : op_size))); + instr_t *label = INSTR_CREATE_label(drcontext); + opnd_t immed; + if (op_size == OPSZ_PTR || op_size == OPSZ_4) + immed = OPND_CREATE_INT32(0); + else + immed = opnd_create_immed_int((ptr_int_t) 0, op_size); + // we check if target is 0 before write to reduce unnecessary memory stores. + PRE(instr, cmp(drcontext, + opnd_create_base_disp(R1, DR_REG_NULL, 0, 0, op_size), + immed)); + PRE(instr, jcc(drcontext, OP_je, opnd_create_instr(label))); + PRE(instr, mov_st(drcontext, + opnd_create_base_disp(R1, DR_REG_NULL, 0, 0, op_size), + immed)); + PREF(instr, label); } else { // FIXME: tail? for (uint ofs = 0; ofs < access_size; ofs += 4) { - PRE(instr, - mov_st(drcontext, OPND_CREATE_MEM32(R1, ofs), OPND_CREATE_INT32(0))); + instr_t *label = INSTR_CREATE_label(drcontext); + opnd_t immed = OPND_CREATE_INT32(0); + PRE(instr, cmp(drcontext, OPND_CREATE_MEM32(R1, ofs), immed)); + PRE(instr, jcc(drcontext, OP_je, opnd_create_instr(label))); + PRE(instr, mov_st(drcontext, OPND_CREATE_MEM32(R1, ofs), immed)); + PREF(instr, label) } } |