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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi Jingyue,<span style='font-size:11.0pt'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When I look at the cost model of GEP for the following IR on AArch64, I have a question about getGEPCost() that you implemented in 2015.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>%"class.boost::array.16" = type { [24 x i32] }<o:p></o:p></p><p class=MsoNormal>%arrayidx.i17 = getelementptr inbounds %"class.boost::array.16", %"class.boost::array.16"* %moves, i64 0, i32 0, i64 %conv7 <o:p></o:p></p><p class=MsoNormal>store i32 %add, i32* %arrayidx.i17, align 4, !tbaa !18<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>GEP can be folded into the Store and the assembly is simple as <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>str w24, [x20, x8, lsl #2]<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>But the cost model says the GEP cannot be folded. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>getGEPCost() calls isLegalAddressingMode() in the following way to check the GEP can be folded or not<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>static_cast<T *>(this)->isLegalAddressingMode( <o:p></o:p></p><p class=MsoNormal> PointerType::get(*GTI, AS), const_cast<GlobalValue *>(BaseGV),<o:p></o:p></p><p class=MsoNormal> BaseOffset, HasBaseReg, Scale, AS)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>It seems to me that the first argument should be *<b>GTI, rather than PointerType::get(</b>*GTI, AS). In my example, *GTI is i32 and <b>PointerType::get(</b>*GTI, AS) is i32*. The current implementation fails the last check of AArch64TargetLowering::isLegalAddressingMode() which is <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>AM.Scale > 0 && (uint64_t)AM.Scale == NumBytes<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Because AM.Scale = 4 and NumBytes = 8<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I checked the implementation of isLegalAddressingMode() in several different backends and several other passes (LoopStrengthReduce and CodeGenPrepare) that call isLegalAddressingMode(). It seems my understanding is correct. Would you please take a look at this?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>A simplified test case can be<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>gep.ll<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>%"class.boost::array.16" = type { [24 x i32] }<o:p></o:p></p><p class=MsoNormal>define void @test_geps(%"class.boost::array.16"* %moves, i64 %conv7) {<o:p></o:p></p><p class=MsoNormal> %arrayidx.i17 = getelementptr inbounds %"class.boost::array.16", %"class.boost::array.16"* %moves, i64 0, i32 0, i64 %conv7<o:p></o:p></p><p class=MsoNormal> ret void<o:p></o:p></p><p class=MsoNormal>}<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Just run it with following command and the cost of GEP should be 0.<o:p></o:p></p><p class=MsoNormal>opt -cost-model -analyze -mtriple=aarch64-gnu-linux gep.ll<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thank you in advance,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Haicheng Wu<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Employee of Qualcomm Datacenter Technologies, Inc.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.<o:p></o:p></span></p></div></body></html>