Souper: A Synthesizing Superoptimizer for LLVM

4PVQFS "4ZOUIFTJ[JOH4VQFSPQUJNJ[FSGPS--7. 1SFTFOUFECZ)BSMBO)BTLJOT #Z4BTOBVTLBT $IFO $PMMJOHCPVSOF ,FUFNB 5BOFKB BOE3FHFIS

8IBUJT--7. ↟ 1PQVMBSTFUPGMJCSBSJFTGPSDPNQJMFST ↟ %FGJOFTBOJOUFSNFEJBUFCFUXFFOIJHIMFWFMDPEFBOENBDIJOFDPEF ↟ --7.*3 ↟ 6TFEBTUIFCBDLFOEGPSEP[FOTPGDPNQJMFST ↟
$MBOH 3VTU 4XJGU $SZTUBM /JN 5SJMM ↟ .BJOCFOFGJU ↟ $PNNPOMBOHVBHF→ DSPTTDPNQJMBUJPO PQUJNJ[BUJPOT WFSJGJDBUJPOGPSGSFF

--7.*OUFSNFEJBUF3FQSFTFOUBUJPO *3 ↟ )JHIMFWFM"TTFNCMZMBOHVBHF ↟ 'VODUJPOT NFUBEBUB UZQFT ↟ 'VMMZTUBUJDBMMZUZQFE
↟ 4UBUJD4JOHMF"TTJHONFOUGPSN ↟ *OGJOJUFSFHJTUFST BTTJHOFEPODF

int plusOne(int n) { return n + 1; } --7.*OUFSNFEJBUF3FQSFTFOUBUJPO
*3 ↟ )JHIMFWFM"TTFNCMZMBOHVBHF ↟ 'VODUJPOT NFUBEBUB UZQFT ↟ 'VMMZTUBUJDBMMZUZQFE ↟ 4UBUJD4JOHMF"TTJHONFOUGPSN ↟ *OGJOJUFSFHJTUFST BTTJHOFEPODF

define i32 @plusOne(i32 %n) { entry: %0 = add i32
%n, i32 1 ret i32 %0 } int plusOne(int n) { return n + 1; } --7.*OUFSNFEJBUF3FQSFTFOUBUJPO *3 ↟ )JHIMFWFM"TTFNCMZMBOHVBHF ↟ 'VODUJPOT NFUBEBUB UZQFT ↟ 'VMMZTUBUJDBMMZUZQFE ↟ 4UBUJD4JOHMF"TTJHONFOUGPSN ↟ *OGJOJUFSFHJTUFST BTTJHOFEPODF

*OUSPEVDUJPOUP4PVQFS ↟ 0QUJNJ[BUJPO0SJFOUFE*3 ↟ %JTDPWFSTPQUJNJ[BUJPOTVTJOH UFDIOJRVFTGSPNWFSJGJDBUJPO ↟ --7.*3JTMPXFSFEUP4PVQFS*3 ↟ )BTNPSFSFTUSJDUFETFNBOUJDT
↟ 4VQQPSUTBTVCTFUPG--7. GFBUVSFT define i32 @plusOne(i32 %n) { entry: %0 = add i32 %n, i32 1 ret i32 %0 } %n: i32 = var %0 = add %n 1 infer %0 int plusOne(int n) { return n + 1; }

4PVQFS*3 ↟ 44"GPSNXJUIOPDPOUSPMGMPX ↟ $POEJUJPOBMEFQFOEFODJFTWJBQBUIDPOEJUJPOT ↟ *OUFHFSTDBMBSTVCTFUPG--7.PQFSBUJPOT ↟ --7.JTMPXFSFEUP4PVQFS*3 UIFOPQUJNJ[BUJPOT
BSFTPMWFE

4VQFSPQUJNJ[BUJPO ↟ 0QUJNJ[BUJPO→ .BLFDPEFGBTUFSPSNPSFPQUJNBM ↟ 4VQFSPQUJNJ[BUJPO→ .BLFDPEFQFSGFDUMZGBTUBOEPQUJNBM ↟ 4VQFSPQUJNJ[BUJPO→ "VUPNBUJDBMMZEJTDPWFSPQUJNJ[BUJPOT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ 1SPCMFN ↟ (JWFOB-)4 GJOEB3)4UIBUQFSGPSNTJEFOUJDBMMZ ↟ 5ZQJDBMPQUJNJ[BUJPO ↟ $POTUSBJOFETFUPGMPXFSJOHSVMFT
↟ .BUDIQBUUFSOT BEKVTUJOHDPEFJGQSPGJUBCMF

↟ .BUDIQBUUFSOT BEKVTUJOHDPEFJGQSPGJUBCMF -)4 %0 = add %n, 10: i32 %1 = add %0, 1: i32

↟ .BUDIQBUUFSOT BEKVTUJOHDPEFJGQSPGJUBCMF -)4 3)4 %0 = add %n, 10: i32 %1 = add %0, 1: i32 %0 = add %n, 11: i32

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ /BïWF4VQFS0QUJNJ[BUJPO ↟ 4ZOUIFTJ[FBSCJUSBSZ3)4FTVOUJMXFGJOEBNBUDI ↟ .BUDINVTUZJFMETBNFSFTVMUGPSBMMJOQVUT ↟ /POEFUFSNJOJTUJD ↟
7FSZFYQFOTJWFBOEUJNFDPOTVNJOH ↟ 3FRVJSFTQPUFOUJBMMZJOGJOJUF4.5TPMWFT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ $PVOUFS&YBNQMF(VJEFE*OEVDUJWF4ZOUIFTJT ↟ %FTDSJCFEJOSynthesis of loop-free programsCZ(VMXBOJ FUBM ↟
%FDPOTUSVDUUIFQSPHSBNJOUPBEFQFOEFODZHSBQI ↟ 5XP4.54PMWFT *TUIFSFBTFUPGSFMBUJPOTIJQTCFUXFFOWBMVFTTVDIUIBUBMM DPOTUSBJOUTBSFTBUJTGJFE %PFTUIJTOFX-)4NBUDIUIF3)4GPSBMMJOQVUT

4PVQFST"QQSPBDI -PXFS--7.*3UP4PVQFS*3 ↟ 8PSLTCBDLXBSETUISPVHIUIF$'(UPTZOUIFTJ[FQBUIDPOEJUJPOT 4ZOUIFTJ[F4.5-*#GPSNVMBFGPSFBDI4PVQFSGVODUJPO 'JSTUQBTT HFOFSBUFEFQFOEFODZHSBQI
4FDPOEQBTT WFSJGZFRVJWBMFODF 6TFSFTVMUTUPIBOEXSJUFOFX--7.PQUJNJ[BUJPOT 3FQFBUPODF--7.VQEBUFTUPEJTDPWFSGVSUIFSPQUJNJ[BUJPOT

0QUJNJ[BUJPO&YBNQMFT %0: i64 = var %1: i64 = mul %0,
2654435761: i64 %2: i64 = and %1, 1: i64 %3: i1 = ne %2, 0: i64 infer %3

0QUJNJ[BUJPO&YBNQMFT %0: i64 = var %1: i64 = mul %0,
2654435761: i64 %2: i64 = and %1, 1: i64 %3: i1 = ne %2, 0: i64 infer %3 %4: i1 = trunc %0 result %4 .VMUJQMJDBUJPOXJUIBOPEEOVNCFSXJMMBMXBZTCF PEEJGUIFPSJHJOBMOVNCFSJTPEE

0QUJNJ[BUJPO&YBNQMFT %0: i32 = var %1: i32 = xor %0,
4294967295: i32 %2: i32 = and %1, 8: i32 infer %2

0QUJNJ[BUJPO&YBNQMFT %0: i32 = var %1: i32 = xor %0,
4294967295: i32 %2: i32 = and %1, 8: i32 infer %2 %3: i32 = and 8: i32, %0 %4: i32 = xor 8: i32, %3 result %4 *OTUFBEPGJOWFSUJOHBCJUWBMVFBOEUFTUJOHCJU NBTLUPHFU(%0 & 0b100)BOEUFTUUIFCJUWBMVF 4PVQFSDBVHIUUIJTCZMVDL

0QUJNJ[BUJPO&YBNQMFT %0: i8 = var %1: i8 = lshr %0,
3: i8 %2: i1 = eq %1, 0: i8 infer %2

0QUJNJ[BUJPO&YBNQMFT %0: i8 = var %1: i8 = lshr %0,
3: i8 %2: i1 = eq %1, 0: i8 infer %2 %3: i32 = ult %0, 8: i32 result %3 "WBMVFTIJGUFESJHIUUJNFTDBOCF[FSPPOMZJGJUJT TNBMMFSUIBO͌

0QUJNJ[BUJPO&YBNQMFT %P[FOTNPSFFYBNQMFTJOUIFQBQFS

1PTTJCJMJUJFT ↟ 4VQFSPQUJNJ[BUJPOXJMMTJHOJGJDBOUMZJNQSPWFFYJTUJOHPQUJNJ[BUJPOT ↟ 4PVQFSIBTBMSFBEZJOGPSNFETFWFSBM--7.PQUJNJ[BUJPOT NPTUEFBMJOH XJUICJUNBOJQVMBUJPO ↟ "QQMZJOHWFSJGJDBUJPOUFDIOJRVFTFOBCMFTJODSFEJCMFPQUJNJ[BUJPOT ↟
4JODF--7.JTDPNNPODVSSFODZ BMM--7.DPNQJMFSTCFOFGJUGSPN4PVQFS ↟ *ODPSQPSBUJOHUIJTJOUPPUIFSDPNQJMFSTXJMMJNQSPWFDPNQJMFSTPWFSBMM ↟ $PNQFUJUJPOJTIFBMUIZ

5IBOL:PV 2VFTUJPOT

Souper: A Synthesizing Superoptimizer for LLVM

Souper: A Synthesizing Superoptimizer for LLVM

Harlan

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4PVQFS "4ZOUIFTJ[JOH4VQFSPQUJNJ[FSGPS--7. 1SFTFOUFECZ)BSMBO)BTLJOT #Z4BTOBVTLBT $IFO $PMMJOHCPVSOF ,FUFNB 5BOFKB BOE3FHFIS

8IBUJT--7. ↟ 1PQVMBSTFUPGMJCSBSJFTGPSDPNQJMFST ↟ %FGJOFTBOJOUFSNFEJBUFCFUXFFOIJHIMFWFMDPEFBOENBDIJOFDPEF ↟ --7.*3 ↟ 6TFEBTUIFCBDLFOEGPSEP[FOTPGDPNQJMFST ↟

--7.OUFSNFEJBUF3FQSFTFOUBUJPO 3 ↟ )JHIMFWFM"TTFNCMZMBOHVBHF ↟ 'VODUJPOT NFUBEBUB UZQFT ↟ 'VMMZTUBUJDBMMZUZQFE

int plusOne(int n) { return n + 1; } --7.*OUFSNFEJBUF3FQSFTFOUBUJPO

define i32 @plusOne(i32 %n) { entry: %0 = add i32

OUSPEVDUJPOUP4PVQFS ↟ 0QUJNJ[BUJPO0SJFOUFE3 ↟ %JTDPWFSTPQUJNJ[BUJPOTVTJOH UFDIOJRVFTGSPNWFSJGJDBUJPO ↟ --7.3JTMPXFSFEUP4PVQFS3 ↟ )BTNPSFSFTUSJDUFETFNBOUJDT

4PVQFS3 ↟ 44"GPSNXJUIOPDPOUSPMGMPX ↟ $POEJUJPOBMEFQFOEFODJFTWJBQBUIDPOEJUJPOT ↟ OUFHFSTDBMBSTVCTFUPG--7.PQFSBUJPOT ↟ --7.JTMPXFSFEUP4PVQFS*3 UIFOPQUJNJ[BUJPOT

4VQFSPQUJNJ[BUJPO ↟ 0QUJNJ[BUJPO→ .BLFDPEFGBTUFSPSNPSFPQUJNBM ↟ 4VQFSPQUJNJ[BUJPO→ .BLFDPEFQFSGFDUMZGBTUBOEPQUJNBM ↟ 4VQFSPQUJNJ[BUJPO→ "VUPNBUJDBMMZEJTDPWFSPQUJNJ[BUJPOT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ 1SPCMFN ↟ (JWFOB-)4 GJOEB3)4UIBUQFSGPSNTJEFOUJDBMMZ ↟ 5ZQJDBMPQUJNJ[BUJPO ↟ $POTUSBJOFETFUPGMPXFSJOHSVMFT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ 1SPCMFN ↟ (JWFOB-)4 GJOEB3)4UIBUQFSGPSNTJEFOUJDBMMZ ↟ 5ZQJDBMPQUJNJ[BUJPO ↟ $POTUSBJOFETFUPGMPXFSJOHSVMFT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ 1SPCMFN ↟ (JWFOB-)4 GJOEB3)4UIBUQFSGPSNTJEFOUJDBMMZ ↟ 5ZQJDBMPQUJNJ[BUJPO ↟ $POTUSBJOFETFUPGMPXFSJOHSVMFT

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ /BïWF4VQFS0QUJNJ[BUJPO ↟ 4ZOUIFTJ[FBSCJUSBSZ3)4FTVOUJMXFGJOEBNBUDI ↟ .BUDINVTUZJFMETBNFSFTVMUGPSBMMJOQVUT ↟ /POEFUFSNJOJTUJD ↟

4ZOUIFTJ[JOH0QUJNJ[BUJPOT ↟ $PVOUFS&YBNQMF(VJEFE*OEVDUJWF4ZOUIFTJT ↟ %FTDSJCFEJOSynthesis of loop-free programsCZ(VMXBOJ FUBM ↟

4PVQFST"QQSPBDI -PXFS--7.3UP4PVQFS3 ↟ 8PSLTCBDLXBSETUISPVHIUIF$'(UPTZOUIFTJ[FQBUIDPOEJUJPOT 4ZOUIFTJ[F4.5-*#GPSNVMBFGPSFBDI4PVQFSGVODUJPO 'JSTUQBTT HFOFSBUFEFQFOEFODZHSBQI

0QUJNJ[BUJPO&YBNQMFT %0: i64 = var %1: i64 = mul %0,

0QUJNJ[BUJPO&YBNQMFT %0: i64 = var %1: i64 = mul %0,

0QUJNJ[BUJPO&YBNQMFT %0: i32 = var %1: i32 = xor %0,

0QUJNJ[BUJPO&YBNQMFT %0: i32 = var %1: i32 = xor %0,

0QUJNJ[BUJPO&YBNQMFT %0: i8 = var %1: i8 = lshr %0,

0QUJNJ[BUJPO&YBNQMFT %0: i8 = var %1: i8 = lshr %0,

0QUJNJ[BUJPO&YBNQMFT %P[FOTNPSFFYBNQMFTJOUIFQBQFS

1PTTJCJMJUJFT ↟ 4VQFSPQUJNJ[BUJPOXJMMTJHOJGJDBOUMZJNQSPWFFYJTUJOHPQUJNJ[BUJPOT ↟ 4PVQFSIBTBMSFBEZJOGPSNFETFWFSBM--7.PQUJNJ[BUJPOT NPTUEFBMJOH XJUICJUNBOJQVMBUJPO ↟ "QQMZJOHWFSJGJDBUJPOUFDIOJRVFTFOBCMFTJODSFEJCMFPQUJNJ[BUJPOT ↟

5IBOL:PV 2VFTUJPOT