Evan Cheng ae16d6b972 SimplifyCFG has stopped duplicating returns into predecessors to canonicalize IR ... to have single return block (at least getting there) for optimizations. This is general goodness but it would prevent some tailcall optimizations. One specific case is code like this: int f1(void); int f2(void); int f3(void); int f4(void); int f5(void); int f6(void); int foo(int x) { switch(x) { case 1: return f1(); case 2: return f2(); case 3: return f3(); case 4: return f4(); case 5: return f5(); case 6: return f6(); } } => LBB0_2: ## %sw.bb callq _f1 popq %rbp ret LBB0_3: ## %sw.bb1 callq _f2 popq %rbp ret LBB0_4: ## %sw.bb3 callq _f3 popq %rbp ret This patch teaches codegenprep to duplicate returns when the return value is a phi and where the phi operands are produced by tail calls followed by an unconditional branch: sw.bb7: ; preds = %entry %call8 = tail call i32 @f5() nounwind br label %return sw.bb9: ; preds = %entry %call10 = tail call i32 @f6() nounwind br label %return return: %retval.0 = phi i32 [ %call10, %sw.bb9 ], [ %call8, %sw.bb7 ], ... [ 0, %entry ] ret i32 %retval.0 This allows codegen to generate better code like this: LBB0_2: ## %sw.bb jmp _f1 ## TAILCALL LBB0_3: ## %sw.bb1 jmp _f2 ## TAILCALL LBB0_4: ## %sw.bb3 jmp _f3 ## TAILCALL rdar://9147433 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127953 91177308-0d34-0410-b5e6-96231b3b80d8		2011-03-19 17:17:39 +00:00
..
Mangler.h	Remove std::string version of getNameWithPrefix.	2011-02-11 05:23:09 +00:00
SubtargetFeature.h	Merge System into Support.	2010-11-29 18:16:10 +00:00
Target.td	- Add "Bitcast" target instruction property for instructions which perform	2011-03-15 05:09:26 +00:00
TargetAsmBackend.h	Add createELFObjectTargetWriter method to TargetAsmBackend, which enables construction of non-standard ELFObjectWriters that can be used in MCJIT.	2011-03-09 18:44:41 +00:00
TargetAsmInfo.h	Rename TargetFrameInfo into TargetFrameLowering. Also, put couple of FIXMEs and fixes here and there.	2011-01-10 12:39:04 +00:00
TargetAsmLexer.h	Moved InstallLexer() from the X86-specific AsmLexer	2010-01-31 02:28:18 +00:00
TargetAsmParser.h	Introduce virtual ParseRegister method in TargetAsmParser.	2011-01-27 17:14:22 +00:00
TargetCallingConv.h	Inside the calling convention logic LocVT is always a simple	2010-11-03 11:35:31 +00:00
TargetCallingConv.td	Fix a couple of typos.	2010-08-27 21:38:11 +00:00
TargetData.h	Add TargetData::fitsInLegalInteger().	2011-03-16 00:13:28 +00:00
TargetELFWriterInfo.h	Jim Asked us to move DataLayout on ARM back to the most specialized classes. Do	2010-10-03 18:59:45 +00:00
TargetFrameLowering.h	Rename TargetFrameInfo into TargetFrameLowering. Also, put couple of FIXMEs and fixes here and there.	2011-01-10 12:39:04 +00:00
TargetInstrDesc.h	- Add "Bitcast" target instruction property for instructions which perform	2011-03-15 05:09:26 +00:00
TargetInstrInfo.h	Missing "virtual" keyword. Jakob's review.	2011-03-05 08:39:45 +00:00
TargetInstrItineraries.h	Various bits of framework needed for precise machine-level selection	2010-12-24 05:03:26 +00:00
TargetIntrinsicInfo.h	Reintroduce support for overloading target intrinsics	2009-11-05 03:19:08 +00:00
TargetJITInfo.h	Merge System into Support.	2010-11-29 18:16:10 +00:00
TargetLibraryInfo.h	Optimize fprintf -> iprintf if there are no floating point arguments	2011-03-03 14:20:22 +00:00
TargetLowering.h	SimplifyCFG has stopped duplicating returns into predecessors to canonicalize IR	2011-03-19 17:17:39 +00:00
TargetLoweringObjectFile.h	Delay the creation of eh_frame so that the user can change the defaults.	2011-01-23 05:43:40 +00:00
TargetMachine.h	Beginnings of MC-JIT code generation.	2011-03-18 22:48:41 +00:00
TargetOpcodes.h	Rename DBG_LABEL PROLOG_LABEL, because it's only used during prolog emission and	2010-07-16 22:20:36 +00:00
TargetOptions.h	Grammar.	2010-07-29 18:11:28 +00:00
TargetRegisterInfo.h	Re-commit 127368 and 127371. They are exonerated.	2011-03-10 00:16:32 +00:00
TargetRegistry.h	Add support for the --noexecstack option.	2011-01-23 17:55:27 +00:00
TargetSchedule.td	Comments about operand cycles and pipeline forwarding pathes.	2010-09-30 22:01:50 +00:00
TargetSelect.h	Add InitializeNativeAsmParser function.	2011-03-09 17:25:46 +00:00
TargetSelectionDAG.td	[AVX] Add INSERT_SUBVECTOR and support it on x86. This provides a	2011-01-26 19:13:22 +00:00
TargetSelectionDAGInfo.h	reimplement memcpy/memmove/memset lowering to use MachinePointerInfo	2010-09-21 05:40:29 +00:00
TargetSubtarget.h	Allow target to specify regclass for which antideps will only be broken along the critical path.	2009-11-13 19:52:48 +00:00