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
..
ADCE.cpp
BasicBlockPlacement.cpp
CMakeLists.txt	Unbreak CMake build.	2011-02-28 23:56:33 +00:00
CodeGenPrepare.cpp	SimplifyCFG has stopped duplicating returns into predecessors to canonicalize IR	2011-03-19 17:17:39 +00:00
ConstantProp.cpp
CorrelatedValuePropagation.cpp
DCE.cpp
DeadStoreElimination.cpp	Give GetUnderlyingObject a TargetData, to keep it in sync	2011-01-24 18:53:32 +00:00
EarlyCSE.cpp	Duncan deftly points out that readnone functions aren't	2011-01-03 23:38:13 +00:00
GVN.cpp	Give GetUnderlyingObject a TargetData, to keep it in sync	2011-01-24 18:53:32 +00:00
IndVarSimplify.cpp	Remove TargetData and ValueTracking includes. I didn't mean for them to sneak in my last checkin.	2011-03-18 00:36:39 +00:00
JumpThreading.cpp	prevent jump threading from merging blocks when their address is	2011-02-18 04:43:06 +00:00
LICM.cpp	While sinking an instruction, do not lose llvm.dbg.value intrinsic.	2011-03-08 03:06:19 +00:00
LoopDeletion.cpp	Make LoopDeletion work on loops with multiple edges, as long as the incoming	2011-02-22 22:25:39 +00:00
LoopIdiomRecognize.cpp	Added SCEV::NoWrapFlags to manage unsigned, signed, and self wrap	2011-03-14 16:50:06 +00:00
LoopInstSimplify.cpp	LoopInstSimplify preserves ScalarEvolution.	2011-02-11 06:08:25 +00:00
LoopRotation.cpp	Do not hoist @llvm.dbg.value. Here, @llvm.dbg.value is "referring" a value that is modified inside loop.	2011-02-14 23:03:23 +00:00
LoopStrengthReduce.cpp	Added SCEV::NoWrapFlags to manage unsigned, signed, and self wrap	2011-03-14 16:50:06 +00:00
LoopUnrollPass.cpp	Remove dead code, that I apparently wrote a while back. We seem to be doing well enough	2011-01-17 22:39:54 +00:00
LoopUnswitch.cpp	Make LoopUnswitch preserve ScalarEvolution by just forgetting everything about	2011-02-11 06:08:28 +00:00
LowerAtomic.cpp
Makefile
MemCpyOptimizer.cpp	Spelling fix: consequtive -> consecutive.	2011-02-15 09:23:02 +00:00
Reassociate.cpp	RecursivelyDeleteTriviallyDeadInstructions only needs a	2011-03-10 20:57:44 +00:00
Reg2Mem.cpp
Scalar.cpp	Delete the GEPSplitter experiment.	2011-02-28 19:47:47 +00:00
ScalarReplAggregates.cpp	Fix a comment.	2011-03-16 08:13:42 +00:00
SCCP.cpp	SCCP doesn't actually preserve the CFG. It will delete and insert terminator	2011-01-21 08:38:09 +00:00
SimplifyCFGPass.cpp
SimplifyLibCalls.cpp	Preserve line number information while simplifying libcalls.	2011-03-09 21:27:52 +00:00
Sink.cpp
TailDuplication.cpp
TailRecursionElimination.cpp	Unbreak the MSVC build.	2011-01-29 20:06:16 +00:00