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
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Analysis	Propagate SCEV no-wrap flags whenever possible.	2011-03-15 00:37:00 +00:00
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Assembler	Reapply: Add type output to llvm-dis annotations. Patch by Yuri!	2011-03-17 19:50:04 +00:00
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CodeGen	SimplifyCFG has stopped duplicating returns into predecessors to canonicalize IR	2011-03-19 17:17:39 +00:00
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FrontendC	Disable test to unbreak Linux. Radar 9156771.	2011-03-19 03:56:38 +00:00
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MC	Fixed an assert by the ARM disassembler for LDRD_PRE/POST.	2011-03-19 01:16:20 +00:00
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Transforms	Avoid creating canonical induction variables for non-native types.	2011-03-18 16:50:32 +00:00
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