Evan Cheng c5f50f7322 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 llvm-svn: 127953		2011-03-19 17:17:39 +00:00
..
Alpha
ARM	Match a few more obvious patterns to revsh. rdar://9147637.	2011-03-18 21:52:42 +00:00
Blackfin	Be nice to Xcore and the XMOS assembler and avoid quoting section names	2011-03-04 20:03:14 +00:00
CBackend
CellSPU	Roll r127459 back in:	2011-03-11 21:52:04 +00:00
CPP
Generic	Make this test x86 specific because the ARM backend can't handle it.	2011-02-28 12:30:47 +00:00
MBlaze
Mips	Revert "Re-enable test and hope to silence the buildbots", still broken.	2011-03-09 22:48:46 +00:00
MSP430
PowerPC	Fix mistyped CHECK lines.	2011-03-09 22:07:31 +00:00
PTX	PTX: Fix various codegen issues	2011-03-18 19:24:28 +00:00
SPARC
SystemZ
Thumb	Roll r127459 back in:	2011-03-11 21:52:04 +00:00
Thumb2	Roll r127459 back in:	2011-03-11 21:52:04 +00:00
X86	SimplifyCFG has stopped duplicating returns into predecessors to canonicalize IR	2011-03-19 17:17:39 +00:00
XCore	Add XCore intrinsic for setpsc.	2011-03-17 18:42:05 +00:00