Chris Lattner f2dbf50efa turn things like: ... if (X == 0 || X == 2) ...where the comparisons and branches are in different blocks... into a switch instruction. This comes up a lot in various programs, and works well with the switch/switch merging code I checked earlier. For example, this testcase: int switchtest(int C) { return C == 0 ? f(123) : C == 1 ? f(3123) : C == 4 ? f(312) : C == 5 ? f(1234): f(444); } is converted into this: switch int %C, label %cond_false.3 [ int 0, label %cond_true.0 int 1, label %cond_true.1 int 4, label %cond_true.2 int 5, label %cond_true.3 ] instead of a whole bunch of conditional branches. Admittedly the code is ugly, and incomplete. To be complete, we need to add br -> switch merging and switch -> br merging. For example, this testcase: struct foo { int Q, R, Z; }; #define A (X->Q+X->R * 123) int test(struct foo *X) { return A == 123 ? X1() : A == 12321 ? X2(): (A == 111 || A == 222) ? X3() : A == 875 ? X4() : X5(); } Gets compiled to this: switch int %tmp.7, label %cond_false.2 [ int 123, label %cond_true.0 int 12321, label %cond_true.1 int 111, label %cond_true.2 int 222, label %cond_true.2 ] ... cond_false.2: ; preds = %entry %tmp.52 = seteq int %tmp.7, 875 ; <bool> [#uses=1] br bool %tmp.52, label %cond_true.3, label %cond_false.3 where the branch could be folded into the switch. This kind of thing occurs *ALL OF THE TIME*, especially in programs like 176.gcc, which is a horrible mess of code. It contains stuff like *shudder*: #define SWITCH_TAKES_ARG(CHAR) \ ( (CHAR) == 'D' \ || (CHAR) == 'U' \ || (CHAR) == 'o' \ || (CHAR) == 'e' \ || (CHAR) == 'u' \ || (CHAR) == 'I' \ || (CHAR) == 'm' \ || (CHAR) == 'L' \ || (CHAR) == 'A' \ || (CHAR) == 'h' \ || (CHAR) == 'z') and #define CONST_OK_FOR_LETTER_P(VALUE, C) \ ((C) == 'I' ? SMALL_INTVAL (VALUE) \ : (C) == 'J' ? SMALL_INTVAL (-(VALUE)) \ : (C) == 'K' ? (unsigned)(VALUE) < 32 \ : (C) == 'L' ? ((VALUE) & 0xffff) == 0 \ : (C) == 'M' ? integer_ok_for_set (VALUE) \ : (C) == 'N' ? (VALUE) < 0 \ : (C) == 'O' ? (VALUE) == 0 \ : (C) == 'P' ? (VALUE) >= 0 \ : 0) and #define LEGITIMIZE_ADDRESS(X,OLDX,MODE,WIN) \ { \ if (GET_CODE (X) == PLUS && CONSTANT_ADDRESS_P (XEXP (X, 1))) \ (X) = gen_rtx (PLUS, SImode, XEXP (X, 0), \ copy_to_mode_reg (SImode, XEXP (X, 1))); \ if (GET_CODE (X) == PLUS && CONSTANT_ADDRESS_P (XEXP (X, 0))) \ (X) = gen_rtx (PLUS, SImode, XEXP (X, 1), \ copy_to_mode_reg (SImode, XEXP (X, 0))); \ if (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 0)) == MULT) \ (X) = gen_rtx (PLUS, SImode, XEXP (X, 1), \ force_operand (XEXP (X, 0), 0)); \ if (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 1)) == MULT) \ (X) = gen_rtx (PLUS, SImode, XEXP (X, 0), \ force_operand (XEXP (X, 1), 0)); \ if (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 0)) == PLUS) \ (X) = gen_rtx (PLUS, Pmode, force_operand (XEXP (X, 0), NULL_RTX),\ XEXP (X, 1)); \ if (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 1)) == PLUS) \ (X) = gen_rtx (PLUS, Pmode, XEXP (X, 0), \ force_operand (XEXP (X, 1), NULL_RTX)); \ if (GET_CODE (X) == SYMBOL_REF || GET_CODE (X) == CONST \ || GET_CODE (X) == LABEL_REF) \ (X) = legitimize_address (flag_pic, X, 0, 0); \ if (memory_address_p (MODE, X)) \ goto WIN; } and others. These macros get used multiple times of course. These are such lovely candidates for macros, aren't they? :) This code also nicely handles LLVM constructs that look like this: if (isa<CastInst>(I)) ... else if (isa<BranchInst>(I)) ... else if (isa<SetCondInst>(I)) ... else if (isa<UnwindInst>(I)) ... else if (isa<VAArgInst>(I)) ... where the isa can obviously be a dyn_cast as well. Switch instructions are a good thing. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11870 91177308-0d34-0410-b5e6-96231b3b80d8		2004-02-26 07:13:46 +00:00
..
BasicBlockUtils.cpp	Finegrainify namespacification	2004-01-09 06:12:26 +00:00
BreakCriticalEdges.cpp	Finegrainify namespacification	2004-01-09 06:12:26 +00:00
CloneFunction.cpp	Minor speedup, don't query ValueMap each time through the loop	2004-02-04 21:44:26 +00:00
CloneModule.cpp	Finegrainify namespacification	2004-01-09 06:12:26 +00:00
CloneTrace.cpp	Give CloneBasicBlock an optional function argument to specify which function	2004-02-04 01:19:43 +00:00
DemoteRegToStack.cpp	Finegrainify namespacification	2004-01-09 06:12:26 +00:00
InlineFunction.cpp	Fix compilation of 126.gcc: intrinsic functions cannot throw, so they are not	2004-02-13 16:47:35 +00:00
Linker.cpp	Fix PR245: Linking weak and strong global variables is dependent on link order	2004-02-17 21:56:04 +00:00
Local.cpp	Clean up #includes	2004-01-12 19:56:36 +00:00
LoopSimplify.cpp	Fix another dominator update bug. These bugs keep getting exposed because GCSE	2004-02-05 23:20:59 +00:00
LowerAllocations.cpp	Hyphenate `target-dependent'	2004-01-28 20:43:01 +00:00
LowerInvoke.cpp	Instead of producing calls to setjmp/longjmp, produce uses of the	2004-02-15 22:24:27 +00:00
LowerSwitch.cpp	Fix incorrect debug code	2004-02-25 15:15:04 +00:00
Makefile	Added LLVM copyright notice to Makefiles.	2003-10-20 22:26:57 +00:00
Mem2Reg.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
PromoteMemoryToRegister.cpp	Bunch up all locally used allocas by the block they are allocated in, and	2004-02-03 22:34:12 +00:00
SimplifyCFG.cpp	turn things like:	2004-02-26 07:13:46 +00:00
UnifyFunctionExitNodes.cpp	Minor cleanups and simplifications	2003-11-21 16:52:05 +00:00
ValueMapper.cpp	Adjustments to support the new ConstantAggregateZero class	2004-02-15 05:55:15 +00:00
ValueMapper.h	Finegrainify namespacification	2004-01-09 06:12:26 +00:00