Chris Lattner 3d834bf2c3 Do not fold (X + C1 != C2) if there are other users of the add. Doing ... this transformation used to take a loop like this: int Array[1000]; void test(int X) { int i; for (i = 0; i < 1000; ++i) Array[i] += X; } Compiled to LLVM is: no_exit: ; preds = %entry, %no_exit %indvar = phi uint [ 0, %entry ], [ %indvar.next, %no_exit ] ; <uint> [#uses=2] %tmp.4 = getelementptr [1000 x int]* %Array, int 0, uint %indvar ; <int*> [#uses=2] %tmp.7 = load int* %tmp.4 ; <int> [#uses=1] %tmp.9 = add int %tmp.7, %X ; <int> [#uses=1] store int %tmp.9, int* %tmp.4 *** %indvar.next = add uint %indvar, 1 ; <uint> [#uses=2] *** %exitcond = seteq uint %indvar.next, 1000 ; <bool> [#uses=1] br bool %exitcond, label %return, label %no_exit and turn it into a loop like this: no_exit: ; preds = %entry, %no_exit %indvar = phi uint [ 0, %entry ], [ %indvar.next, %no_exit ] ; <uint> [#uses=3] %tmp.4 = getelementptr [1000 x int]* %Array, int 0, uint %indvar ; <int*> [#uses=2] %tmp.7 = load int* %tmp.4 ; <int> [#uses=1] %tmp.9 = add int %tmp.7, %X ; <int> [#uses=1] store int %tmp.9, int* %tmp.4 *** %indvar.next = add uint %indvar, 1 ; <uint> [#uses=1] *** %exitcond = seteq uint %indvar, 999 ; <bool> [#uses=1] br bool %exitcond, label %return, label %no_exit Note that indvar.next and indvar can no longer be coallesced. In machine code terms, this patch changes this code: .LBBtest_1: # no_exit mov %EDX, OFFSET Array mov %ESI, %EAX add %ESI, DWORD PTR [%EDX + 4*%ECX] mov %EDX, OFFSET Array mov DWORD PTR [%EDX + 4*%ECX], %ESI mov %EDX, %ECX inc %EDX cmp %ECX, 999 mov %ECX, %EDX jne .LBBtest_1 # no_exit into this: .LBBtest_1: # no_exit mov %EDX, OFFSET Array mov %ESI, %EAX add %ESI, DWORD PTR [%EDX + 4*%ECX] mov %EDX, OFFSET Array mov DWORD PTR [%EDX + 4*%ECX], %ESI inc %ECX cmp %ECX, 1000 jne .LBBtest_1 # no_exit We need better instruction selection to get this: .LBBtest_1: # no_exit add DWORD PTR [Array + 4*%ECX], EAX inc %ECX cmp %ECX, 1000 jne .LBBtest_1 # no_exit ... but at least there is less register juggling git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16473 91177308-0d34-0410-b5e6-96231b3b80d8		2004-09-21 21:35:23 +00:00
..
Hello	Add a newline	2004-09-15 17:53:52 +00:00
Instrumentation	'Pass' should now not be derived from by clients. Instead, they should derive	2004-09-20 04:48:05 +00:00
IPO	'Pass' should now not be derived from by clients. Instead, they should derive	2004-09-20 04:48:05 +00:00
Scalar	Do not fold (X + C1 != C2) if there are other users of the add. Doing	2004-09-21 21:35:23 +00:00
Utils	Prototype these functions more accurately	2004-09-20 04:43:15 +00:00
ExprTypeConvert.cpp	Changes For Bug 352	2004-09-01 22:55:40 +00:00
LevelRaise.cpp	Prototype more accurately	2004-09-20 04:43:57 +00:00
Makefile	Added LLVM copyright notice to Makefiles.	2003-10-20 22:26:57 +00:00
TransformInternals.cpp	Merge i*.h headers into Instructions.h as part of bug403.	2004-07-29 12:17:34 +00:00
TransformInternals.h	Put all LLVM code into the llvm namespace, as per bug 109.	2003-11-11 22:41:34 +00:00