Teach basicaa that x|c == x+c when the c bits of x are clear. This

allows us to compile the example in readme.txt into:

LBB1_1:                                                     ## %bb
	movl	4(%rdx,%rax), %ecx
	movl	%ecx, %esi
	imull	(%rdx,%rax), %esi
	imull	%esi, %ecx
	movl	%esi, 8(%rdx,%rax)
	imull	%ecx, %esi
	movl	%ecx, 12(%rdx,%rax)
	movl	%esi, 16(%rdx,%rax)
	imull	%ecx, %esi
	movl	%esi, 20(%rdx,%rax)
	addq	$16, %rax
	cmpq	$4000, %rax
	jne	LBB1_1

instead of:

LBB1_1: 
	movl	(%rdx,%rax), %ecx
	imull	4(%rdx,%rax), %ecx
	movl	%ecx, 8(%rdx,%rax)
	imull	4(%rdx,%rax), %ecx
	movl	%ecx, 12(%rdx,%rax)
	imull	8(%rdx,%rax), %ecx
	movl	%ecx, 16(%rdx,%rax)
	imull	12(%rdx,%rax), %ecx
	movl	%ecx, 20(%rdx,%rax)
	addq	$16, %rax
	cmpq	$4000, %rax
	jne	LBB1_1

GCC (4.2) doesn't seem to be able to eliminate the loads in this 
testcase either, it generates:

L2:
	movl	(%rdx), %eax
	imull	4(%rdx), %eax
	movl	%eax, 8(%rdx)
	imull	4(%rdx), %eax
	movl	%eax, 12(%rdx)
	imull	8(%rdx), %eax
	movl	%eax, 16(%rdx)
	imull	12(%rdx), %eax
	movl	%eax, 20(%rdx)
	addl	$4, %ecx
	addq	$16, %rdx
	cmpl	$1002, %ecx
	jne	L2




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89952 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 17 deletions

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 3096f95ede..2db580824c 100644
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -443,23 +443,6 @@ entry:
 
 //===---------------------------------------------------------------------===//
 
-"basicaa" should know how to look through "or" instructions that act like add
-instructions.  For example in this code, the x*4+1 is turned into x*4 | 1, and
-basicaa can't analyze the array subscript, leading to duplicated loads in the
-generated code:
-
-void test(int X, int Y, int a[]) {
-int i;
-  for (i=2; i<1000; i+=4) {
-  a[i+0] = a[i-1+0]*a[i-2+0];
-  a[i+1] = a[i-1+1]*a[i-2+1];
-  a[i+2] = a[i-1+2]*a[i-2+2];
-  a[i+3] = a[i-1+3]*a[i-2+3];
-  }
-}
-
-//===---------------------------------------------------------------------===//
-
 We should investigate an instruction sinking pass.  Consider this silly
 example in pic mode: