[llvm-commits] [llvm] r109448 - /llvm/trunk/lib/Target/ARM/README.txt

[Anton Korobeynikov]

Author: asl
Date: Mon Jul 26 16:48:35 2010
New Revision: 109448

URL: http://llvm.org/viewvc/llvm-project?rev=109448&view=rev
Log:
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Modified:
    llvm/trunk/lib/Target/ARM/README.txt

Modified: llvm/trunk/lib/Target/ARM/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/README.txt?rev=109448&r1=109447&r2=109448&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/README.txt (original)
+++ llvm/trunk/lib/Target/ARM/README.txt Mon Jul 26 16:48:35 2010
@@ -636,3 +636,24 @@
 version.
 
 //===---------------------------------------------------------------------===//
+
+Consider the following simple C code:
+
+void foo(unsigned char *a, unsigned char *b, int *c) {
+ if ((*a | *b) == 0) *c = 0;
+}
+
+currently llvm-gcc generates something like this (nice branchless code I'd say):
+
+       ldrb    r0, [r0]
+       ldrb    r1, [r1]
+       orr     r0, r1, r0
+       tst     r0, #255
+       moveq   r0, #0
+       streq   r0, [r2]
+       bx      lr
+
+Note that both "tst" and "moveq" are redundant.
+
+//===---------------------------------------------------------------------===//
+