[llvm-commits] [llvm] r159864 - /llvm/trunk/lib/Target/ARM/README.txt

[Jim Grosbach]

Author: grosbach
Date: Fri Jul  6 16:52:04 2012
New Revision: 159864

URL: http://llvm.org/viewvc/llvm-project?rev=159864&view=rev
Log:
ARM: Add test cleanup entry to the README.

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=159864&r1=159863&r2=159864&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/README.txt (original)
+++ llvm/trunk/lib/Target/ARM/README.txt Fri Jul  6 16:52:04 2012
@@ -710,3 +710,24 @@
 this in a target-independent way: we should probably fold that (when using
 "undefined at zero" semantics) to set the "defined at zero" bit and have
 the code generator expand out the right code.
+
+
+//===---------------------------------------------------------------------===//
+
+Clean up the test/MC/ARM files to have more robust register choices.
+
+R0 should not be used as a register operand in the assembler tests as it's then
+not possible to distinguish between a correct encoding and a missing operand
+encoding, as zero is the default value for the binary encoder.
+e.g.,
+    add r0, r0  // bad
+    add r3, r5  // good
+
+Register operands should be distinct. That is, when the encoding does not
+require two syntactical operands to refer to the same register, two different
+registers should be used in the test so as to catch errors where the
+operands are swapped in the encoding.
+e.g.,
+    subs.w r1, r1, r1 // bad
+    subs.w r1, r2, r3 // good
+