Remove incorrect substitution pattern for UXTB16. It wrongly assumed the input shift was actually a rotate. rdar://8240138
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109693 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMInstrThumb2.td b/lib/Target/ARM/ARMInstrThumb2.td
index 8ba2376..c950fcb 100644
--- a/lib/Target/ARM/ARMInstrThumb2.td
+++ b/lib/Target/ARM/ARMInstrThumb2.td
@@ -1352,8 +1352,12 @@
defm t2UXTB16 : T2I_unary_rrot_uxtb16<0b011, "uxtb16",
UnOpFrag<(and node:$Src, 0x00FF00FF)>>;
-def : T2Pat<(and (shl GPR:$Src, (i32 8)), 0xFF00FF),
- (t2UXTB16r_rot GPR:$Src, 24)>, Requires<[HasT2ExtractPack]>;
+// FIXME: This pattern incorrectly assumes the shl operator is a rotate.
+// The transformation should probably be done as a combiner action
+// instead so we can include a check for masking back in the upper
+// eight bits of the source into the lower eight bits of the result.
+//def : T2Pat<(and (shl GPR:$Src, (i32 8)), 0xFF00FF),
+// (t2UXTB16r_rot GPR:$Src, 24)>, Requires<[HasT2ExtractPack]>;
def : T2Pat<(and (srl GPR:$Src, (i32 8)), 0xFF00FF),
(t2UXTB16r_rot GPR:$Src, 8)>, Requires<[HasT2ExtractPack]>;