ARM assembly aliases for add negative immediates using sub.

'add r2, #-1024' should just use 'sub r2, #1024' rather than erroring out.
Thumb1 aliases for adding a negative immediate to the stack pointer,
also.

rdar://11192734

llvm-svn: 154123

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index ba1791b8f74..6c9a55cf647 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -91,6 +91,12 @@ def t_imm0_508s4 : Operand<i32> {
   let ParserMatchClass = t_imm0_508s4_asmoperand;
   let OperandType = "OPERAND_IMMEDIATE";
 }
+// Alias use only, so no printer is necessary.
+def t_imm0_508s4_neg_asmoperand: AsmOperandClass { let Name = "Imm0_508s4Neg"; }
+def t_imm0_508s4_neg : Operand<i32> {
+  let ParserMatchClass = t_imm0_508s4_neg_asmoperand;
+  let OperandType = "OPERAND_IMMEDIATE";
+}
 
 // Define Thumb specific addressing modes.
 
@@ -345,6 +351,11 @@ def tSUBspi : T1pIt<(outs GPRsp:$Rdn), (ins GPRsp:$Rn, t_imm0_508s4:$imm),
   let DecoderMethod = "DecodeThumbAddSPImm";
 }
 
+def : tInstAlias<"add${p} sp, $imm",
+                 (tSUBspi SP, t_imm0_508s4_neg:$imm, pred:$p)>;
+def : tInstAlias<"add${p} sp, sp, $imm",
+                 (tSUBspi SP, t_imm0_508s4_neg:$imm, pred:$p)>;
+
 // Can optionally specify SP as a three operand instruction.
 def : tInstAlias<"add${p} sp, sp, $imm",
                  (tADDspi SP, t_imm0_508s4:$imm, pred:$p)>;