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

4 files changed, 76 insertions, 5 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)>;
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index 41d4e206491..cf1fbfa1abb 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -96,14 +96,19 @@ def t2_so_imm_neg : Operand<i32>, PatLeaf<(imm), [{
 }
 
 /// imm0_4095 predicate - True if the 32-bit immediate is in the range [0.4095].
-def imm0_4095 : Operand<i32>,
-                ImmLeaf<i32, [{
+def imm0_4095_asmoperand: ImmAsmOperand { let Name = "Imm0_4095"; }
+def imm0_4095 : Operand<i32>, ImmLeaf<i32, [{
   return Imm >= 0 && Imm < 4096;
-}]>;
+}]> {
+  let ParserMatchClass = imm0_4095_asmoperand;
+}
 
-def imm0_4095_neg : PatLeaf<(i32 imm), [{
+def imm0_4095_neg_asmoperand: AsmOperandClass { let Name = "Imm0_4095Neg"; }
+def imm0_4095_neg : Operand<i32>, PatLeaf<(i32 imm), [{
  return (uint32_t)(-N->getZExtValue()) < 4096;
-}], imm_neg_XFORM>;
+}], imm_neg_XFORM> {
+  let ParserMatchClass = imm0_4095_neg_asmoperand;
+}
 
 def imm0_255_neg : PatLeaf<(i32 imm), [{
   return (uint32_t)(-N->getZExtValue()) < 255;
@@ -3969,6 +3974,19 @@ def : t2InstAlias<"add${s}${p} $Rdn, $ShiftedRm",
                   (t2ADDrs GPRnopc:$Rdn, GPRnopc:$Rdn, t2_so_reg:$ShiftedRm,
                            pred:$p, cc_out:$s)>;
 
+// add w/ negative immediates is just a sub.
+def : t2InstAlias<"add${s}${p} $Rd, $Rn, $imm",
+        (t2SUBri GPRnopc:$Rd, GPRnopc:$Rn, t2_so_imm_neg:$imm, pred:$p,
+                 cc_out:$s)>;
+def : t2InstAlias<"add${p} $Rd, $Rn, $imm",
+           (t2SUBri12 GPRnopc:$Rd, GPR:$Rn, imm0_4095_neg:$imm, pred:$p)>;
+def : t2InstAlias<"add${s}${p} $Rdn, $imm",
+      (t2SUBri GPRnopc:$Rdn, GPRnopc:$Rdn, t2_so_imm_neg:$imm, pred:$p,
+               cc_out:$s)>;
+def : t2InstAlias<"add${p} $Rdn, $imm",
+           (t2SUBri12 GPRnopc:$Rdn, GPRnopc:$Rdn, imm0_4095_neg:$imm, pred:$p)>;
+
+
 // Aliases for SUB without the ".w" optional width specifier.
 def : t2InstAlias<"sub${s}${p} $Rd, $Rn, $imm",
         (t2SUBri GPRnopc:$Rd, GPRnopc:$Rn, t2_so_imm:$imm, pred:$p, cc_out:$s)>;
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index a558a61592f..e9164bcfa81 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -579,6 +579,14 @@ public:
     int64_t Value = CE->getValue();
     return ((Value & 3) == 0) && Value >= 0 && Value <= 508;
   }
+  bool isImm0_508s4Neg() const {
+    if (!isImm()) return false;
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+    if (!CE) return false;
+    int64_t Value = -CE->getValue();
+    // explicitly exclude zero. we want that to use the normal 0_508 version.
+    return ((Value & 3) == 0) && Value > 0 && Value <= 508;
+  }
   bool isImm0_255() const {
     if (!isImm()) return false;
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
@@ -586,6 +594,20 @@ public:
     int64_t Value = CE->getValue();
     return Value >= 0 && Value < 256;
   }
+  bool isImm0_4095() const {
+    if (!isImm()) return false;
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+    if (!CE) return false;
+    int64_t Value = CE->getValue();
+    return Value >= 0 && Value < 4096;
+  }
+  bool isImm0_4095Neg() const {
+    if (!isImm()) return false;
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+    if (!CE) return false;
+    int64_t Value = -CE->getValue();
+    return Value > 0 && Value < 4096;
+  }
   bool isImm0_1() const {
     if (!isImm()) return false;
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
@@ -1499,6 +1521,14 @@ public:
     Inst.addOperand(MCOperand::CreateImm(CE->getValue() / 4));
   }
 
+  void addImm0_508s4NegOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 1 && "Invalid number of operands!");
+    // The immediate is scaled by four in the encoding and is stored
+    // in the MCInst as such. Lop off the low two bits here.
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+    Inst.addOperand(MCOperand::CreateImm(-(CE->getValue() / 4)));
+  }
+
   void addImm0_508s4Operands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     // The immediate is scaled by four in the encoding and is stored
@@ -1557,6 +1587,14 @@ public:
     Inst.addOperand(MCOperand::CreateImm(-CE->getValue()));
   }
 
+  void addImm0_4095NegOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 1 && "Invalid number of operands!");
+    // The operand is actually an imm0_4095, but we have its
+    // negation in the assembly source, so twiddle it here.
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+    Inst.addOperand(MCOperand::CreateImm(-CE->getValue()));
+  }
+
   void addARMSOImmNotOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     // The operand is actually a so_imm, but we have its bitwise
diff --git a/llvm/test/MC/ARM/basic-thumb-instructions.s b/llvm/test/MC/ARM/basic-thumb-instructions.s
index 6e830cd557f..0a083d07228 100644
--- a/llvm/test/MC/ARM/basic-thumb-instructions.s
+++ b/llvm/test/MC/ARM/basic-thumb-instructions.s
@@ -59,12 +59,16 @@ _func:
         add sp, sp, #4
         add r2, sp, #8
         add r2, sp, #1020
+	add sp, sp, #-8
+	add sp, #-8
 
 @ CHECK: add	sp, #4                  @ encoding: [0x01,0xb0]
 @ CHECK: add	sp, #508                @ encoding: [0x7f,0xb0]
 @ CHECK: add	sp, #4                  @ encoding: [0x01,0xb0]
 @ CHECK: add	r2, sp, #8              @ encoding: [0x02,0xaa]
 @ CHECK: add	r2, sp, #1020           @ encoding: [0xff,0xaa]
+@ CHECK: sub	sp, #8                  @ encoding: [0x82,0xb0]
+@ CHECK: sub	sp, #8                  @ encoding: [0x82,0xb0]
 
 
 @------------------------------------------------------------------------------