(sub X, imm) gets canonicalized to (add X, -imm)

There are patterns to handle immediates when they fit in the immediate field.
e.g. %sub = add i32 %x, -123
=>   sub r0, r0, #123
Add patterns to catch immediates that do not fit but should be materialized
with a single movw instruction rather than movw + movt pair.
e.g. %sub = add i32 %x, -65535
=>   movw r1, #65535
     sub r0, r0, r1

rdar://11726136


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159057 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMInstrInfo.td

@@ -253,9 +253,9 @@ class RegConstraint<string C> {
 //  ARM specific transformation functions and pattern fragments.
 //
 
-// so_imm_neg_XFORM - Return a so_imm value packed into the format described for
-// so_imm_neg def below.
-def so_imm_neg_XFORM : SDNodeXForm<imm, [{
+// imm_neg_XFORM - Return a imm value packed into the format described for
+// imm_neg defs below.
+def imm_neg_XFORM : SDNodeXForm<imm, [{
   return CurDAG->getTargetConstant(-(int)N->getZExtValue(), MVT::i32);
 }]>;
 
@@ -274,7 +274,7 @@ def so_imm_neg_asmoperand : AsmOperandClass { let Name = "ARMSOImmNeg"; }
 def so_imm_neg : Operand<i32>, PatLeaf<(imm), [{
     int64_t Value = -(int)N->getZExtValue();
     return Value && ARM_AM::getSOImmVal(Value) != -1;
-  }], so_imm_neg_XFORM> {
+  }], imm_neg_XFORM> {
   let ParserMatchClass = so_imm_neg_asmoperand;
 }
 
@@ -635,6 +635,11 @@ def imm0_65535 : Operand<i32>, ImmLeaf<i32, [{
   let ParserMatchClass = Imm0_65535AsmOperand;
 }
 
+// imm0_65535_neg - An immediate whose negative value is in the range [0.65535].
+def imm0_65535_neg : Operand<i32>, ImmLeaf<i32, [{
+  return -Imm >= 0 && -Imm < 65536;
+}]>;
+
 // imm0_65535_expr - For movt/movw - 16-bit immediate that can also reference
 // a relocatable expression.
 //
@@ -3077,6 +3082,11 @@ def : ARMPat<(add     GPR:$src, so_imm_neg:$imm),
 def : ARMPat<(ARMaddc GPR:$src, so_imm_neg:$imm),
              (SUBSri  GPR:$src, so_imm_neg:$imm)>;
 
+def : ARMPat<(add     GPR:$src, imm0_65535_neg:$imm),
+             (SUBrr   GPR:$src, (MOVi16 (imm_neg_XFORM imm:$imm)))>;
+def : ARMPat<(ARMaddc GPR:$src, imm0_65535_neg:$imm),
+             (SUBSrr  GPR:$src, (MOVi16 (imm_neg_XFORM imm:$imm)))>;
+
 // The with-carry-in form matches bitwise not instead of the negation.
 // Effectively, the inverse interpretation of the carry flag already accounts
 // for part of the negation.

lib/Target/ARM/ARMInstrThumb.td

@@ -32,9 +32,6 @@ def imm_sr : Operand<i32>, PatLeaf<(imm), [{
   let ParserMatchClass = ThumbSRImmAsmOperand;
 }
 
-def imm_neg_XFORM : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(-(int)N->getZExtValue(), MVT::i32);
-}]>;
 def imm_comp_XFORM : SDNodeXForm<imm, [{
   return CurDAG->getTargetConstant(~((uint32_t)N->getZExtValue()), MVT::i32);
 }]>;

lib/Target/ARM/ARMInstrThumb2.td

@@ -1931,11 +1931,16 @@ def : T2Pat<(add        GPR:$src, t2_so_imm_neg:$imm),
             (t2SUBri    GPR:$src, t2_so_imm_neg:$imm)>;
 def : T2Pat<(add        GPR:$src, imm0_4095_neg:$imm),
             (t2SUBri12  GPR:$src, imm0_4095_neg:$imm)>;
+def : T2Pat<(add        GPR:$src, imm0_65535_neg:$imm),
+            (t2SUBrr    GPR:$src, (t2MOVi16 (imm_neg_XFORM imm:$imm)))>;
+
 let AddedComplexity = 1 in
 def : T2Pat<(ARMaddc    rGPR:$src, imm0_255_neg:$imm),
             (t2SUBSri   rGPR:$src, imm0_255_neg:$imm)>;
 def : T2Pat<(ARMaddc    rGPR:$src, t2_so_imm_neg:$imm),
             (t2SUBSri   rGPR:$src, t2_so_imm_neg:$imm)>;
+def : T2Pat<(ARMaddc    rGPR:$src, imm0_65535_neg:$imm),
+            (t2SUBSrr   rGPR:$src, (t2MOVi16 (imm_neg_XFORM imm:$imm)))>;
 // The with-carry-in form matches bitwise not instead of the negation.
 // Effectively, the inverse interpretation of the carry flag already accounts
 // for part of the negation.
@@ -1944,6 +1949,8 @@ def : T2Pat<(ARMadde    rGPR:$src, imm0_255_not:$imm, CPSR),
             (t2SBCri    rGPR:$src, imm0_255_not:$imm)>;
 def : T2Pat<(ARMadde    rGPR:$src, t2_so_imm_not:$imm, CPSR),
             (t2SBCri    rGPR:$src, t2_so_imm_not:$imm)>;
+def : T2Pat<(ARMadde    rGPR:$src, imm0_65535_neg:$imm, CPSR),
+            (t2SBCrr    rGPR:$src, (t2MOVi16 (imm_neg_XFORM imm:$imm)))>;
 
 // Select Bytes -- for disassembly only
 

test/CodeGen/ARM/sub.ll

@@ -36,3 +36,15 @@ entry:
   %sel = select i1 %cmp, i32 1, i32 %sub
   ret i32 %sel
 }
+
+; rdar://11726136
+define i32 @f5(i32 %x) {
+entry:
+; CHECK: f5
+; CHECK: movw r1, #65535
+; CHECK-NOT: movt
+; CHECK-NOT: add
+; CHECK: sub r0, r0, r1
+  %sub = add i32 %x, -65535
+  ret i32 %sub
+}