[PATCH] D11132: [ARM] Handle commutativity when converting to tADDhirr in Thumb2

[scott douglass]

scott-0 created this revision.
scott-0 added a subscriber: llvm-commits.
Herald added subscribers: rengolin, aemerson.

http://reviews.llvm.org/D11132

Files:
  lib/Target/ARM/AsmParser/ARMAsmParser.cpp
  test/MC/ARM/thumb2-narrow-dp.ll

Index: test/MC/ARM/thumb2-narrow-dp.ll
===================================================================
--- test/MC/ARM/thumb2-narrow-dp.ll
+++ test/MC/ARM/thumb2-narrow-dp.ll
@@ -44,6 +44,8 @@
 // CHECK: adds  r0, r2, r1          @ encoding: [0x50,0x18]
     ADDS     r2, r2, r1          // ADDS has T1 narrow 3 operand
 // CHECK: adds  r2, r2, r1          @ encoding: [0x52,0x18]
+    ADD      r3, r1, r3          // T2
+// CHECK: add  r3, r1               @ encoding: [0x0b,0x44]
 
     IT EQ
 // CHECK: it eq                     @ encoding: [0x08,0xbf]
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -8215,17 +8215,25 @@
     // If the destination and first source operand are the same, and
     // there's no setting of the flags, use encoding T2 instead of T3.
     // Note that this is only for ADD, not SUB. This mirrors the system
-    // 'as' behaviour. Make sure the wide encoding wasn't explicit.
-    if (Inst.getOperand(0).getReg() != Inst.getOperand(1).getReg() ||
+    // 'as' behaviour.  Also take advantage of ADD being commutative.
+    // Make sure the wide encoding wasn't explicit.
+    bool Swap = false;
+    auto DestReg = Inst.getOperand(0).getReg();
+    bool Transform = DestReg == Inst.getOperand(1).getReg();
+    if (!Transform && DestReg == Inst.getOperand(2).getReg()) {
+      Transform = true;
+      Swap = true;
+    }
+    if (!Transform ||
         Inst.getOperand(5).getReg() != 0 ||
         (static_cast<ARMOperand &>(*Operands[3]).isToken() &&
          static_cast<ARMOperand &>(*Operands[3]).getToken() == ".w"))
       break;
     MCInst TmpInst;
     TmpInst.setOpcode(ARM::tADDhirr);
     TmpInst.addOperand(Inst.getOperand(0));
     TmpInst.addOperand(Inst.getOperand(0));
-    TmpInst.addOperand(Inst.getOperand(2));
+    TmpInst.addOperand(Inst.getOperand(Swap ? 1 : 2));
     TmpInst.addOperand(Inst.getOperand(3));
     TmpInst.addOperand(Inst.getOperand(4));
     Inst = TmpInst;


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