xcore backend: add pattern for CP offset memory fetch

[Robert Lytton]

Hi,

The XCore backend is fetching constants from the constant pool via an intermediate general register for the address.
The 'CP' register plus immediate offset should be targeted instead - saving an instruction and temporary register.

The patch below adds the missing "CP offset memory fetch" pattern to the target td.

robert


--- llvm/lib/Target/XCore/XCoreInstrInfo.td
+++ llvm/lib/Target/XCore/XCoreInstrInfo.td
@@ -283,7 +283,8 @@ multiclass FRU6_LRU6_cp<bits<6> opc, string OpcStr> {
   def _ru6: _FRU6<opc, (outs RRegs:$a), (ins i32imm:$b),
                   !strconcat(OpcStr, " $a, cp[$b]"), []>;
   def _lru6: _FLRU6<opc, (outs RRegs:$a), (ins i32imm:$b),
-                    !strconcat(OpcStr, " $a, cp[$b]"), []>;
+                    !strconcat(OpcStr, " $a, cp[$b]"),
+                    [(set RRegs:$a, (load (cprelwrapper tglobaladdr:$b)))]>;
 }

 // U6


--- llvm/test/CodeGen/XCore/constants.ll
+++ llvm/test/CodeGen/XCore/constants.ll
@@ -9,3 +9,16 @@ define i32 @f() {
 entry:
        ret i32 12345678
 }
+
+; CHECK: g:
+; CHECK: ldw [[REG:r[0-9]+]], cp[GConst]
+; CHECK: stw [[REG]], dp[GData]
+%struct = type <{ i32, i32 }>
+ at GConst = external constant %struct
+ at GData = external global %struct
+define void @g() nounwind {
+entry:
+  %0 = load i32* getelementptr (%struct* @GConst, i32 0, i32 0)
+  store i32 %0,  i32* getelementptr (%struct* @GData, i32 0, i32 0)
+  ret void
+}