[llvm-commits] CVS: llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp README.txt

[Chris Lattner]

Changes in directory llvm/lib/Target/PowerPC:

PPCISelDAGToDAG.cpp updated: 1.208 -> 1.209
README.txt updated: 1.96 -> 1.97
---
Log message:

Two improvements:

1. Codegen this comparison:
     if (X == 0x8000) 

as:

        cmplwi cr0, r3, 32768
        bne cr0, LBB1_2 ;cond_next

instead of:

        lis r2, 0
        ori r2, r2, 32768
        cmpw cr0, r3, r2
        bne cr0, LBB1_2 ;cond_next


2. Codegen this comparison:
      if (X == 0x12345678)

as:

        xoris r2, r3, 4660
        cmplwi cr0, r2, 22136
        bne cr0, LBB1_2 ;cond_next

instead of:

        lis r2, 4660
        ori r2, r2, 22136
        cmpw cr0, r3, r2
        bne cr0, LBB1_2 ;cond_next




---
Diffs of the changes:  (+27 -22)

 PPCISelDAGToDAG.cpp |   28 +++++++++++++++++++++++++++-
 README.txt          |   21 ---------------------
 2 files changed, 27 insertions(+), 22 deletions(-)


Index: llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
diff -u llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:1.208 llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:1.209
--- llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:1.208	Sun Aug 27 07:54:01 2006
+++ llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp	Tue Sep 19 23:25:47 2006
@@ -699,7 +699,33 @@
   
   if (LHS.getValueType() == MVT::i32) {
     unsigned Imm;
-    if (ISD::isUnsignedIntSetCC(CC)) {
+    if (CC == ISD::SETEQ || CC == ISD::SETNE) {
+      if (isInt32Immediate(RHS, Imm)) {
+        // SETEQ/SETNE comparison with 16-bit immediate, fold it.
+        if (isUInt16(Imm))
+          return SDOperand(CurDAG->getTargetNode(PPC::CMPLWI, MVT::i32, LHS,
+                                                 getI32Imm(Imm & 0xFFFF)), 0);
+        // If this is a 16-bit signed immediate, fold it.
+        if (isInt16(Imm))
+          return SDOperand(CurDAG->getTargetNode(PPC::CMPWI, MVT::i32, LHS,
+                                                 getI32Imm(Imm & 0xFFFF)), 0);
+        
+        // For non-equality comparisons, the default code would materialize the
+        // constant, then compare against it, like this:
+        //   lis r2, 4660
+        //   ori r2, r2, 22136 
+        //   cmpw cr0, r3, r2
+        // Since we are just comparing for equality, we can emit this instead:
+        //   xoris r0,r3,0x1234
+        //   cmplwi cr0,r0,0x5678
+        //   beq cr0,L6
+        SDOperand Xor(CurDAG->getTargetNode(PPC::XORIS, MVT::i32, LHS,
+                                            getI32Imm(Imm >> 16)), 0);
+        return SDOperand(CurDAG->getTargetNode(PPC::CMPLWI, MVT::i32, Xor,
+                                               getI32Imm(Imm & 0xFFFF)), 0);
+      }
+      Opc = PPC::CMPLW;
+    } else if (ISD::isUnsignedIntSetCC(CC)) {
       if (isInt32Immediate(RHS, Imm) && isUInt16(Imm))
         return SDOperand(CurDAG->getTargetNode(PPC::CMPLWI, MVT::i32, LHS,
                                                getI32Imm(Imm & 0xFFFF)), 0);


Index: llvm/lib/Target/PowerPC/README.txt
diff -u llvm/lib/Target/PowerPC/README.txt:1.96 llvm/lib/Target/PowerPC/README.txt:1.97
--- llvm/lib/Target/PowerPC/README.txt:1.96	Tue Sep 19 22:59:25 2006
+++ llvm/lib/Target/PowerPC/README.txt	Tue Sep 19 23:25:47 2006
@@ -50,27 +50,6 @@
 
 ===-------------------------------------------------------------------------===
 
-* Codegen this:
-
-   void test2(int X) {
-     if (X == 0x12345678) bar();
-   }
-
-    as:
-
-       xoris r0,r3,0x1234
-       cmplwi cr0,r0,0x5678
-       beq cr0,L6
-
-    not:
-
-        lis r2, 4660
-        ori r2, r2, 22136 
-        cmpw cr0, r3, r2  
-        bne .LBB_test2_2
-
-===-------------------------------------------------------------------------===
-
 Lump the constant pool for each function into ONE pic object, and reference
 pieces of it as offsets from the start.  For functions like this (contrived
 to have lots of constants obviously):