File backport-llvm-r197802 of Package llvm.7809

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File backport-llvm-r197802 of Package llvm.7809

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r197802 | rsandifo | 2013-12-20 12:49:48 +0100 (Fri, 20 Dec 2013) | 11 lines

[SystemZ] Extend RISBG optimization

The handling of ANY_EXTEND and ZERO_EXTEND was too strict.  In this context
we can treat ZERO_EXTEND in much the same way as an AND and then also handle
outermost ZERO_EXTENDs.

I couldn't find a test that benefited from the ANY_EXTEND change, but it's
more obvious to write it this way once SIGN_EXTEND and ZERO_EXTEND are
handled differently.

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Index: test/CodeGen/SystemZ/risbg-01.ll
===================================================================
--- test/CodeGen/SystemZ/risbg-01.ll.orig
+++ test/CodeGen/SystemZ/risbg-01.ll
@@ -457,11 +457,22 @@ define i64 @f40(i64 %foo, i64 *%dest) {
   ret i64 %and
 }
 
+; Check a case where the result is zero-extended.
+define i64 @f41(i32 %a) {
+; CHECK-LABEL: f41
+; CHECK: risbg %r2, %r2, 36, 191, 62
+; CHECK: br %r14
+  %shl = shl i32 %a, 2
+  %shr = lshr i32 %shl, 4
+  %ext = zext i32 %shr to i64
+  ret i64 %ext
+}
+
 ; In this case the sign extension is converted to a pair of 32-bit shifts,
 ; which is then extended to 64 bits.  We previously used the wrong bit size
 ; when testing whether the shifted-in bits of the shift right were significant.
-define i64 @f41(i1 %x) {
-; CHECK-LABEL: f41:
+define i64 @f42(i1 %x) {
+; CHECK-LABEL: f42:
 ; CHECK: sll %r2, 31
 ; CHECK: sra %r2, 31
 ; CHECK: llgcr %r2, %r2
Index: lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
===================================================================
--- lib/Target/SystemZ/SystemZISelDAGToDAG.cpp.orig
+++ lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
@@ -764,9 +764,22 @@ bool SystemZDAGToDAGISel::expandRxSBG(Rx
     return true;
   }
       
-  case ISD::SIGN_EXTEND:
-  case ISD::ZERO_EXTEND:
-  case ISD::ANY_EXTEND: {
+  case ISD::ANY_EXTEND:
+    // Bits above the extended operand are don't-care.
+    RxSBG.Input = N.getOperand(0);
+    return true;
+
+  case ISD::ZERO_EXTEND: {
+    // Restrict the mask to the extended operand.
+    unsigned InnerBitSize = N.getOperand(0).getValueType().getSizeInBits();
+    if (!refineRxSBGMask(RxSBG, allOnes(InnerBitSize)))
+      return false;
+
+    RxSBG.Input = N.getOperand(0);
+    return true;
+  }
+
+  case ISD::SIGN_EXTEND: {
     // Check that the extension bits are don't-care (i.e. are masked out
     // by the final mask).
     unsigned InnerBitSize = N.getOperand(0).getValueType().getSizeInBits();
@@ -1064,6 +1077,7 @@ SDNode *SystemZDAGToDAGISel::Select(SDNo
   case ISD::ROTL:
   case ISD::SHL:
   case ISD::SRL:
+  case ISD::ZERO_EXTEND:
     if (!ResNode)
       ResNode = tryRISBGZero(Node);
     break;

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