File backport-llvm-r197238 of Package llvm

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File backport-llvm-r197238 of Package llvm

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r197238 | rsandifo | 2013-12-13 16:46:55 +0100 (Fri, 13 Dec 2013) | 8 lines

[SystemZ] Make more use of TMHH

This originally came about after noticing that InstCombine turns
some of the TMHH (icmp (and...), ...) tests into plain comparisons.
Since there is no instruction to compare with a 64-bit immediate,
TMHH is generally better than an ordered comparison for the cases
that it can handle.

------------------------------------------------------------------------
Index: lib/Target/SystemZ/SystemZISelLowering.cpp
===================================================================
--- lib/Target/SystemZ/SystemZISelLowering.cpp.orig
+++ lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1440,47 +1440,75 @@ static void adjustForTestUnderMask(Selec
   uint64_t CmpVal = ConstOp1->getZExtValue();
 
   // Check whether the nonconstant input is an AND with a constant mask.
-  if (C.Op0.getOpcode() != ISD::AND)
-    return;
-  SDValue AndOp0 = C.Op0.getOperand(0);
-  SDValue AndOp1 = C.Op0.getOperand(1);
-  ConstantSDNode *Mask = dyn_cast<ConstantSDNode>(AndOp1.getNode());
-  if (!Mask)
-    return;
-  uint64_t MaskVal = Mask->getZExtValue();
+  Comparison NewC(C);
+  uint64_t MaskVal;
+  ConstantSDNode *Mask = 0;
+  if (C.Op0.getOpcode() == ISD::AND) {
+    NewC.Op0 = C.Op0.getOperand(0);
+    NewC.Op1 = C.Op0.getOperand(1);
+    Mask = dyn_cast<ConstantSDNode>(NewC.Op1);
+    if (!Mask)
+      return;
+    MaskVal = Mask->getZExtValue();
+  } else {
+    // There is no instruction to compare with a 64-bit immediate
+    // so use TMHH instead if possible.  We need an unsigned ordered
+    // comparison with an i64 immediate.
+    if (NewC.Op0.getValueType() != MVT::i64 ||
+        NewC.CCMask == SystemZ::CCMASK_CMP_EQ ||
+        NewC.CCMask == SystemZ::CCMASK_CMP_NE ||
+        NewC.ICmpType == SystemZICMP::SignedOnly)
+      return;
+    // Convert LE and GT comparisons into LT and GE.
+    if (NewC.CCMask == SystemZ::CCMASK_CMP_LE ||
+        NewC.CCMask == SystemZ::CCMASK_CMP_GT) {
+      if (CmpVal == uint64_t(-1))
+        return;
+      CmpVal += 1;
+      NewC.CCMask ^= SystemZ::CCMASK_CMP_EQ;
+    }
+    // If the low N bits of Op1 are zero than the low N bits of Op0 can
+    // be masked off without changing the result.
+    MaskVal = -(CmpVal & -CmpVal);
+    NewC.ICmpType = SystemZICMP::UnsignedOnly;
+  }
 
   // Check whether the combination of mask, comparison value and comparison
   // type are suitable.
-  unsigned BitSize = C.Op0.getValueType().getSizeInBits();
+  unsigned BitSize = NewC.Op0.getValueType().getSizeInBits();
   unsigned NewCCMask, ShiftVal;
-  if (C.ICmpType != SystemZICMP::SignedOnly &&
-      AndOp0.getOpcode() == ISD::SHL &&
-      isSimpleShift(AndOp0, ShiftVal) &&
-      (NewCCMask = getTestUnderMaskCond(BitSize, C.CCMask, MaskVal >> ShiftVal,
+  if (NewC.ICmpType != SystemZICMP::SignedOnly &&
+      NewC.Op0.getOpcode() == ISD::SHL &&
+      isSimpleShift(NewC.Op0, ShiftVal) &&
+      (NewCCMask = getTestUnderMaskCond(BitSize, NewC.CCMask,
+                                        MaskVal >> ShiftVal,
                                         CmpVal >> ShiftVal,
                                         SystemZICMP::Any))) {
-    AndOp0 = AndOp0.getOperand(0);
-    AndOp1 = DAG.getConstant(MaskVal >> ShiftVal, AndOp0.getValueType());
-  } else if (C.ICmpType != SystemZICMP::SignedOnly &&
-             AndOp0.getOpcode() == ISD::SRL &&
-             isSimpleShift(AndOp0, ShiftVal) &&
-             (NewCCMask = getTestUnderMaskCond(BitSize, C.CCMask,
+    NewC.Op0 = NewC.Op0.getOperand(0);
+    MaskVal >>= ShiftVal;
+  } else if (NewC.ICmpType != SystemZICMP::SignedOnly &&
+             NewC.Op0.getOpcode() == ISD::SRL &&
+             isSimpleShift(NewC.Op0, ShiftVal) &&
+             (NewCCMask = getTestUnderMaskCond(BitSize, NewC.CCMask,
                                                MaskVal << ShiftVal,
                                                CmpVal << ShiftVal,
                                                SystemZICMP::UnsignedOnly))) {
-    AndOp0 = AndOp0.getOperand(0);
-    AndOp1 = DAG.getConstant(MaskVal << ShiftVal, AndOp0.getValueType());
+    NewC.Op0 = NewC.Op0.getOperand(0);
+    MaskVal <<= ShiftVal;
   } else {
-    NewCCMask = getTestUnderMaskCond(BitSize, C.CCMask, MaskVal, CmpVal,
-                                     C.ICmpType);
+    NewCCMask = getTestUnderMaskCond(BitSize, NewC.CCMask, MaskVal, CmpVal,
+                                     NewC.ICmpType);
     if (!NewCCMask)
       return;
   }
 
   // Go ahead and make the change.
   C.Opcode = SystemZISD::TM;
-  C.Op0 = AndOp0;
-  C.Op1 = AndOp1;
+  C.Op0 = NewC.Op0;
+  if (Mask && Mask->getZExtValue() == MaskVal)
+    C.Op1 = SDValue(Mask, 0);
+  else
+    C.Op1 = DAG.getConstant(MaskVal, C.Op0.getValueType());
   C.CCValid = SystemZ::CCMASK_TM;
   C.CCMask = NewCCMask;
 }
Index: test/CodeGen/SystemZ/int-cmp-47.ll
===================================================================
--- test/CodeGen/SystemZ/int-cmp-47.ll.orig
+++ test/CodeGen/SystemZ/int-cmp-47.ll
@@ -232,3 +232,112 @@ store:
 exit:
   ret void
 }
+
+; Check a case where TMHH can be used to implement a ult comparison.
+define void @f13(i64 %a) {
+; CHECK-LABEL: f13:
+; CHECK: tmhh %r2, 49152
+; CHECK: jno {{\.L.*}}
+; CHECK: br %r14
+entry:
+  %cmp = icmp ult i64 %a, 13835058055282163712
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}
+
+; And again with ule.
+define void @f14(i64 %a) {
+; CHECK-LABEL: f14:
+; CHECK: tmhh %r2, 49152
+; CHECK: jno {{\.L.*}}
+; CHECK: br %r14
+entry:
+  %cmp = icmp ule i64 %a, 13835058055282163711
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}
+
+; And again with ugt.
+define void @f15(i64 %a) {
+; CHECK-LABEL: f15:
+; CHECK: tmhh %r2, 49152
+; CHECK: jo {{\.L.*}}
+; CHECK: br %r14
+entry:
+  %cmp = icmp ugt i64 %a, 13835058055282163711
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}
+
+; And again with uge.
+define void @f16(i64 %a) {
+; CHECK-LABEL: f16:
+; CHECK: tmhh %r2, 49152
+; CHECK: jo {{\.L.*}}
+; CHECK: br %r14
+entry:
+  %cmp = icmp uge i64 %a, 13835058055282163712
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Decrease the constant from f13 to make TMHH invalid.
+define void @f17(i64 %a) {
+; CHECK-LABEL: f17:
+; CHECK-NOT: tmhh
+; CHECK: llihh {{%r[0-5]}}, 49151
+; CHECK-NOT: tmhh
+; CHECK: br %r14
+entry:
+  %cmp = icmp ult i64 %a, 13834776580305453056
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Check that we don't use TMHH just to test the top bit.
+define void @f18(i64 %a) {
+; CHECK-LABEL: f18:
+; CHECK-NOT: tmhh
+; CHECK: cgijhe %r2, 0,
+; CHECK: br %r14
+entry:
+  %cmp = icmp ult i64 %a, 9223372036854775808
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 1, i32 *@g
+  br label %exit
+
+exit:
+  ret void
+}

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