Merging r196267:

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r196267 | rsandifo | 2013-12-03 11:01:54 +0000 (Tue, 03 Dec 2013) | 12 lines

[SystemZ] Fix choice of known-zero mask in insertion optimization

The backend converts 64-bit ORs into subreg moves if the upper 32 bits
of one operand and the low 32 bits of the other are known to be zero.
It then tries to peel away redundant ANDs from the upper 32 bits.

Since AND masks are canonicalized to exclude known-zero bits,
the test ORs the mask and the known-zero bits together before
checking for redundancy.  The problem was that it was using the
wrong node when checking for known-zero bits, so could drop ANDs
that were still needed.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@196268 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 4a5fb42cbefc974d202ce5ef9110f2c68a8afc86..f6e18530f4a56e53fce3922e238a6144d31c2d99 100644 (file)
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1933,10 +1933,10 @@ SDValue SystemZTargetLowering::lowerOR(SDValue Op, SelectionDAG &DAG) const {
   // high 32 bits and just masks out low bits.  We can skip it if so.
   if (HighOp.getOpcode() == ISD::AND &&
       HighOp.getOperand(1).getOpcode() == ISD::Constant) {
-    ConstantSDNode *MaskNode = cast<ConstantSDNode>(HighOp.getOperand(1));
-    uint64_t Mask = MaskNode->getZExtValue() | Masks[High];
-    if ((Mask >> 32) == 0xffffffff)
-      HighOp = HighOp.getOperand(0);
+    SDValue HighOp0 = HighOp.getOperand(0);
+    uint64_t Mask = cast<ConstantSDNode>(HighOp.getOperand(1))->getZExtValue();
+    if (DAG.MaskedValueIsZero(HighOp0, APInt(64, ~(Mask | 0xffffffff))))
+      HighOp = HighOp0;
   }
 
   // Take advantage of the fact that all GR32 operations only change the

diff --git a/test/CodeGen/SystemZ/insert-06.ll b/test/CodeGen/SystemZ/insert-06.ll
index 8366b2c79791a9f99e58bd639fb3c6315268b3e1..edcd0c5dccd2ca90d9b467026540d6cc14d2cd44 100644 (file)
--- a/test/CodeGen/SystemZ/insert-06.ll
+++ b/test/CodeGen/SystemZ/insert-06.ll
@@ -165,3 +165,16 @@ define i64 @f13(i64 %a, i32 %b) {
   %or = or i64 %shift, %low
   ret i64 %or
 }
+
+; We previously wrongly removed the upper AND as dead.
+define i64 @f14(i64 %a, i64 %b) {
+; CHECK-LABEL: f14:
+; CHECK: risbg {{%r[0-5]}}, %r2, 6, 134, 0
+; CHECK: br %r14
+  %and1 = and i64 %a, 144115188075855872
+  %and2 = and i64 %b, 15
+  %or = or i64 %and1, %and2
+  %res = icmp eq i64 %or, 0
+  %ext = sext i1 %res to i64
+  ret i64 %ext
+}