[llvm] r354499 - Revert r354498 "[X86] Add test case to show missed opportunity to remove an explicit AND on the bit position from BT when it has known zeros."

[Craig Topper via llvm-commits]

Author: ctopper
Date: Wed Feb 20 10:47:26 2019
New Revision: 354499

URL: http://llvm.org/viewvc/llvm-project?rev=354499&view=rev
Log:
Revert r354498 "[X86] Add test case to show missed opportunity to remove an explicit AND on the bit position from BT when it has known zeros."

I accidentally committed more than just the test.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/test/CodeGen/X86/bt.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=354499&r1=354498&r2=354499&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Wed Feb 20 10:47:26 2019
@@ -2102,13 +2102,9 @@ SDValue SelectionDAG::GetDemandedBits(SD
     break;
   case ISD::AND: {
     // X & -1 -> X (ignoring bits which aren't demanded).
-    // Also handle the case where masked out bits in X are known to be zero.
-    if (ConstantSDNode *RHSC = isConstOrConstSplat(V.getOperand(1))) {
-      const APInt &AndVal = RHSC->getAPIntValue();
-      if (Mask.isSubsetOf(AndVal) ||
-          Mask.isSubsetOf(computeKnownBits(V.getOperand(0)).Zero | AndVal))
-        return V.getOperand(0);
-    }
+    ConstantSDNode *AndVal = isConstOrConstSplat(V.getOperand(1));
+    if (AndVal && Mask.isSubsetOf(AndVal->getAPIntValue()))
+      return V.getOperand(0);
     break;
   }
   case ISD::ANY_EXTEND: {

Modified: llvm/trunk/test/CodeGen/X86/bt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/bt.ll?rev=354499&r1=354498&r2=354499&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/bt.ll (original)
+++ llvm/trunk/test/CodeGen/X86/bt.ll Wed Feb 20 10:47:26 2019
@@ -1144,32 +1144,3 @@ define void @demanded_i32(i32* nocapture
 ; <label>:16:
   ret void
 }
-
-; Make sure we can simplify bt when the shift amount has known zeros in it
-; which cause the and mask to have bits removed.
-define zeroext i1 @demanded_with_known_zeroes(i32 %bit, i32 %bits) {
-; X86-LABEL: demanded_with_known_zeroes:
-; X86:       # %bb.0: # %entry
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    movb {{[0-9]+}}(%esp), %cl
-; X86-NEXT:    shlb $2, %cl
-; X86-NEXT:    movzbl %cl, %ecx
-; X86-NEXT:    btl %ecx, %eax
-; X86-NEXT:    setb %al
-; X86-NEXT:    retl
-;
-; X64-LABEL: demanded_with_known_zeroes:
-; X64:       # %bb.0: # %entry
-; X64-NEXT:    shlb $2, %dil
-; X64-NEXT:    movzbl %dil, %eax
-; X64-NEXT:    btl %eax, %esi
-; X64-NEXT:    setb %al
-; X64-NEXT:    retq
-entry:
-  %bit2 = shl i32 %bit, 2
-  %and = and i32 %bit2, 31
-  %shl = shl i32 1, %and
-  %and1 = and i32 %shl, %bits
-  %tobool = icmp ne i32 %and1, 0
-  ret i1 %tobool
-}