[llvm] r368518 - [InstCombine] Shift amount reassociation in bittest: drop pointless one-use restriction

[Roman Lebedev via llvm-commits]

Author: lebedevri
Date: Sat Aug 10 12:28:44 2019
New Revision: 368518

URL: http://llvm.org/viewvc/llvm-project?rev=368518&view=rev
Log:
[InstCombine] Shift amount reassociation in bittest: drop pointless one-use restriction

That one-use restriction is not needed for correctness - we have already
ensured that one of the shifts will go away, so we know we won't increase
the instruction count. So there is no need for that restriction.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=368518&r1=368517&r2=368518&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sat Aug 10 12:28:44 2019
@@ -3318,8 +3318,8 @@ foldShiftIntoShiftInAnotherHandOfAndInIC
                      m_CombineAnd(m_AnyLogicalShift, m_Value(YShift)))))
     return nullptr;
 
-  // If YShift is a single-use 'lshr', swap the shifts around.
-  if (match(YShift, m_OneUse(m_AnyLShr)))
+  // If YShift is a 'lshr', swap the shifts around.
+  if (match(YShift, m_AnyLShr))
     std::swap(XShift, YShift);
 
   // The shifts must be in opposite directions.

Modified: llvm/trunk/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll?rev=368518&r1=368517&r2=368518&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll Sat Aug 10 12:28:44 2019
@@ -279,8 +279,8 @@ define i1 @t18_const_oneuse0(i32 %x, i32
 ; CHECK-LABEL: @t18_const_oneuse0(
 ; CHECK-NEXT:    [[T0:%.*]] = lshr i32 [[X:%.*]], 1
 ; CHECK-NEXT:    call void @use32(i32 [[T0]])
-; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 [[Y:%.*]], 2
-; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[X]], 2
+; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[TMP2]], 0
 ; CHECK-NEXT:    ret i1 [[TMP3]]
 ;
@@ -585,8 +585,8 @@ define i1 @t34_commutativity0_oneuse0(i3
 ; CHECK-NEXT:    [[Y:%.*]] = call i32 @gen32()
 ; CHECK-NEXT:    [[T0:%.*]] = lshr i32 [[X:%.*]], 1
 ; CHECK-NEXT:    call void @use32(i32 [[T0]])
-; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 [[Y]], 2
-; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[X]], 2
+; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[Y]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[TMP2]], 0
 ; CHECK-NEXT:    ret i1 [[TMP3]]
 ;
@@ -622,8 +622,8 @@ define i1 @t36_commutativity1_oneuse0(i3
 ; CHECK-NEXT:    [[X:%.*]] = call i32 @gen32()
 ; CHECK-NEXT:    [[T0:%.*]] = lshr i32 [[X]], 1
 ; CHECK-NEXT:    call void @use32(i32 [[T0]])
-; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 [[Y:%.*]], 2
-; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[X]], 2
+; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[TMP2]], 0
 ; CHECK-NEXT:    ret i1 [[TMP3]]
 ;