[llvm] r314233 - [InstCombine] Remove one use restriction on the shift for calls to foldICmpAndShift.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Tue Sep 26 11:47:25 2017
New Revision: 314233

URL: http://llvm.org/viewvc/llvm-project?rev=314233&view=rev
Log:
[InstCombine] Remove one use restriction on the shift for calls to foldICmpAndShift.

If this transformation succeeds, we're going to remove our dependency on the shift by rewriting the and. So it doesn't matter how many uses the shift has.

This distributes the one use check to other transforms in foldICmpAndConstConst that do need it.

Differential Revision: https://reviews.llvm.org/D38206

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/icmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=314233&r1=314232&r2=314233&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Tue Sep 26 11:47:25 2017
@@ -1646,7 +1646,7 @@ Instruction *InstCombiner::foldICmpAndCo
   if (!match(And->getOperand(1), m_APInt(C2)))
     return nullptr;
 
-  if (!And->hasOneUse() || !And->getOperand(0)->hasOneUse())
+  if (!And->hasOneUse())
     return nullptr;
 
   // If the LHS is an 'and' of a truncate and we can widen the and/compare to
@@ -1658,7 +1658,7 @@ Instruction *InstCombiner::foldICmpAndCo
   // set or if it is an equality comparison. Extending a relational comparison
   // when we're checking the sign bit would not work.
   Value *W;
-  if (match(And->getOperand(0), m_Trunc(m_Value(W))) &&
+  if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
       (Cmp.isEquality() || (!C1->isNegative() && !C2->isNegative()))) {
     // TODO: Is this a good transform for vectors? Wider types may reduce
     // throughput. Should this transform be limited (even for scalars) by using
@@ -1680,7 +1680,7 @@ Instruction *InstCombiner::foldICmpAndCo
   // (icmp pred (and A, (or (shl 1, B), 1), 0))
   //
   // iff pred isn't signed
-  if (!Cmp.isSigned() && C1->isNullValue() &&
+  if (!Cmp.isSigned() && C1->isNullValue() && And->getOperand(0)->hasOneUse() &&
       match(And->getOperand(1), m_One())) {
     Constant *One = cast<Constant>(And->getOperand(1));
     Value *Or = And->getOperand(0);

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=314233&r1=314232&r2=314233&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Tue Sep 26 11:47:25 2017
@@ -1615,6 +1615,25 @@ define <2 x i1> @icmp_add_and_shr_ne_0_v
   ret <2 x i1> %tobool
 }
 
+; Variation of the above with an extra use of the shift
+define i1 @icmp_and_shr_multiuse(i32 %X) {
+; CHECK-LABEL: @icmp_and_shr_multiuse(
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], 240
+; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[X]], 496
+; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp ne i32 [[AND]], 224
+; CHECK-NEXT:    [[TOBOOL2:%.*]] = icmp ne i32 [[AND2]], 432
+; CHECK-NEXT:    [[AND3:%.*]] = and i1 [[TOBOOL]], [[TOBOOL2]]
+; CHECK-NEXT:    ret i1 [[AND3]]
+;
+  %shr = lshr i32 %X, 4
+  %and = and i32 %shr, 15
+  %and2 = and i32 %shr, 31 ; second use of the shift
+  %tobool = icmp ne i32 %and, 14
+  %tobool2 = icmp ne i32 %and2, 27
+  %and3 = and i1 %tobool, %tobool2
+  ret i1 %and3
+}
+
 ; PR16244
 define i1 @test71(i8* %x) {
 ; CHECK-LABEL: @test71(