[InstCombine] foldShiftIntoShiftInAnotherHandOfAndInICmp(): avoid constantexpr pitfail (PR42962)

Instead of matching value and then blindly casting to BinaryOperator
just to get the opcode, just match instruction and do no cast.

Fixes https://bugs.llvm.org/show_bug.cgi?id=42962

llvm-svn: 368554

2 files changed, 17 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 46294ad732a..22e02969d6a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3312,10 +3312,10 @@ foldShiftIntoShiftInAnotherHandOfAndInICmp(ICmpInst &I, const SimplifyQuery SQ,
 
   // Look for an 'and' of two (opposite) logical shifts.
   // Pick the single-use shift as XShift.
-  Value *XShift, *YShift;
+  Instruction *XShift, *YShift;
   if (!match(I.getOperand(0),
-             m_c_And(m_CombineAnd(m_AnyLogicalShift, m_Value(XShift)),
-                     m_CombineAnd(m_AnyLogicalShift, m_Value(YShift)))))
+             m_c_And(m_CombineAnd(m_AnyLogicalShift, m_Instruction(XShift)),
+                     m_CombineAnd(m_AnyLogicalShift, m_Instruction(YShift)))))
     return nullptr;
 
   // If YShift is a 'lshr', swap the shifts around.
@@ -3323,9 +3323,8 @@ foldShiftIntoShiftInAnotherHandOfAndInICmp(ICmpInst &I, const SimplifyQuery SQ,
     std::swap(XShift, YShift);
 
   // The shifts must be in opposite directions.
-  Instruction::BinaryOps XShiftOpcode =
-      cast<BinaryOperator>(XShift)->getOpcode();
-  if (XShiftOpcode == cast<BinaryOperator>(YShift)->getOpcode())
+  auto XShiftOpcode = XShift->getOpcode();
+  if (XShiftOpcode == YShift->getOpcode())
     return nullptr; // Do not care about same-direction shifts here.
 
   Value *X, *XShAmt, *Y, *YShAmt;
diff --git a/llvm/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll b/llvm/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll
index 55d268b9b77..9a2cfa5977a 100644
--- a/llvm/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll
+++ b/llvm/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll
@@ -667,3 +667,15 @@ define <2 x i1> @n38_overshift(<2 x i32> %x, <2 x i32> %y) {
   %t3 = icmp ne <2 x i32> %t2, <i32 0, i32 0>
   ret <2 x i1> %t3
 }
+
+; As usual, don't crash given constantexpr's :/
+@f.a = internal global i16 0
+define i1 @constantexpr() {
+entry:
+  %0 = load i16, i16* @f.a
+  %shr = ashr i16 %0, 1
+  %shr1 = ashr i16 %shr, zext (i1 icmp ne (i16 ptrtoint (i16* @f.a to i16), i16 1) to i16)
+  %and = and i16 %shr1, 1
+  %tobool = icmp ne i16 %and, 0
+  ret i1 %tobool
+}