[llvm] r185270 - InstCombine: Also turn selects fed by an and into arithmetic when the types don't match.

[Benjamin Kramer]

Author: d0k
Date: Sat Jun 29 16:17:04 2013
New Revision: 185270

URL: http://llvm.org/viewvc/llvm-project?rev=185270&view=rev
Log:
InstCombine: Also turn selects fed by an and into arithmetic when the types don't match.

Inserting a zext or trunc is sufficient. This pattern is somewhat common in
LLVM's pointer mangling code.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
    llvm/trunk/test/Transforms/InstCombine/select.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=185270&r1=185269&r2=185270&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Sat Jun 29 16:17:04 2013
@@ -662,7 +662,7 @@ static Value *foldSelectICmpAnd(const Se
                                 ConstantInt *FalseVal,
                                 InstCombiner::BuilderTy *Builder) {
   const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
-  if (!IC || !IC->isEquality())
+  if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
     return 0;
 
   if (!match(IC->getOperand(1), m_Zero()))
@@ -670,8 +670,7 @@ static Value *foldSelectICmpAnd(const Se
 
   ConstantInt *AndRHS;
   Value *LHS = IC->getOperand(0);
-  if (LHS->getType() != SI.getType() ||
-      !match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
+  if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
     return 0;
 
   // If both select arms are non-zero see if we have a select of the form
@@ -705,7 +704,13 @@ static Value *foldSelectICmpAnd(const Se
   unsigned ValZeros = ValC->getValue().logBase2();
   unsigned AndZeros = AndRHS->getValue().logBase2();
 
-  Value *V = LHS;
+  // If types don't match we can still convert the select by introducing a zext
+  // or a trunc of the 'and'. The trunc case requires that all of the truncated
+  // bits are zero, we can figure that out by looking at the 'and' mask.
+  if (AndZeros >= ValC->getBitWidth())
+    return 0;
+
+  Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
   if (ValZeros > AndZeros)
     V = Builder->CreateShl(V, ValZeros - AndZeros);
   else if (ValZeros < AndZeros)

Modified: llvm/trunk/test/Transforms/InstCombine/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/select.ll?rev=185270&r1=185269&r2=185270&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/select.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/select.ll Sat Jun 29 16:17:04 2013
@@ -985,3 +985,39 @@ define i32 @select_icmp_ne_0_and_8_or_10
   %select = select i1 %cmp, i32 %y, i32 %or
   ret i32 %select
 }
+
+define i32 @test65(i64 %x) {
+  %1 = and i64 %x, 16
+  %2 = icmp ne i64 %1, 0
+  %3 = select i1 %2, i32 40, i32 42
+  ret i32 %3
+
+; CHECK: @test65
+; CHECK: and i64 %x, 16
+; CHECK: trunc i64 %1 to i32
+; CHECK: lshr exact i32 %2, 3
+; CHECK: xor i32 %3, 42
+}
+
+define i32 @test66(i64 %x) {
+  %1 = and i64 %x, 4294967296
+  %2 = icmp ne i64 %1, 0
+  %3 = select i1 %2, i32 40, i32 42
+  ret i32 %3
+
+; CHECK: @test66
+; CHECK: select
+}
+
+define i32 @test67(i16 %x) {
+  %1 = and i16 %x, 4
+  %2 = icmp ne i16 %1, 0
+  %3 = select i1 %2, i32 40, i32 42
+  ret i32 %3
+
+; CHECK: @test67
+; CHECK: and i16 %x, 4
+; CHECK: zext i16 %1 to i32
+; CHECK: lshr exact i32 %2, 1
+; CHECK: xor i32 %3, 42
+}