[InstCombine] foldAddWithConstant(): don't deal with non-immediate constants

All of the code that handles general constant here (other than the more
restrictive APInt-dealing code) expects that it is an immediate,
because otherwise we won't actually fold the constants, and increase
instruction count. And it isn't obvious why we'd be okay with
increasing the number of constant expressions,
those still will have to be run..

But after 2829094a8e252d04f13aabdf6f416c42a06af695
this could also cause endless combine loops.
So actually properly restrict this code to immediates.

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 7b33e29..70caf2f 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -864,7 +864,7 @@ static Instruction *foldNoWrapAdd(BinaryOperator &Add,
 Instruction *InstCombinerImpl::foldAddWithConstant(BinaryOperator &Add) {
   Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
   Constant *Op1C;
-  if (!match(Op1, m_Constant(Op1C)))
+  if (!match(Op1, m_ImmConstant(Op1C)))
     return nullptr;
 
   if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add))

diff --git a/llvm/test/Transforms/InstCombine/sub-from-sub.ll b/llvm/test/Transforms/InstCombine/sub-from-sub.ll
index 0669efe..636b851 100644 (file)
--- a/llvm/test/Transforms/InstCombine/sub-from-sub.ll
+++ b/llvm/test/Transforms/InstCombine/sub-from-sub.ll
@@ -202,3 +202,14 @@ define i32 @constantexpr2(i32 %x, i8* %y) unnamed_addr {
   %r = sub i32 ptrtoint (i8* @g1 to i32), %i0
   ret i32 %r
 }
+
+define i64 @pr49870(i64 %x) {
+; CHECK-LABEL: @pr49870(
+; CHECK-NEXT:    [[I0:%.*]] = xor i64 [[X:%.*]], -1
+; CHECK-NEXT:    [[R:%.*]] = add i64 [[I0]], ptrtoint (i8* @g0 to i64)
+; CHECK-NEXT:    ret i64 [[R]]
+;
+  %i0 = xor i64 %x, -1
+  %r = add i64 %i0, ptrtoint (i8* @g0 to i64)
+  ret i64 %r
+}