diff options
| -rw-r--r-- | lib/Transforms/Scalar/Reassociate.cpp | 13 | ||||
| -rw-r--r-- | test/Transforms/Reassociate/subtest2.ll | 13 |
2 files changed, 21 insertions, 5 deletions
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp index d0537ea8c4..bec91dbe67 100644 --- a/lib/Transforms/Scalar/Reassociate.cpp +++ b/lib/Transforms/Scalar/Reassociate.cpp @@ -399,13 +399,16 @@ static bool ShouldBreakUpSubtract(Instruction *Sub) { return false; // Don't bother to break this up unless either the LHS is an associable add or - // if this is only used by one. - if (isReassociableOp(Sub->getOperand(0), Instruction::Add)) + // subtract or if this is only used by one. + if (isReassociableOp(Sub->getOperand(0), Instruction::Add) || + isReassociableOp(Sub->getOperand(0), Instruction::Sub)) return true; - if (isReassociableOp(Sub->getOperand(1), Instruction::Add)) + if (isReassociableOp(Sub->getOperand(1), Instruction::Add) || + isReassociableOp(Sub->getOperand(0), Instruction::Sub)) return true; - - if (Sub->hasOneUse() && isReassociableOp(Sub->use_back(), Instruction::Add)) + if (Sub->hasOneUse() && + (isReassociableOp(Sub->use_back(), Instruction::Add) || + isReassociableOp(Sub->use_back(), Instruction::Sub))) return true; return false; diff --git a/test/Transforms/Reassociate/subtest2.ll b/test/Transforms/Reassociate/subtest2.ll new file mode 100644 index 0000000000..c81e9b38de --- /dev/null +++ b/test/Transforms/Reassociate/subtest2.ll @@ -0,0 +1,13 @@ +; With sub reassociation, constant folding can eliminate the uses of %a. +; +; RUN: llvm-as < %s | opt -reassociate -instcombine | llvm-dis | grep %a | count 1 +; PR2047 + +define i32 @test(i32 %a, i32 %b, i32 %c) nounwind { +entry: + %tmp3 = sub i32 %a, %b ; <i32> [#uses=1] + %tmp5 = sub i32 %tmp3, %c ; <i32> [#uses=1] + %tmp7 = sub i32 %tmp5, %a ; <i32> [#uses=1] + ret i32 %tmp7 +} + |