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| author | Sanjay Patel <spatel@rotateright.com> | 2018-07-28 16:48:44 +0000 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2018-07-28 16:48:44 +0000 |
| commit | 818b253d3a33e4881b5378beee1fa72a0bece912 (patch) | |
| tree | 4e2a50682ef795d3c2989882d7a8ce112a2e9764 | |
| parent | 376051820d17cdc2feccb1878896d571db07f068 (diff) | |
| download | bcm5719-llvm-818b253d3a33e4881b5378beee1fa72a0bece912.tar.gz bcm5719-llvm-818b253d3a33e4881b5378beee1fa72a0bece912.zip | |
[InstCombine] try to fold 'sub' to 'not'
https://rise4fun.com/Alive/jDd
Patterns with add/sub combos can be improved using
'not' ops. This is better for analysis and may lead
to follow-on transforms because 'xor' and 'add' are
commutative/associative. It can also help codegen.
llvm-svn: 338200
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 8 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/sub-not.ll | 8 |
2 files changed, 11 insertions, 5 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index aa31e0d850d..e79bdf75d40 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -926,7 +926,13 @@ Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) { if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add)) return NV; - Value *X; + Value *X, *Y; + + // add (sub X, Y), -1 --> add (not Y), X + if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y)))) && + match(Op1, m_AllOnes())) + return BinaryOperator::CreateAdd(Builder.CreateNot(Y), X); + // zext(bool) + C -> bool ? C + 1 : C if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->getScalarSizeInBits() == 1) diff --git a/llvm/test/Transforms/InstCombine/sub-not.ll b/llvm/test/Transforms/InstCombine/sub-not.ll index 5fc42367dad..c4fbbe22f4e 100644 --- a/llvm/test/Transforms/InstCombine/sub-not.ll +++ b/llvm/test/Transforms/InstCombine/sub-not.ll @@ -40,8 +40,8 @@ define <2 x i8> @sub_not_vec(<2 x i8> %x, <2 x i8> %y) { define i8 @dec_sub(i8 %x, i8 %y) { ; CHECK-LABEL: @dec_sub( -; CHECK-NEXT: [[S:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]] -; CHECK-NEXT: [[R:%.*]] = add i8 [[S]], -1 +; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y:%.*]], -1 +; CHECK-NEXT: [[R:%.*]] = add i8 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i8 [[R]] ; %s = sub i8 %x, %y @@ -64,8 +64,8 @@ define i8 @dec_sub_extra_use(i8 %x, i8 %y) { define <2 x i8> @dec_sub_vec(<2 x i8> %x, <2 x i8> %y) { ; CHECK-LABEL: @dec_sub_vec( -; CHECK-NEXT: [[S:%.*]] = sub <2 x i8> [[X:%.*]], [[Y:%.*]] -; CHECK-NEXT: [[R:%.*]] = add <2 x i8> [[S]], <i8 -1, i8 undef> +; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i8> [[Y:%.*]], <i8 -1, i8 -1> +; CHECK-NEXT: [[R:%.*]] = add <2 x i8> [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret <2 x i8> [[R]] ; %s = sub <2 x i8> %x, %y |
