diff options
| author | Sanjay Patel <spatel@rotateright.com> | 2019-06-20 22:55:28 +0000 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2019-06-20 22:55:28 +0000 |
| commit | b342f026a466e6faf331d91fced29db5d39796aa (patch) | |
| tree | fa1cc0b1ac4e2e11a5d7f88839f4af38df4d307c | |
| parent | 73986707bd57faab657c17acb6d219ed021f408a (diff) | |
| download | bcm5719-llvm-b342f026a466e6faf331d91fced29db5d39796aa.tar.gz bcm5719-llvm-b342f026a466e6faf331d91fced29db5d39796aa.zip | |
[InstSimplify] simplify power-of-2 (single bit set) sequences
As discussed in PR42314:
https://bugs.llvm.org/show_bug.cgi?id=42314
Improving the canonicalization for these patterns:
rL363956
...means we should adjust/enhance the related simplification.
https://rise4fun.com/Alive/w1cp
Name: isPow2 or zero
%x = and i32 %xx, 2048
%a = add i32 %x, -1
%r = and i32 %a, %x
=>
%r = i32 0
llvm-svn: 363997
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 10 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstSimplify/AndOrXor.ll | 10 |
2 files changed, 12 insertions, 8 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index ba76c5b0479..ce0b8a0fe64 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -1845,6 +1845,16 @@ static Value *SimplifyAndInst(Value *Op0, Value *Op1, const SimplifyQuery &Q, return Op1; } + // This is a similar pattern used for checking if a value is a power-of-2: + // (A - 1) & A --> 0 (if A is a power-of-2 or 0) + // A & (A - 1) --> 0 (if A is a power-of-2 or 0) + if (match(Op0, m_Add(m_Specific(Op1), m_AllOnes())) && + isKnownToBeAPowerOfTwo(Op1, Q.DL, /*OrZero*/ true, 0, Q.AC, Q.CxtI, Q.DT)) + return Constant::getNullValue(Op1->getType()); + if (match(Op1, m_Add(m_Specific(Op0), m_AllOnes())) && + isKnownToBeAPowerOfTwo(Op0, Q.DL, /*OrZero*/ true, 0, Q.AC, Q.CxtI, Q.DT)) + return Constant::getNullValue(Op0->getType()); + if (Value *V = simplifyAndOrOfCmps(Q, Op0, Op1, true)) return V; diff --git a/llvm/test/Transforms/InstSimplify/AndOrXor.ll b/llvm/test/Transforms/InstSimplify/AndOrXor.ll index e2c17e24028..a5c8108d0a5 100644 --- a/llvm/test/Transforms/InstSimplify/AndOrXor.ll +++ b/llvm/test/Transforms/InstSimplify/AndOrXor.ll @@ -93,10 +93,7 @@ define i64 @pow2b(i32 %x) { define i32 @pow2_decrement(i32 %p) { ; CHECK-LABEL: @pow2_decrement( -; CHECK-NEXT: [[X:%.*]] = shl i32 1, [[P:%.*]] -; CHECK-NEXT: [[A:%.*]] = add i32 [[X]], -1 -; CHECK-NEXT: [[R:%.*]] = and i32 [[A]], [[X]] -; CHECK-NEXT: ret i32 [[R]] +; CHECK-NEXT: ret i32 0 ; %x = shl i32 1, %p %a = add i32 %x, -1 @@ -106,10 +103,7 @@ define i32 @pow2_decrement(i32 %p) { define <2 x i32> @pow2_decrement_commute_vec(<2 x i32> %p) { ; CHECK-LABEL: @pow2_decrement_commute_vec( -; CHECK-NEXT: [[X:%.*]] = and <2 x i32> [[P:%.*]], <i32 2048, i32 2048> -; CHECK-NEXT: [[A:%.*]] = add <2 x i32> [[X]], <i32 -1, i32 -1> -; CHECK-NEXT: [[R:%.*]] = and <2 x i32> [[X]], [[A]] -; CHECK-NEXT: ret <2 x i32> [[R]] +; CHECK-NEXT: ret <2 x i32> zeroinitializer ; %x = and <2 x i32> %p, <i32 2048, i32 2048> %a = add <2 x i32> %x, <i32 -1, i32 -1> |
