[llvm] 3052e47 - [InstCombine] matchBSwapOrBitReversem - recognise or(fshl(),fshl()) bswap patterns.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2020-10-25T10:17:45Z
New Revision: 3052e474eceb25e3699940d6a7270550eed66606

URL: https://github.com/llvm/llvm-project/commit/3052e474eceb25e3699940d6a7270550eed66606
DIFF: https://github.com/llvm/llvm-project/commit/3052e474eceb25e3699940d6a7270550eed66606.diff

LOG: [InstCombine] matchBSwapOrBitReversem - recognise or(fshl(),fshl()) bswap patterns.

I'm not certain InstCombinerImpl::matchBSwapOrBitReverse needs to filter the or(op0(),op1()) ops - there are just too many cases that recognizeBSwapOrBitReverseIdiom/collectBitParts handle now (and quickly).

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    llvm/test/Transforms/InstCombine/bswap.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 1e291fbe3f73..2911886636f9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2010,7 +2010,16 @@ Instruction *InstCombinerImpl::matchBSwapOrBitReverse(BinaryOperator &Or,
   bool OrWithAnds = match(Op0, m_And(m_Value(), m_Value())) ||
                     match(Op1, m_And(m_Value(), m_Value()));
 
-  if (!OrWithOrs && !OrWithShifts && !OrWithAnds)
+  // fshl(A,B,C) | D  and  A | fshl(B,C,D)          -> bswap if possible.
+  // fshr(A,B,C) | D  and  A | fshr(B,C,D)          -> bswap if possible.
+  bool OrWithFunnels = match(Op0, m_FShl(m_Value(), m_Value(), m_Value())) ||
+                       match(Op0, m_FShr(m_Value(), m_Value(), m_Value())) ||
+                       match(Op0, m_FShl(m_Value(), m_Value(), m_Value())) ||
+                       match(Op0, m_FShr(m_Value(), m_Value(), m_Value()));
+
+  // TODO: Do we need all these filtering checks or should we just rely on
+  // recognizeBSwapOrBitReverseIdiom + collectBitParts to reject them quickly?
+  if (!OrWithOrs && !OrWithShifts && !OrWithAnds && !OrWithFunnels)
     return nullptr;
 
   SmallVector<Instruction *, 4> Insts;

diff  --git a/llvm/test/Transforms/InstCombine/bswap.ll b/llvm/test/Transforms/InstCombine/bswap.ll
index f0a322d58913..c0893dd23b80 100644
--- a/llvm/test/Transforms/InstCombine/bswap.ll
+++ b/llvm/test/Transforms/InstCombine/bswap.ll
@@ -687,11 +687,7 @@ define i32 @funnel_binary(i32 %abcd) {
 
 define i32 @funnel_and(i32 %abcd) {
 ; CHECK-LABEL: @funnel_and(
-; CHECK-NEXT:    [[ZZCZ:%.*]] = and i32 [[ABCD:%.*]], 65280
-; CHECK-NEXT:    [[ZCZA:%.*]] = call i32 @llvm.fshl.i32(i32 [[ZZCZ]], i32 [[ABCD]], i32 8)
-; CHECK-NEXT:    [[ZBZZ:%.*]] = and i32 [[ABCD]], 16711680
-; CHECK-NEXT:    [[DZBZ:%.*]] = call i32 @llvm.fshl.i32(i32 [[ABCD]], i32 [[ZBZZ]], i32 24)
-; CHECK-NEXT:    [[DCBA:%.*]] = or i32 [[ZCZA]], [[DZBZ]]
+; CHECK-NEXT:    [[DCBA:%.*]] = call i32 @llvm.bswap.i32(i32 [[ABCD:%.*]])
 ; CHECK-NEXT:    ret i32 [[DCBA]]
 ;
   %zzcz = and i32 %abcd, 65280