[llvm] r306980 - [InstCombine] look through bswap/bitreverse for equality comparisons

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Sun Jul  2 07:34:50 2017
New Revision: 306980

URL: http://llvm.org/viewvc/llvm-project?rev=306980&view=rev
Log:
[InstCombine] look through bswap/bitreverse for equality comparisons

I noticed this missed bswap optimization in the CGP memcmp() expansion, 
and then I saw that we don't have the fold in InstCombine.

Differential Revision: https://reviews.llvm.org/D34763

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/icmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=306980&r1=306979&r2=306980&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Jul  2 07:34:50 2017
@@ -3438,6 +3438,15 @@ Instruction *InstCombiner::foldICmpEqual
     }
   }
 
+  // If both operands are byte-swapped or bit-reversed, just compare the
+  // original values.
+  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
+  // and handle more intrinsics.
+  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
+      (match(Op0, m_Intrinsic<Intrinsic::bitreverse>(m_Value(A))) &&
+       match(Op1, m_Intrinsic<Intrinsic::bitreverse>(m_Value(B)))))
+    return new ICmpInst(Pred, A, B);
+
   return nullptr;
 }
 

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=306980&r1=306979&r2=306980&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Sun Jul  2 07:34:50 2017
@@ -2979,9 +2979,7 @@ declare i32 @llvm.bswap.i32(i32)
 
 define i1 @bswap_ne(i32 %x, i32 %y) {
 ; CHECK-LABEL: @bswap_ne(
-; CHECK-NEXT:    [[SWAPX:%.*]] = call i32 @llvm.bswap.i32(i32 %x)
-; CHECK-NEXT:    [[SWAPY:%.*]] = call i32 @llvm.bswap.i32(i32 %y)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[SWAPX]], [[SWAPY]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %swapx = call i32 @llvm.bswap.i32(i32 %x)
@@ -2994,9 +2992,7 @@ declare <8 x i16> @llvm.bswap.v8i16(<8 x
 
 define <8 x i1> @bswap_vec_eq(<8 x i16> %x, <8 x i16> %y) {
 ; CHECK-LABEL: @bswap_vec_eq(
-; CHECK-NEXT:    [[SWAPX:%.*]] = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %x)
-; CHECK-NEXT:    [[SWAPY:%.*]] = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %y)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <8 x i16> [[SWAPX]], [[SWAPY]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <8 x i16> %x, %y
 ; CHECK-NEXT:    ret <8 x i1> [[CMP]]
 ;
   %swapx = call <8 x i16> @llvm.bswap.v8i16(<8 x i16> %x)
@@ -3009,9 +3005,7 @@ declare i64 @llvm.bitreverse.i64(i64)
 
 define i1 @bitreverse_eq(i64 %x, i64 %y) {
 ; CHECK-LABEL: @bitreverse_eq(
-; CHECK-NEXT:    [[REVX:%.*]] = call i64 @llvm.bitreverse.i64(i64 %x)
-; CHECK-NEXT:    [[REVY:%.*]] = call i64 @llvm.bitreverse.i64(i64 %y)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[REVX]], [[REVY]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %revx = call i64 @llvm.bitreverse.i64(i64 %x)
@@ -3024,9 +3018,7 @@ declare <8 x i16> @llvm.bitreverse.v8i16
 
 define <8 x i1> @bitreverse_vec_ne(<8 x i16> %x, <8 x i16> %y) {
 ; CHECK-LABEL: @bitreverse_vec_ne(
-; CHECK-NEXT:    [[REVX:%.*]] = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %x)
-; CHECK-NEXT:    [[REVY:%.*]] = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %y)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <8 x i16> [[REVX]], [[REVY]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <8 x i16> %x, %y
 ; CHECK-NEXT:    ret <8 x i1> [[CMP]]
 ;
   %revx = call <8 x i16> @llvm.bitreverse.v8i16(<8 x i16> %x)