[PATCH] D101235: [InstCombine] ctpop(rot(X)) -> ctpop(X)

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 created this revision.
xbolva00 added a reviewer: nikic.
Herald added a subscriber: hiraditya.
xbolva00 requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Proof:
https://alive2.llvm.org/ce/z/ss2zyt - rotl
https://alive2.llvm.org/ce/z/ZM7Aue - rotr


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101235

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/ctpop.ll


Index: llvm/test/Transforms/InstCombine/ctpop.ll
===================================================================
--- llvm/test/Transforms/InstCombine/ctpop.ll
+++ llvm/test/Transforms/InstCombine/ctpop.ll
@@ -203,11 +203,11 @@
 
 define i32 @ctpop_add_no_common_bits(i32 %a, i32 %b) {
 ; CHECK-LABEL: @ctpop_add_no_common_bits(
-; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.fshl.i32(i32 [[B:%.*]], i32 [[B]], i32 16)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.fshl.i32(i32 [[A:%.*]], i32 [[B:%.*]], i32 16)
 ; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.ctpop.i32(i32 [[TMP1]]), !range [[RNG1]]
 ; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
-  %shl16 = shl i32 %b, 16
+  %shl16 = shl i32 %a, 16
   %ctpop1 = tail call i32 @llvm.ctpop.i32(i32 %shl16)
   %lshl16 = lshr i32 %b, 16
   %ctpop2 = tail call i32 @llvm.ctpop.i32(i32 %lshl16)
@@ -266,3 +266,26 @@
   %res = add <2 x i32> %ctpop1, %ctpop2
   ret <2 x i32> %res
 }
+
+define i8 @ctpop_rotate_left(i8 %a, i8 %amt)  {
+; CHECK-LABEL: @ctpop_rotate_left(
+; CHECK-NEXT:    [[CTPOP:%.*]] = tail call i8 @llvm.ctpop.i8(i8 [[A:%.*]]), !range [[RNG0]]
+; CHECK-NEXT:    ret i8 [[CTPOP]]
+;
+  %rotl = tail call i8 @llvm.fshl.i8(i8 %a, i8 %a, i8 %amt)
+  %ctpop = tail call i8 @llvm.ctpop.i8(i8 %rotl)
+  ret i8 %ctpop
+}
+
+define i8 @ctpop_rotate_right(i8 %a, i8 %amt)  {
+; CHECK-LABEL: @ctpop_rotate_right(
+; CHECK-NEXT:    [[CTPOP:%.*]] = tail call i8 @llvm.ctpop.i8(i8 [[A:%.*]]), !range [[RNG0]]
+; CHECK-NEXT:    ret i8 [[CTPOP]]
+;
+  %rotr = tail call i8 @llvm.fshr.i8(i8 %a, i8 %a, i8 %amt)
+  %ctpop = tail call i8 @llvm.ctpop.i8(i8 %rotr)
+  ret i8 %ctpop
+}
+
+declare i8 @llvm.fshl.i8(i8, i8, i8)
+declare i8 @llvm.fshr.i8(i8, i8, i8)
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -504,6 +504,11 @@
   if (match(Op0, m_BitReverse(m_Value(X))) || match(Op0, m_BSwap(m_Value(X))))
     return IC.replaceOperand(II, 0, X);
 
+  // ctpop(rot(x)) -> ctpop(x)
+  if (match(Op0, m_FShl(m_Value(X), m_Specific(X), m_Value())) ||
+      match(Op0, m_FShr(m_Value(X), m_Specific(X), m_Value())))
+    return IC.replaceOperand(II, 0, X);
+
   // ctpop(x | -x) -> bitwidth - cttz(x, false)
   if (Op0->hasOneUse() &&
       match(Op0, m_c_Or(m_Value(X), m_Neg(m_Deferred(X))))) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D101235.340289.patch
Type: text/x-patch
Size: 2436 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210424/623bf81f/attachment.bin>