[PATCH] D47765: [PowerPC] reduce rotate in BitPermutationSelector

[Hiroshi Inoue via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL334011: [PowerPC] reduce rotate in BitPermutationSelector (authored by inouehrs, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D47765?vs=149915&id=149948#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D47765

Files:
  llvm/trunk/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
  llvm/trunk/test/CodeGen/PowerPC/bitfieldinsert.ll


Index: llvm/trunk/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
===================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ llvm/trunk/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -1161,6 +1161,10 @@
         return true;
       else if (NumGroups < Other.NumGroups)
         return false;
+      else if (RLAmt == 0 && Other.RLAmt != 0)
+        return true;
+      else if (RLAmt != 0 && Other.RLAmt == 0)
+        return false;
       else if (FirstGroupStartIdx < Other.FirstGroupStartIdx)
         return true;
       return false;
@@ -1374,7 +1378,9 @@
   }
 
   // Take all (SDValue, RLAmt) pairs and sort them by the number of groups
-  // associated with each. If there is a degeneracy, pick the one that occurs
+  // associated with each. If the number of groups are same, we prefer a group
+  // which does not require rotate, i.e. RLAmt is 0, to avoid the first rotate
+  // instruction. If there is a degeneracy, pick the one that occurs
   // first (in the final value).
   void collectValueRotInfo() {
     ValueRots.clear();
Index: llvm/trunk/test/CodeGen/PowerPC/bitfieldinsert.ll
===================================================================
--- llvm/trunk/test/CodeGen/PowerPC/bitfieldinsert.ll
+++ llvm/trunk/test/CodeGen/PowerPC/bitfieldinsert.ll
@@ -0,0 +1,33 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 < %s | FileCheck %s
+
+; bitfieldinsert32: Test for rlwimi
+; equivalent C code
+;   struct s32 {
+;   	int a:8;
+;   	int b:16;
+;   	int c:8;
+;   };
+;   void bitfieldinsert32(struct s32 *p, unsigned int v) {
+;   	p->b = v;
+;   }
+
+%struct.s32 = type { i32 }
+
+define void @bitfieldinsert32(%struct.s32* nocapture %p, i32 zeroext %v) {
+; CHECK-LABEL: @bitfieldinsert32
+; CHECK: lwz [[REG1:[0-9]+]], 0(3)
+; CHECK: rlwimi [[REG1]], 4, 8, 8, 23
+; CHECK: stw [[REG1]], 0(3)
+; CHECK: blr
+entry:
+  %0 = getelementptr inbounds %struct.s32, %struct.s32* %p, i64 0, i32 0
+  %bf.load = load i32, i32* %0, align 4
+  %bf.value = shl i32 %v, 8
+  %bf.shl = and i32 %bf.value, 16776960
+  %bf.clear = and i32 %bf.load, -16776961
+  %bf.set = or i32 %bf.clear, %bf.shl
+  store i32 %bf.set, i32* %0, align 4
+  ret void
+}
+


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