[PowerPC] Exploit the rlwinm instructions for "and" with constant

For now, PowerPC will using several instructions to get the constant and "and" it with the following case:

define i32 @test1(i32 %a) {
  %and = and i32 %a, -2
  ret i32 %and
}

However, we could exploit it with the rotate mask instructions.
               MB  ME
+----------------------+
|xxxxxxxxxxx00011111000|
+----------------------+
 0         32         64
Notice that, we can only do it if the MB is larger than 32 and MB <= ME as
RLWINM will replace the content of [0 - 32) with [32 - 64) even we didn't rotate it.

Differential Revision: https://reviews.llvm.org/D71829

llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h

@@ -82,6 +82,30 @@ static inline bool isRunOfOnes(unsigned Val, unsigned &MB, unsigned &ME) {
   return false;
 }
 
+static inline bool isRunOfOnes64(uint64_t Val, unsigned &MB, unsigned &ME) {
+  if (!Val)
+    return false;
+
+  if (isShiftedMask_64(Val)) {
+    // look for the first non-zero bit
+    MB = countLeadingZeros(Val);
+    // look for the first zero bit after the run of ones
+    ME = countLeadingZeros((Val - 1) ^ Val);
+    return true;
+  } else {
+    Val = ~Val; // invert mask
+    if (isShiftedMask_64(Val)) {
+      // effectively look for the first zero bit
+      ME = countLeadingZeros(Val) - 1;
+      // effectively look for the first one bit after the run of zeros
+      MB = countLeadingZeros((Val - 1) ^ Val) + 1;
+      return true;
+    }
+  }
+  // no run present
+  return false;
+}
+
 } // end namespace llvm
 
 // Generated files will use "namespace PPC". To avoid symbol clash,

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

@@ -4456,6 +4456,26 @@ bool PPCDAGToDAGISel::tryAndWithMask(SDNode *N) {
       CurDAG->SelectNodeTo(N, PPC::RLDICR, MVT::i64, Ops);
       return true;
     }
+
+    // It is not 16-bit imm that means we need two instructions at least if
+    // using "and" instruction. Try to exploit it with rotate mask instructions.
+    if (isRunOfOnes64(Imm64, MB, ME)) {
+      if (MB >= 32 && MB <= ME) {
+        //                MB  ME
+        // +----------------------+
+        // |xxxxxxxxxxx00011111000|
+        // +----------------------+
+        //  0         32         64
+        // We can only do it if the MB is larger than 32 and MB <= ME
+        // as RLWINM will replace the content of [0 - 32) with [32 - 64) even
+        // we didn't rotate it.
+        SDValue Ops[] = { Val, getI64Imm(0, dl), getI64Imm(MB - 32, dl),
+                          getI64Imm(ME - 32, dl) };
+        CurDAG->SelectNodeTo(N, PPC::RLWINM8, MVT::i64, Ops);
+        return true;
+      }
+      // TODO - handle it with rldicl + rldicl
+    }
   }
 
   return false;

llvm/test/CodeGen/PowerPC/and-mask.ll

@@ -5,10 +5,7 @@
 define i32 @test1(i32 %a) {
 ; CHECK-LABEL: test1:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    lis 4, 32767
-; CHECK-NEXT:    ori 4, 4, 65535
-; CHECK-NEXT:    sldi 4, 4, 1
-; CHECK-NEXT:    and 3, 3, 4
+; CHECK-NEXT:    rlwinm 3, 3, 0, 0, 30
 ; CHECK-NEXT:    blr
   %and = and i32 %a, -2
   ret i32 %and

llvm/test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll

@@ -7,12 +7,12 @@ define signext i32 @fn1(i32 %baz) {
   %2 = zext i32 %1 to i64
   %3 = shl i64 %2, 48
   %4 = ashr exact i64 %3, 48
-; CHECK: ANDI8o killed {{[^,]+}}, 65520, implicit-def dead $cr0
+; CHECK: RLWINM8 killed {{[^,]+}}, 0, 16, 27
 ; CHECK: CMPLDI
 ; CHECK: BCC
 
 ; CHECK: ANDI8o {{[^,]+}}, 65520, implicit-def $cr0
-; CHECK: COPY $cr0
+; CHECK: COPY killed $cr0
 ; CHECK: BCC
   %5 = icmp eq i64 %4, 0
   br i1 %5, label %foo, label %bar

llvm/test/CodeGen/PowerPC/popcnt-zext.ll

@@ -299,7 +299,7 @@ define i64 @popa_i16_i64(i16 %x) {
 ; FAST:       # %bb.0:
 ; FAST-NEXT:    clrldi 3, 3, 48
 ; FAST-NEXT:    popcntd 3, 3
-; FAST-NEXT:    andi. 3, 3, 16
+; FAST-NEXT:    rlwinm 3, 3, 0, 27, 27
 ; FAST-NEXT:    blr
 ;
 ; SLOW-LABEL: popa_i16_i64:
@@ -325,7 +325,7 @@ define i64 @popa_i16_i64(i16 %x) {
 ; SLOW-NEXT:    ori 4, 4, 257
 ; SLOW-NEXT:    mullw 3, 3, 4
 ; SLOW-NEXT:    srwi 3, 3, 24
-; SLOW-NEXT:    andi. 3, 3, 16
+; SLOW-NEXT:    rlwinm 3, 3, 0, 27, 27
 ; SLOW-NEXT:    blr
   %pop = call i16 @llvm.ctpop.i16(i16 %x)
   %z = zext i16 %pop to i64 ; SimplifyDemandedBits may turn zext (or sext) into aext