s390x: refactor CountLeadingZeros

Change-Id: Ic973b6342a6b91fe9068ee1ffe4e83a138fb2fa4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2679269Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/master@{#72564}

src/codegen/s390/macro-assembler-s390.cc

@@ -4697,6 +4697,21 @@ void TurboAssembler::CallForDeoptimization(Builtins::Name target, int,
 void TurboAssembler::Trap() { stop(); }
 void TurboAssembler::DebugBreak() { stop(); }
 
+void TurboAssembler::CountLeadingZerosU32(Register dst, Register src,
+                                          Register scratch_pair) {
+  llgfr(dst, src);
+  flogr(scratch_pair,
+        dst);  // will modify a register pair scratch and scratch + 1
+  AddS32(dst, scratch_pair, Operand(-32));
+}
+
+void TurboAssembler::CountLeadingZerosU64(Register dst, Register src,
+                                          Register scratch_pair) {
+  flogr(scratch_pair,
+        src);  // will modify a register pair scratch and scratch + 1
+  mov(dst, scratch_pair);
+}
+
 }  // namespace internal
 }  // namespace v8
 

src/codegen/s390/macro-assembler-s390.h

@@ -495,6 +495,9 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void Popcnt64(Register dst, Register src);
 #endif
 
+  // CountLeadingZeros will corrupt the scratch register pair (eg. r0:r1)
+  void CountLeadingZerosU32(Register dst, Register src, Register scratch_pair);
+  void CountLeadingZerosU64(Register dst, Register src, Register scratch_pair);
   void mov(Register dst, const Operand& src);
   void mov(Register dst, Register src);
 

src/compiler/backend/s390/code-generator-s390.cc

@@ -1891,16 +1891,12 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       ASSEMBLE_UNARY_OP(D_DInstr(lcdbr), nullInstr, nullInstr);
       break;
     case kS390_Cntlz32: {
-      __ llgfr(i.OutputRegister(), i.InputRegister(0));
-      __ flogr(r0, i.OutputRegister());
-      __ AddS32(i.OutputRegister(), r0, Operand(-32));
-      // No need to zero-ext b/c llgfr is done already
+      __ CountLeadingZerosU32(i.OutputRegister(), i.InputRegister(0), r0);
       break;
     }
 #if V8_TARGET_ARCH_S390X
     case kS390_Cntlz64: {
-      __ flogr(r0, i.InputRegister(0));
-      __ mov(i.OutputRegister(), r0);
+      __ CountLeadingZerosU64(i.OutputRegister(), i.InputRegister(0), r0);
       break;
     }
 #endif