s390: Optimize LoadDoubleLiteral

R=joransiu@ca.ibm.com, bjaideep@ca.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2611773003
Cr-Commit-Position: refs/heads/master@{#42050}

src/s390/macro-assembler-s390.cc

@@ -4334,9 +4334,16 @@ void MacroAssembler::LoadDoubleLiteral(DoubleRegister result, uint64_t value,
   uint32_t lo_32 = static_cast<uint32_t>(value);
 
   // Load the 64-bit value into a GPR, then transfer it to FPR via LDGR
-  iihf(scratch, Operand(hi_32));
-  iilf(scratch, Operand(lo_32));
-  ldgr(result, scratch);
+  if (value == 0) {
+    lzdr(result);
+  } else if (lo_32 == 0) {
+    llihf(scratch, Operand(hi_32));
+    ldgr(result, scratch);
+  } else {
+    iihf(scratch, Operand(hi_32));
+    iilf(scratch, Operand(lo_32));
+    ldgr(result, scratch);
+  }
 }
 
 void MacroAssembler::LoadDoubleLiteral(DoubleRegister result, double value,
@@ -4347,13 +4354,9 @@ void MacroAssembler::LoadDoubleLiteral(DoubleRegister result, double value,
 
 void MacroAssembler::LoadFloat32Literal(DoubleRegister result, float value,
                                         Register scratch) {
-  uint32_t hi_32 = bit_cast<uint32_t>(value);
-  uint32_t lo_32 = 0;
-
-  // Load the 64-bit value into a GPR, then transfer it to FPR via LDGR
-  iihf(scratch, Operand(hi_32));
-  iilf(scratch, Operand(lo_32));
-  ldgr(result, scratch);
+  uint64_t int_val = static_cast<uint64_t>(bit_cast<uint32_t, float>(value))
+                     << 32;
+  LoadDoubleLiteral(result, int_val, scratch);
 }
 
 void MacroAssembler::CmpSmiLiteral(Register src1, Smi* smi, Register scratch) {