PPC/s390: [masm] Shortcut some indirect external reference loads

Port 13fc4a1b

Original Commit Message:

    External references located within the isolate can be loaded as a
    fixed offset from the root register. This avoids one load from memory
    over the default indirect method (which reads from the external
    reference table).

R=jgruber@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I4a02973a0279517ab5247f4f9519b0e26168c444
Reviewed-on: https://chromium-review.googlesource.com/1097628Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#53680}

src/ppc/macro-assembler-ppc.cc

@@ -156,6 +156,15 @@ void TurboAssembler::LoadBuiltin(Register destination, int builtin_index) {
 
   LoadP(destination, MemOperand(kRootRegister, roots_to_builtins_offset), r0);
 }
+
+void TurboAssembler::LoadRootRegisterOffset(Register destination,
+                                            intptr_t offset) {
+  if (offset == 0) {
+    mr(destination, kRootRegister);
+  } else {
+    addi(destination, kRootRegister, Operand(offset));
+  }
+}
 #endif  // V8_EMBEDDED_BUILTINS
 
 void MacroAssembler::JumpToJSEntry(Register target) {

src/ppc/macro-assembler-ppc.h

@@ -439,6 +439,7 @@ class TurboAssembler : public TurboAssemblerBase {
   void LoadExternalReference(Register destination,
                              int reference_index) override;
   void LoadBuiltin(Register destination, int builtin_index) override;
+  void LoadRootRegisterOffset(Register destination, intptr_t offset) override;
 #endif  // V8_EMBEDDED_BUILTINS
 
   // Returns the size of a call in instructions. Note, the value returned is

src/s390/macro-assembler-s390.cc

@@ -151,6 +151,18 @@ void TurboAssembler::LoadBuiltin(Register destination, int builtin_index) {
 
   LoadP(destination, MemOperand(kRootRegister, roots_to_builtins_offset));
 }
+
+void TurboAssembler::LoadRootRegisterOffset(Register destination,
+                                            intptr_t offset) {
+  if (offset == 0) {
+    LoadRR(destination, kRootRegister);
+  } else if (is_uint12(offset)) {
+    la(destination, MemOperand(kRootRegister, offset));
+  } else {
+    DCHECK(is_int20(offset));
+    lay(destination, MemOperand(kRootRegister, offset));
+  }
+}
 #endif  // V8_EMBEDDED_BUILTINS
 
 void TurboAssembler::Jump(Register target, Condition cond) { b(cond, target); }

src/s390/macro-assembler-s390.h

@@ -182,6 +182,7 @@ class TurboAssembler : public TurboAssemblerBase {
   void LoadExternalReference(Register destination,
                              int reference_index) override;
   void LoadBuiltin(Register destination, int builtin_index) override;
+  void LoadRootRegisterOffset(Register destination, intptr_t offset) override;
 #endif  // V8_EMBEDDED_BUILTINS
 
   // Returns the size of a call in instructions.