PPC/s390: [nojit] Change builtin pointers to use Smis underneath

Port fa3cbf60

Original Commit Message:

    This changes Torque's builtin pointers to use a Smi representation
    underneath instead of storing the Code target object. Callsites look
    up the target entry point through IsolateData::builtin_entry_table.

    The notable effect of this CL is that builtin pointer calls no longer
    call any on-heap Code.

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

Change-Id: I49bb08de916fd93e576936a56b0e1a0e21072289
Reviewed-on: https://chromium-review.googlesource.com/c/1394301Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#58530}

src/ppc/macro-assembler-ppc.cc

@@ -3024,8 +3024,18 @@ void TurboAssembler::JumpIfLessThan(Register x, int32_t y, Label* dest) {
 }
 
 void TurboAssembler::CallBuiltinPointer(Register builtin_pointer) {
+  STATIC_ASSERT(kSystemPointerSize == 8);
+  STATIC_ASSERT(kSmiShiftSize == 31);
+  STATIC_ASSERT(kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTag == 0);
+
+  // The builtin_pointer register contains the builtin index as a Smi.
+  // Untagging is folded into the indexing operand below.
+  ShiftRightArithImm(builtin_pointer, builtin_pointer,
+                     kSmiShift - kSystemPointerSizeLog2);
   addi(builtin_pointer, builtin_pointer,
-      Operand(Code::kHeaderSize - kHeapObjectTag));
+      Operand(IsolateData::builtin_entry_table_offset()));
+  LoadPX(builtin_pointer, MemOperand(kRootRegister, builtin_pointer));
   Call(builtin_pointer);
 }
 

src/s390/macro-assembler-s390.cc

@@ -4393,8 +4393,18 @@ void TurboAssembler::JumpIfLessThan(Register x, int32_t y, Label* dest) {
 }
 
 void TurboAssembler::CallBuiltinPointer(Register builtin_pointer) {
+  STATIC_ASSERT(kSystemPointerSize == 8);
+  STATIC_ASSERT(kSmiShiftSize == 31);
+  STATIC_ASSERT(kSmiTagSize == 1);
+  STATIC_ASSERT(kSmiTag == 0);
+
+  // The builtin_pointer register contains the builtin index as a Smi.
+  // Untagging is folded into the indexing operand below.
+  ShiftRightArithP(builtin_pointer, builtin_pointer,
+                   Operand(kSmiShift - kSystemPointerSizeLog2));
   AddP(builtin_pointer, builtin_pointer,
-      Operand(Code::kHeaderSize - kHeapObjectTag));
+      Operand(IsolateData::builtin_entry_table_offset()));
+  LoadP(builtin_pointer, MemOperand(kRootRegister, builtin_pointer));
   Call(builtin_pointer);
 }