MIPS: Use PC realitive instructions on r6.

src/mips64/code-stubs-mips64.cc

Index: src/mips64/code-stubs-mips64.cc
diff --git a/src/mips64/code-stubs-mips64.cc b/src/mips64/code-stubs-mips64.cc
index af13405e09fa62e7374ccd8703be01f901e07387..36dfdc64594ffdea136c769482fb87a49753127a 100644
--- a/src/mips64/code-stubs-mips64.cc
+++ b/src/mips64/code-stubs-mips64.cc
@@ -1123,20 +1123,23 @@ void CEntryStub::Generate(MacroAssembler* masm) {
   // we can store the address on the stack to be able to find it again and
   // we never have to restore it, because it will not change.
   { Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm);
-    // This branch-and-link sequence is needed to find the current PC on mips,
-    // saved to the ra register.
-    // Use masm-> here instead of the double-underscore macro since extra
-    // coverage code can interfere with the proper calculation of ra.
+    int numInstructionsToJump;
     Label find_ra;
-    __ bal(&find_ra);  // bal exposes branch delay slot.
-    __ nop();
-    __ bind(&find_ra);
-
     // Adjust the value in ra to point to the correct return location, 2nd
     // instruction past the real call into C code (the jalr(t9)), and push it.
     // This is the return address of the exit frame.
-    const int kNumInstructionsToJump = 5;
-    __ Daddu(ra, ra, kNumInstructionsToJump * kInt32Size);
+    if (kArchVariant >= kMips64r6) {
+      numInstructionsToJump = 4;
+      __ addiupc(ra, numInstructionsToJump + 1);
+    } else {
+      numInstructionsToJump = 5;
+      // This branch-and-link sequence is needed to find the current PC on mips
+      // before r6, saved to the ra register.
+      __ bal(&find_ra);  // bal exposes branch delay slot.
+      __ Daddu(ra, ra, numInstructionsToJump * Instruction::kInstrSize);
+    }
+
+    __ bind(&find_ra);
     // This spot was reserved in EnterExitFrame.
     __ sd(ra, MemOperand(sp, result_stack_size));
     // Stack space reservation moved to the branch delay slot below.
@@ -1148,7 +1151,7 @@ void CEntryStub::Generate(MacroAssembler* masm) {
     // Set up sp in the delay slot.
     __ daddiu(sp, sp, -kCArgsSlotsSize);
     // Make sure the stored 'ra' points to this position.
-    DCHECK_EQ(kNumInstructionsToJump,
+    DCHECK_EQ(numInstructionsToJump,
               masm->InstructionsGeneratedSince(&find_ra));
   }
   if (result_size() > 2) {