MIPS: Fix infinite loop in Math.pow(2,-2147483648)

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 47a0a8ea7930394875b406521881cda289432e48..e7ca6d02bee7fd8c80dda17b7a8809997679d92f 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -823,10 +823,14 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ Move(double_result, 1.0);
 
   // Get absolute value of exponent.
-  Label positive_exponent;
+  Label positive_exponent, bail_out;
   __ Branch(&positive_exponent, ge, scratch, Operand(zero_reg));
   __ Subu(scratch, zero_reg, scratch);
+  // Check when Subu overflows and we get negative result
+  // (happens only when input is MIN_INT)

[akos.palfi.imgtec, 2016/07/21 11:23:27]

Nit: please put period at the end of the sentence.

[ivica.bogosavljevic, 2016/07/22 14:45:07]

Acknowledged.

+  __ BranchShort(&bail_out, gt, zero_reg, Operand(scratch));

[akos.palfi.imgtec, 2016/07/21 11:23:27]

You should use Branch() instead of BranchShort().

[ivica.bogosavljevic, 2016/07/22 14:45:07]

Acknowledged.

   __ bind(&positive_exponent);
+  __ Assert(ge, kUnexpectedNegativeValue, scratch, Operand(zero_reg));
 
   Label while_true, no_carry, loop_end;
   __ bind(&while_true);
@@ -859,6 +863,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ cvt_d_w(double_exponent, single_scratch);
 
   // Returning or bailing out.
+  __ bind(&bail_out);
   __ push(ra);
   {
     AllowExternalCallThatCantCauseGC scope(masm);