ARM: Fix comparison of NaN values....

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
===================================================================
--- src/arm/lithium-codegen-arm.cc	(revision 6218)
+++ src/arm/lithium-codegen-arm.cc	(working copy)
@@ -1076,8 +1076,17 @@
     EmitBranch(true_block, false_block, nz);
   } else if (r.IsDouble()) {
     DoubleRegister reg = ToDoubleRegister(instr->input());
+    Register scratch = scratch0();
+
+    // Test for the double value. Zero and NaN are false.
+    // Clear the Invalid cumulative exception flags.

[Søren Thygesen Gjesse, 2011/01/07 11:44:32]

I will suggest a macro assembler instruction for this:

__ ClearFPCSRBit(kVFPInvalidExceptionBit, scratch);

[Alexandre, 2011/01/07 18:34:49]

Added the ClearFPSCRBits Masm instruction.
On 2011/01/07 11:44:32, Søren Gjesse wrote:

+    __ vmrs(scratch);
+    __ bic(scratch, scratch, Operand(kVFPInvalidExceptionBit));
+    __ vmsr(scratch);
     __ vcmp(reg, 0.0);
-    __ vmrs(pc);  // Move vector status bits to normal status bits.
+    __ vmrs(scratch);  // Retrieve the exception and status flags.
+    // Check for zero or an invalid exception.
+    __ tst(scratch, Operand(kVFPZConditionFlagBit | kVFPInvalidExceptionBit));
     EmitBranch(true_block, false_block, ne);
   } else {
     ASSERT(r.IsTagged());
@@ -1104,7 +1113,7 @@
       __ tst(reg, Operand(kSmiTagMask));
       __ b(eq, true_label);
 
-      // Test for double values. Zero is false.
+      // Test for double values. Zero and NaN are false.
       Label call_stub;
       DoubleRegister dbl_scratch = d0;
       Register scratch = scratch0();
@@ -1114,9 +1123,15 @@
       __ b(ne, &call_stub);
       __ sub(ip, reg, Operand(kHeapObjectTag));
       __ vldr(dbl_scratch, ip, HeapNumber::kValueOffset);
+      // Clear the Invalid cumulative exception flags.

[Søren Thygesen Gjesse, 2011/01/07 11:44:32]

Ditto.

[Alexandre, 2011/01/07 18:34:49]

Used the new pseudo instruction.
On 2011/01/07 11:44:32, Søren Gjesse wrote:

+      __ vmrs(scratch);
+      __ bic(scratch, scratch, Operand(kVFPInvalidExceptionBit));
+      __ vmsr(scratch);
       __ vcmp(dbl_scratch, 0.0);
-      __ vmrs(pc);  // Move vector status bits to normal status bits.
-      __ b(eq, false_label);
+      __ vmrs(scratch);  // Retrieve the exception and status flags.
+      // Check for zero or an invalid exception.
+      __ tst(scratch, Operand(kVFPZConditionFlagBit | kVFPInvalidExceptionBit));
+      __ b(ne, false_label);
       __ b(true_label);
 
       // The conversion stub doesn't cause garbage collections so it's