Improve generated code for non-smi bit operations by...

src/codegen-ia32.cc

Index: src/codegen-ia32.cc
===================================================================
--- src/codegen-ia32.cc	(revision 1324)
+++ src/codegen-ia32.cc	(working copy)
@@ -4482,31 +4482,63 @@
       FloatingPointHelper::CheckFloatOperands(masm, &call_runtime, ebx);
       FloatingPointHelper::LoadFloatOperands(masm, ecx);
 
-      Label non_int32_operands, non_smi_result, skip_allocation;
-      // Reserve space for converted numbers.
-      __ sub(Operand(esp), Immediate(2 * kPointerSize));
+      Label non_smi_result, skip_allocation, operands_too_large;
 
-      // Check if right operand is int32.
-      __ fist_s(Operand(esp, 1 * kPointerSize));
-      __ fild_s(Operand(esp, 1 * kPointerSize));
-      __ fucompp();
+      // Make sure that the operands can be truncated into 64-bit
+      // integers. Otherwise, the fistt instruction will signal an IA
+      // exception which will cause us to overwrite the operand with
+      // zero.
+      __ push(Immediate(0x7fffffff));
+      __ push(Immediate(-1));
+      __ fild_d(Operand(esp, 0));
+      __ add(Operand(esp), Immediate(2 * kPointerSize));
+
+      // Convert the operands to absolute values before comparing
+      // against the limit.
+      __ fld(2);
+      __ fabs();
+      __ fld(2);
+      __ fabs();
+
+      // Do the comparison. If the operands are too large we go
+      // slow-case through the runtime system.
+      __ fucomp(2);
       __ fnstsw_ax();
       __ sahf();
-      __ j(not_zero, &non_int32_operands);
-      __ j(parity_even, &non_int32_operands);
-
-      // Check if left operand is int32.
-      __ fist_s(Operand(esp, 0 * kPointerSize));
-      __ fild_s(Operand(esp, 0 * kPointerSize));
+      __ j(above, &operands_too_large);
       __ fucompp();
       __ fnstsw_ax();
       __ sahf();
-      __ j(not_zero, &non_int32_operands);
-      __ j(parity_even, &non_int32_operands);
+      __ j(above, &operands_too_large);
 
+      // Reserve space for converted numbers.
+      __ sub(Operand(esp), Immediate(4 * kPointerSize));
+
+      // Convert right operand to int32.
+      Label done_right;
+      __ fnclex();
+      __ fisttp_d(Operand(esp, 2 * kPointerSize));

[Erik Corry, 2009/02/20 16:40:41]

This is an SSE3 instruction :-(.  I guess we can still use it but not in
snapshots and not without checking for SSE3.  See the Exceptions section of the
Intel documentation where it says it throws UD if the SSE3 bit is not set.

+      __ fnstsw_ax();
+      __ test(eax, Immediate(1));
+      __ j(zero, &done_right);
+      __ fnclex();
+      __ mov(Operand(esp, 2 * kPointerSize), Immediate(0));
+      __ bind(&done_right);
+
+      // Convert left operand to int32.
+      Label done_left;
+      __ fisttp_d(Operand(esp, 0 * kPointerSize));
+      __ fnstsw_ax();
+      __ test(eax, Immediate(1));
+      __ j(zero, &done_left);
+      __ mov(Operand(esp, 0 * kPointerSize), Immediate(0));
+      __ bind(&done_left);
+
       // Get int32 operands and perform bitop.
       __ pop(eax);
+      __ add(Operand(esp), Immediate(kPointerSize));
       __ pop(ecx);
+      __ add(Operand(esp), Immediate(kPointerSize));
       switch (op_) {
         case Token::BIT_OR:  __ or_(eax, Operand(ecx)); break;
         case Token::BIT_AND: __ and_(eax, Operand(ecx)); break;
@@ -4554,10 +4586,11 @@
         __ fstp_d(FieldOperand(eax, HeapNumber::kValueOffset));
         __ ret(2 * kPointerSize);
       }
-      __ bind(&non_int32_operands);
-      // Restore stacks and operands before calling runtime.
+
+      // Free ST(0) and ST(1) before calling runtime.
+      __ bind(&operands_too_large);
       __ ffree(0);
-      __ add(Operand(esp), Immediate(2 * kPointerSize));
+      __ ffree(1);
 
       // SHR should return uint32 - go to runtime for non-smi/negative result.
       if (op_ == Token::SHR) __ bind(&non_smi_result);