Changeset 189136 in webkit for trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h

Timestamp:

Aug 28, 2015, 6:57:05 PM (10 years ago)

Author:

[email protected]

Message:

[JSC][x86] Improve the compare functions when comparing with zero
​https://bugs.webkit.org/show_bug.cgi?id=148536

Patch by Benjamin Poulain <​[email protected]> on 2015-08-28
Reviewed by Geoffrey Garen.

This patch has two parts:
1) The macro assembler gets an additional cmp->test optimization

for LessThan and GreaterThanOrEqual.
Instead of comparing the value with an immediate, test the value
with itself and use the flag.

2) Extend the DFG JIT optimization of compare.

In particular, use the same optimization in compileInt32Compare()
as we have in compilePeepHoleBooleanBranch().
The generator compileInt32Compare() is unfortunately very
common due to MoveHints placed between the Compare node and the Branch
node.

• assembler/MacroAssembler.h:

(JSC::MacroAssembler::compare32):

• assembler/MacroAssemblerX86Common.h:

(JSC::MacroAssemblerX86Common::branch32):
(JSC::MacroAssemblerX86Common::compare32):

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::compilePeepHoleBooleanBranch):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::compileInt32Compare):

File:

• trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h

@@ -1125 +1125 @@
     Jump branch32(RelationalCondition cond, RegisterID left, TrustedImm32 right)
     {
-        if (((cond == Equal) || (cond == NotEqual)) && !right.m_value)
+        if (!right.m_value && (cond == Equal || cond == NotEqual || cond == LessThan || cond == GreaterThanOrEqual)) {
+            ResultCondition resultCondition;
+            switch (cond) {
+            case Equal:
+                resultCondition = Zero;
+                break;
+            case NotEqual:
+                resultCondition = NonZero;
+                break;
+            case LessThan:
+                resultCondition = Signed;
+                break;
+            case GreaterThanOrEqual:
+                resultCondition = PositiveOrZero;
+                break;
+            default:
+                RELEASE_ASSERT_NOT_REACHED();
+            }
             m_assembler.testl_rr(left, left);
-        else
-            m_assembler.cmpl_ir(right.m_value, left);
+            return Jump(m_assembler.jCC(x86Condition(resultCondition)));
+        }
+        m_assembler.cmpl_ir(right.m_value, left);
         return Jump(m_assembler.jCC(x86Condition(cond)));
     }
@@ -1438 +1456 @@
     void compare32(RelationalCondition cond, RegisterID left, TrustedImm32 right, RegisterID dest)
     {
-        if (((cond == Equal) || (cond == NotEqual)) && !right.m_value)
+        if (!right.m_value && (cond == Equal || cond == NotEqual || cond == LessThan || cond == GreaterThanOrEqual)) {
+            ResultCondition resultCondition;
+            switch (cond) {
+            case Equal:
+                resultCondition = Zero;
+                break;
+            case NotEqual:
+                resultCondition = NonZero;
+                break;
+            case LessThan:
+                resultCondition = Signed;
+                break;
+            case GreaterThanOrEqual:
+                resultCondition = PositiveOrZero;
+                break;
+            default:
+                RELEASE_ASSERT_NOT_REACHED();
+            }
             m_assembler.testl_rr(left, left);
-        else
-            m_assembler.cmpl_ir(right.m_value, left);
+            set32(x86Condition(resultCondition), dest);
+            return;
+        }
+        m_assembler.cmpl_ir(right.m_value, left);
         set32(x86Condition(cond), dest);
     }