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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/168451">168451</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2014-05-07 16:22:07 -0700 (Wed, 07 May 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>[X86] Emit BT instruction for single-bit tests.
<https://webkit.org/b/132650>
Implement test-bit-and-branch slightly more efficiently by using
BT + JC/JNC instead of TEST + JZ/JNZ when we're only testing for
a single bit.
Reviewed by Michael Saboff.
* assembler/MacroAssemblerX86Common.h:
(JSC::MacroAssemblerX86Common::singleBitIndex):
(JSC::MacroAssemblerX86Common::branchTest32):
* assembler/X86Assembler.h:
(JSC::X86Assembler::bt_i8r):
(JSC::X86Assembler::bt_i8m):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreassemblerMacroAssemblerX86Commonh">trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h</a></li>
<li><a href="#trunkSourceJavaScriptCoreassemblerX86Assemblerh">trunk/Source/JavaScriptCore/assembler/X86Assembler.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (168450 => 168451)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-05-07 23:06:32 UTC (rev 168450)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-05-07 23:22:07 UTC (rev 168451)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2014-05-07 Andreas Kling <akling@apple.com>
+
+ [X86] Emit BT instruction for single-bit tests.
+ <https://webkit.org/b/132650>
+
+ Implement test-bit-and-branch slightly more efficiently by using
+ BT + JC/JNC instead of TEST + JZ/JNZ when we're only testing for
+ a single bit.
+
+ Reviewed by Michael Saboff.
+
+ * assembler/MacroAssemblerX86Common.h:
+ (JSC::MacroAssemblerX86Common::singleBitIndex):
+ (JSC::MacroAssemblerX86Common::branchTest32):
+ * assembler/X86Assembler.h:
+ (JSC::X86Assembler::bt_i8r):
+ (JSC::X86Assembler::bt_i8m):
+
</ins><span class="cx"> 2014-05-07 Mark Lam <mark.lam@apple.com>
</span><span class="cx">
</span><span class="cx"> REGRESSION(r166678): Dromaeo/cssquery-dojo.html crashes regularly.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreassemblerMacroAssemblerX86Commonh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h (168450 => 168451)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h 2014-05-07 23:06:32 UTC (rev 168450)
+++ trunk/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h 2014-05-07 23:22:07 UTC (rev 168451)
</span><span class="lines">@@ -1163,14 +1163,65 @@
</span><span class="cx"> return Jump(m_assembler.jCC(x86Condition(cond)));
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ int singleBitIndex(unsigned mask)
+ {
+ switch (mask) {
+ case 0x00000001: return 0;
+ case 0x00000002: return 1;
+ case 0x00000004: return 2;
+ case 0x00000008: return 3;
+ case 0x00000010: return 4;
+ case 0x00000020: return 5;
+ case 0x00000040: return 6;
+ case 0x00000080: return 7;
+ case 0x00000100: return 8;
+ case 0x00000200: return 9;
+ case 0x00000400: return 10;
+ case 0x00000800: return 11;
+ case 0x00001000: return 12;
+ case 0x00002000: return 13;
+ case 0x00004000: return 14;
+ case 0x00008000: return 15;
+ case 0x00010000: return 16;
+ case 0x00020000: return 17;
+ case 0x00040000: return 18;
+ case 0x00080000: return 19;
+ case 0x00100000: return 20;
+ case 0x00200000: return 21;
+ case 0x00400000: return 22;
+ case 0x00800000: return 23;
+ case 0x01000000: return 24;
+ case 0x02000000: return 25;
+ case 0x04000000: return 26;
+ case 0x08000000: return 27;
+ case 0x10000000: return 28;
+ case 0x20000000: return 29;
+ case 0x40000000: return 30;
+ case 0x80000000: return 31;
+ default: return -1;
+ }
+ }
+
</ins><span class="cx"> Jump branchTest32(ResultCondition cond, RegisterID reg, TrustedImm32 mask = TrustedImm32(-1))
</span><span class="cx"> {
</span><ins>+ int bitIndex = singleBitIndex(mask.m_value);
+ if ((cond == Zero || cond == NonZero) && bitIndex != -1) {
+ m_assembler.bt_i8r(bitIndex, reg);
+ return Jump(m_assembler.jCC(cond == Zero ? X86Assembler::ConditionNC : X86Assembler::ConditionC));
+ }
+
</ins><span class="cx"> test32(cond, reg, mask);
</span><span class="cx"> return branch(cond);
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> Jump branchTest32(ResultCondition cond, Address address, TrustedImm32 mask = TrustedImm32(-1))
</span><span class="cx"> {
</span><ins>+ int bitIndex = singleBitIndex(mask.m_value);
+ if ((cond == Zero || cond == NonZero) && bitIndex != -1) {
+ m_assembler.bt_i8m(bitIndex, address.offset, address.base);
+ return Jump(m_assembler.jCC(cond == Zero ? X86Assembler::ConditionNC : X86Assembler::ConditionC));
+ }
+
</ins><span class="cx"> generateTest32(address, mask);
</span><span class="cx"> return Jump(m_assembler.jCC(x86Condition(cond)));
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreassemblerX86Assemblerh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/assembler/X86Assembler.h (168450 => 168451)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/assembler/X86Assembler.h 2014-05-07 23:06:32 UTC (rev 168450)
+++ trunk/Source/JavaScriptCore/assembler/X86Assembler.h 2014-05-07 23:22:07 UTC (rev 168451)
</span><span class="lines">@@ -278,6 +278,7 @@
</span><span class="cx"> OP_SETCC = 0x90,
</span><span class="cx"> OP2_3BYTE_ESCAPE = 0xAE,
</span><span class="cx"> OP2_IMUL_GvEv = 0xAF,
</span><ins>+ OP2_GROUP_BT = 0xBA,
</ins><span class="cx"> OP2_MOVZX_GvEb = 0xB6,
</span><span class="cx"> OP2_MOVSX_GvEb = 0xBE,
</span><span class="cx"> OP2_MOVZX_GvEw = 0xB7,
</span><span class="lines">@@ -336,6 +337,8 @@
</span><span class="cx"> GROUP14_OP_PSLLQ = 6,
</span><span class="cx"> GROUP14_OP_PSRLQ = 2,
</span><span class="cx">
</span><ins>+ GROUP_BT_OP_BT = 4,
+
</ins><span class="cx"> ESCAPE_DD_FSTP_doubleReal = 3,
</span><span class="cx"> } GroupOpcodeID;
</span><span class="cx">
</span><span class="lines">@@ -1221,6 +1224,18 @@
</span><span class="cx"> m_formatter.immediate8(imm);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ void bt_i8r(int bitIndex, RegisterID src)
+ {
+ m_formatter.twoByteOp(OP2_GROUP_BT, GROUP_BT_OP_BT, src);
+ m_formatter.immediate8(bitIndex);
+ }
+
+ void bt_i8m(int bitIndex, int offset, RegisterID base)
+ {
+ m_formatter.twoByteOp(OP2_GROUP_BT, GROUP_BT_OP_BT, base, offset);
+ m_formatter.immediate8(bitIndex);
+ }
+
</ins><span class="cx"> void setCC_r(Condition cond, RegisterID dst)
</span><span class="cx"> {
</span><span class="cx"> m_formatter.twoByteOp8(setccOpcode(cond), (GroupOpcodeID)0, dst);
</span></span></pre>
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