Changeset 280609 in webkit

Timestamp:

Aug 3, 2021, 1:26:54 PM (5 years ago)

Author:

Yijia Huang

Message:

[ARM64] Use link register instead of pinning a register for materializing big load constants
​https://bugs.webkit.org/show_bug.cgi?id=228710

Reviewed by Mark Lam.

Previously, we pin a register as a temp for materializing a large constant that cannot fit in
Load/Store imm form. This is not efficient since the register allocator has one less register
to allocate from. To solve this problem, we should switch to using the link register as the temp
on ARM64.

• b3/B3Common.cpp:

(JSC::B3::linkRegister):
(JSC::B3::pinnedExtendedOffsetAddrRegister): Deleted.

• b3/B3Common.h:
• b3/air/AirAllocateRegistersAndStackAndGenerateCode.cpp:

(JSC::B3::Air::callFrameAddr):

• b3/air/AirCode.cpp:

(JSC::B3::Air::Code::Code):

• b3/air/AirLowerStackArgs.cpp:

(JSC::B3::Air::lowerStackArgs):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• b3/B3Common.cpp (modified) (1 diff)
• b3/B3Common.h (modified) (1 diff)
• b3/air/AirAllocateRegistersAndStackAndGenerateCode.cpp (modified) (1 diff)
• b3/air/AirCode.cpp (modified) (1 diff)
• b3/air/AirLowerStackArgs.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-08-03  Yijia Huang  <yijia_huang@apple.com>
+
+        [ARM64] Use link register instead of pinning a register for materializing big load constants
+        https://bugs.webkit.org/show_bug.cgi?id=228710
+
+        Reviewed by Mark Lam.
+
+        Previously, we pin a register as a temp for materializing a large constant that cannot fit in
+        Load/Store imm form. This is not efficient since the register allocator has one less register
+        to allocate from. To solve this problem, we should switch to using the link register as the temp
+        on ARM64.
+
+        * b3/B3Common.cpp:
+        (JSC::B3::linkRegister):
+        (JSC::B3::pinnedExtendedOffsetAddrRegister): Deleted.
+        * b3/B3Common.h:
+        * b3/air/AirAllocateRegistersAndStackAndGenerateCode.cpp:
+        (JSC::B3::Air::callFrameAddr):
+        * b3/air/AirCode.cpp:
+        (JSC::B3::Air::Code::Code):
+        * b3/air/AirLowerStackArgs.cpp:
+        (JSC::B3::Air::lowerStackArgs):
+
 2021-08-02  Yijia Huang  <yijia_huang@apple.com>
 

trunk/Source/JavaScriptCore/b3/B3Common.cpp

@@ -68 +68 @@
 }
 
-std::optional<GPRReg> pinnedExtendedOffsetAddrRegister()
+std::optional<GPRReg> linkRegister()
 {
 #if CPU(ARM64)
-    return MacroAssembler::dataTempRegister;
+    return MacroAssembler::linkRegister;
 #elif CPU(X86_64)
     return std::nullopt;

trunk/Source/JavaScriptCore/b3/B3Common.h

@@ -184 +184 @@
 }
 
-std::optional<GPRReg> pinnedExtendedOffsetAddrRegister();
+std::optional<GPRReg> linkRegister();
 
 } } // namespace JSC::B3

trunk/Source/JavaScriptCore/b3/air/AirAllocateRegistersAndStackAndGenerateCode.cpp

@@ -145 +145 @@
     }
 
-    ASSERT(pinnedExtendedOffsetAddrRegister());
+    ASSERT(linkRegister());
     auto addr = Arg::addr(Air::Tmp(GPRInfo::callFrameRegister), offsetFromFP);
     if (addr.isValidForm(Width64))
         return CCallHelpers::Address(GPRInfo::callFrameRegister, offsetFromFP);
-    GPRReg reg = *pinnedExtendedOffsetAddrRegister();
+    GPRReg reg = *linkRegister();
     jit.move(CCallHelpers::TrustedImmPtr(offsetFromFP), reg);
     jit.add64(GPRInfo::callFrameRegister, reg);

trunk/Source/JavaScriptCore/b3/air/AirCode.cpp

@@ -91 +91 @@
         });
 
-    if (auto reg = pinnedExtendedOffsetAddrRegister())
-        pinRegister(*reg);
-
     m_pinnedRegs.set(MacroAssembler::framePointerRegister);
 }

trunk/Source/JavaScriptCore/b3/air/AirLowerStackArgs.cpp

@@ -79 +79 @@
                         inst = Inst(inst.kind.opcode == Lea32 ? Add32 : Add64, inst.origin, Arg::imm(offset), base, inst.args[1]);
                     else {
-                        ASSERT(pinnedExtendedOffsetAddrRegister());
-                        Air::Tmp tmp = Air::Tmp(*pinnedExtendedOffsetAddrRegister());
+                        Air::Tmp tmp = Air::Tmp(*linkRegister());
                         Arg offsetArg = Arg::bigImm(offset);
                         insertionSet.insert(instIndex, Move, inst.origin, offsetArg, tmp);
@@ -129 +128 @@
                             return result;
 #if CPU(ARM64)
-                        ASSERT(pinnedExtendedOffsetAddrRegister());
-                        Air::Tmp tmp = Air::Tmp(*pinnedExtendedOffsetAddrRegister());
+                        Air::Tmp tmp = Air::Tmp(*linkRegister());
 
                         Arg largeOffset = Arg::isValidImmForm(offsetFromSP) ? Arg::imm(offsetFromSP) : Arg::bigImm(offsetFromSP);