[JSC] ARM64 Imm should accept -UInt12

https://bugs.webkit.org/show_bug.cgi?id=257074
rdar://109596645

Reviewed by Keith Miller.

If ARM64 instructions is listed in AirOpcodes.opcode with Imm, this instruction supports
-UInt12 and UInt12 forms. We should correctly reflect it in Air::Arg::isValidImmForm.
This avoids unnecessary constant materialization for negative values, and it reduces register
pressures. Also ARM64 instruction selection can select cmn (cmp with negative UInt12) for example
with this change.

* Source/JavaScriptCore/assembler/MacroAssemblerARM64.h:
(JSC::MacroAssemblerARM64::branchAdd64):
(JSC::MacroAssemblerARM64::branchSub64):
* Source/JavaScriptCore/b3/B3MoveConstants.cpp:
* Source/JavaScriptCore/b3/air/AirArg.h:
(JSC::B3::Air::Arg::isValidImmForm):

Canonical link: https://commits.webkit.org/264296@main

Source/JavaScriptCore/assembler/MacroAssemblerARM64.h

@@ -4023,6 +4023,7 @@ class MacroAssemblerARM64 : public AbstractMacroAssembler<Assembler> {
 
     Jump branchAdd64(RelationalCondition cond, TrustedImm32 imm, RegisterID dest)
     {
+        // This is not supporting -imm.m_value UInt12. Thus we are not listing BranchAdd64 RelCond, Imm, Tmp in AirOpcode.opcodes.
         ASSERT(isUInt12(imm.m_value));
         m_assembler.add<64, S>(dest, dest, UInt12(imm.m_value));
         return Jump(makeBranch(cond));
@@ -4175,12 +4176,12 @@ class MacroAssemblerARM64 : public AbstractMacroAssembler<Assembler> {
 
     Jump branchSub64(RelationalCondition cond, TrustedImm32 imm, RegisterID dest)
     {
+        // This is not supporting -imm.m_value UInt12. Thus we are not listing BranchSub64 RelCond, Imm, Tmp in AirOpcode.opcodes.
         ASSERT(isUInt12(imm.m_value));
         m_assembler.sub<64, S>(dest, dest, UInt12(imm.m_value));
         return Jump(makeBranch(cond));
     }
 
-
     // Jumps, calls, returns
 
     // duplicate MacroAssembler's loadPtr for loading call targets.

Source/JavaScriptCore/b3/B3MoveConstants.cpp

@@ -217,8 +217,6 @@ class MoveConstants {
                         int64_t addendConst = addend->asInt();
                         if (Air::Arg::isValidImmForm(addendConst))
                             break;
-                        if (addendConst != INT64_MIN && Air::Arg::isValidImmForm(-addendConst))
-                            break;
                         Value* bestAddend = findBestConstant(
                             [&] (Value* candidateAddend) -> bool {
                                 if (candidateAddend->type() != addend->type())

Source/JavaScriptCore/b3/air/AirArg.h

@@ -1269,8 +1269,13 @@ class Arg {
     {
         if (isX86())
             return B3::isRepresentableAs<int32_t>(value);
-        if (isARM64())
-            return isUInt12(value);
+        if (isARM64()) {
+            if (isUInt12(value))
+                return true;
+            if (value == INT64_MIN)
+                return isUInt12(INT64_MIN);
+            return isUInt12(-value);
+        }
         if (isARM_THUMB2())
             return isValidARMThumb2Immediate(value);
         return false;