AArch64: Add support for CHelper in PrivateLinkage

This commit adds support for CHelper in ARM64PrivateLinkage, which passes the VM thread as the implicit first argument.
pshipton · Sep 11, 2020 · 0cb4f56 · 0cb4f56
1 parent 5ef8df8
commit 0cb4f56
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Showing 2 changed files with 28 additions and 4 deletions.
diff --git a/runtime/codert_vm/arm64nathelp.m4 b/runtime/codert_vm/arm64nathelp.m4
@@ -178,9 +178,9 @@ define({NEW_DUAL_MODE_HELPER},{
 	ret x0
 .L_old_slow_$1:
 	RESTORE_C_NONVOLATILE_REGS
+	SWITCH_TO_JAVA_STACK
 .L_done_$1:
 	RESTORE_FPLR
-	SWITCH_TO_JAVA_STACK
 	ldr x0,[J9VMTHREAD,{#}J9TR_VMThread_returnValue]
 	ret
 	END_PROC($1)
@@ -201,9 +201,9 @@ define({NEW_DUAL_MODE_HELPER_NO_RETURN_VALUE},{
 	ret x0
 .L_old_slow_$1:
 	RESTORE_C_NONVOLATILE_REGS
+	SWITCH_TO_JAVA_STACK
 .L_done_$1:
 	RESTORE_FPLR
-	SWITCH_TO_JAVA_STACK
 	ret
 	END_PROC($1)
 })

diff --git a/runtime/compiler/aarch64/codegen/ARM64PrivateLinkage.cpp b/runtime/compiler/aarch64/codegen/ARM64PrivateLinkage.cpp
@@ -842,6 +842,7 @@ int32_t J9::ARM64::PrivateLinkage::buildPrivateLinkageArgs(TR::Node *callNode,
    int32_t argIndex = 0;
    int32_t numMemArgs = 0;
    int32_t memArgSize = 0;
+   int32_t firstExplicitArg = 0;
    int32_t from, to, step;
    int32_t argSize = -getOffsetToFirstParm();
    int32_t totalSize = 0;
@@ -909,6 +910,14 @@ int32_t J9::ARM64::PrivateLinkage::buildPrivateLinkageArgs(TR::Node *callNode,
       from += step;
       }
 
+   // C helpers have an implicit first argument (the VM thread) that we have to account for
+   if (linkage == TR_CHelper)
+      {
+      TR_ASSERT(numIntArgRegs > 0, "This code doesn't handle passing this implicit arg on the stack");
+      numIntegerArgs++;
+      totalSize += TR::Compiler->om.sizeofReferenceAddress();
+      }
+
    for (int32_t i = from; (rightToLeft && i >= to) || (!rightToLeft && i <= to); i += step)
       {
       child = callNode->getChild(i);
@@ -960,6 +969,19 @@ int32_t J9::ARM64::PrivateLinkage::buildPrivateLinkageArgs(TR::Node *callNode,
    numIntegerArgs = 0;
    numFloatArgs = 0;
 
+   // C helpers have an implicit first argument (the VM thread) that we have to account for
+   if (linkage == TR_CHelper)
+      {
+      TR_ASSERT(numIntArgRegs > 0, "This code doesn't handle passing this implicit arg on the stack");
+      TR::Register *vmThreadArgRegister = cg()->allocateRegister();
+      generateMovInstruction(cg(), callNode, vmThreadArgRegister, cg()->getMethodMetaDataRegister());
+      dependencies->addPreCondition(vmThreadArgRegister, properties.getIntegerArgumentRegister(numIntegerArgs));
+      if (resType.getDataType() == TR::NoType)
+         dependencies->addPostCondition(vmThreadArgRegister, properties.getIntegerArgumentRegister(numIntegerArgs));
+      numIntegerArgs++;
+      firstExplicitArg = 1;
+      }
+
    // Helper linkage preserves all argument registers except the return register
    // TODO: C helper linkage does not, this code needs to make sure argument registers are killed in post dependencies
    for (int32_t i = from; (rightToLeft && i >= to) || (!rightToLeft && i <= to); i += step)
@@ -1021,16 +1043,18 @@ int32_t J9::ARM64::PrivateLinkage::buildPrivateLinkageArgs(TR::Node *callNode,
                      generateMovInstruction(cg(), callNode, tempReg, argRegister);
                      argRegister = tempReg;
                      }
-                  if (numIntegerArgs == 0)
+                  if (numIntegerArgs == firstExplicitArg)
                      {
                      // the first integer argument
                      TR::Register *resultReg;
                      if (resType.isAddress())
                         resultReg = cg()->allocateCollectedReferenceRegister();
                      else
                         resultReg = cg()->allocateRegister();
-                     dependencies->addPreCondition(argRegister, TR::RealRegister::x0);
+                     dependencies->addPreCondition(argRegister, properties.getIntegerArgumentRegister(numIntegerArgs));
                      dependencies->addPostCondition(resultReg, TR::RealRegister::x0);
+                     if (firstExplicitArg == 1)
+                        dependencies->addPostCondition(argRegister, properties.getIntegerArgumentRegister(numIntegerArgs));
                      }
                   else
                      {