JIT: Rewrite initial parameter frame layout in terms of new ABI info (dotnet#101340)

Rewrite `lvaAssignVirtualFrameOffsetsToArgs` to make use of the ABI
information that was already computed as part of ABI classification in
the frontend.

Author: jakobbotsch

src/coreclr/jit/abi.cpp

@@ -71,14 +71,15 @@ regMaskTP ABIPassingSegment::GetRegisterMask() const
 //   Offset relative to the first stack argument.
 //
 // Remarks:
-//   On x86, where arguments are pushed in order and thus come in reverse order
-//   in the callee, this is the offset to subtract from the top of the stack to
-//   get the argument's address. By top of the stack is meant esp on entry + 4
-//   for the return address + total size of stack arguments. In varargs methods
-//   the varargs cookie contains the information required to allow the
-//   computation of the total size of stack arguments.
-//
-//   Outside x86 this is the offset to add to the first argument's address.
+//   On x86, for the managed ABI where arguments are pushed in order and thus
+//   come in reverse order in the callee, this is the offset to subtract from
+//   the top of the stack to get the argument's address. By top of the stack is
+//   meant esp on entry + 4 for the return address + total size of stack
+//   arguments. In varargs methods the varargs cookie contains the information
+//   required to allow the computation of the total size of stack arguments.
+//
+//   Outside the managed x86 ABI this is the offset to add to the first
+//   argument's address.
 //
 unsigned ABIPassingSegment::GetStackOffset() const
 {

src/coreclr/jit/abi.h

@@ -106,12 +106,18 @@ struct ClassifierInfo
 
 class X86Classifier
 {
-    RegisterQueue m_regs;
-    unsigned      m_stackArgSize = 0;
+    const ClassifierInfo& m_info;
+    RegisterQueue         m_regs;
+    unsigned              m_stackArgSize = 0;
 
 public:
     X86Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -122,11 +128,16 @@ class WinX64Classifier
 {
     RegisterQueue m_intRegs;
     RegisterQueue m_floatRegs;
-    unsigned      m_stackArgSize = 0;
+    unsigned      m_stackArgSize = 32;
 
 public:
     WinX64Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -142,6 +153,11 @@ class SysVX64Classifier
 public:
     SysVX64Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -158,6 +174,11 @@ class Arm64Classifier
 public:
     Arm64Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return roundUp(m_stackArgSize, TARGET_POINTER_SIZE);
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -182,6 +203,11 @@ class Arm32Classifier
 public:
     Arm32Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -198,6 +224,11 @@ class RiscV64Classifier
 public:
     RiscV64Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -214,6 +245,11 @@ class LoongArch64Classifier
 public:
     LoongArch64Classifier(const ClassifierInfo& info);
 
+    unsigned StackSize()
+    {
+        return m_stackArgSize;
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,
@@ -247,6 +283,11 @@ class SwiftABIClassifier
     {
     }
 
+    unsigned StackSize()
+    {
+        return m_classifier.StackSize();
+    }
+
     ABIPassingInformation Classify(Compiler*    comp,
                                    var_types    type,
                                    ClassLayout* structLayout,

src/coreclr/jit/compiler.h

@@ -3792,6 +3792,7 @@ class Compiler
     unsigned   lvaTableCnt; // lvaTable size (>= lvaCount)
 
     ABIPassingInformation* lvaParameterPassingInfo;
+    unsigned lvaParameterStackSize;
 
     unsigned lvaTrackedCount;             // actual # of locals being tracked
     unsigned lvaTrackedCountInSizeTUnits; // min # of size_t's sufficient to hold a bit for all the locals being tracked
@@ -3939,11 +3940,7 @@ class Compiler
     void lvaUpdateArgWithInitialReg(LclVarDsc* varDsc);
     void lvaUpdateArgsWithInitialReg();
     void lvaAssignVirtualFrameOffsetsToArgs();
-#ifdef UNIX_AMD64_ABI
-    int lvaAssignVirtualFrameOffsetToArg(unsigned lclNum, unsigned argSize, int argOffs, int* callerArgOffset);
-#else  // !UNIX_AMD64_ABI
-    int lvaAssignVirtualFrameOffsetToArg(unsigned lclNum, unsigned argSize, int argOffs);
-#endif // !UNIX_AMD64_ABI
+    bool lvaGetRelativeOffsetToCallerAllocatedSpaceForParameter(unsigned lclNum, int* offset);
     void lvaAssignVirtualFrameOffsetsToLocals();
     bool lvaParamHasLocalStackSpace(unsigned lclNum);
     int lvaAllocLocalAndSetVirtualOffset(unsigned lclNum, unsigned size, int stkOffs);