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Commit 7fcdf1c5 authored by Jack Palevich's avatar Jack Palevich
Browse files

Adjust stack alignment for local variables to work more like arguments. 

This makes it easier to generate frame-pointer-relative addresses for ARM.

Prior to this we had stored char sized local variables in the highest
address of the 4-byte stack allocation. Now we store "char"s in the
lowest address of the 4-byte stack allocation, just like chars are
passed as arguments.

We now store global chars on byte boundaries.
parent 894c5cd2

libacc/acc.cpp

+43 −7
Original line number Diff line number Diff line
@@ -481,14 +481,27 @@ class Compiler : public ErrorSink { 
        virtual size_t sizeOf(Type* type) = 0;



        /**

         * Stack argument size of this data type.

         * Stack alignment of this type of data

         */

        virtual size_t stackAlignmentOf(Type* pType) = 0;



        /**

         * Argument stack argument size of this data type.

         */

        virtual size_t stackSizeOf(Type* pType) = 0;



        virtual Type* getR0Type() {

        Type* getR0Type() {

            return mExpressionStack.back().pType;

        }



        ExpressionType getR0ExpressionType() {

            return mExpressionStack.back().et;

        }



        void setR0ExpressionType(ExpressionType et) {

            mExpressionStack.back().et = et;

        }



    protected:

        /*

         * Output a byte. Handles all values, 0..ff.
@@ -1450,6 +1463,8 @@ class Compiler : public ErrorSink { 
         */

        virtual size_t alignmentOf(Type* pType){

            switch(pType->tag) {

                case TY_CHAR:

                    return 1;

                case TY_DOUBLE:

                    return 8;

                default:
@@ -1477,6 +1492,15 @@ class Compiler : public ErrorSink { 
            }

        }



        virtual size_t stackAlignmentOf(Type* pType) {

            switch(pType->tag) {

                case TY_DOUBLE:

                    return 8;

                default:

                    return 4;

            }

        }



        virtual size_t stackSizeOf(Type* pType) {

            switch(pType->tag) {

                case TY_DOUBLE:
@@ -2381,8 +2405,13 @@ class Compiler : public ErrorSink { 
         * Alignment (in bytes) for this type of data

         */

        virtual size_t alignmentOf(Type* pType){

            switch (pType->tag) {

            case TY_CHAR:

                return 1;

            default:

                return 4;

            }

        }



        /**

         * Array element alignment (in bytes) for this type of data.
@@ -2404,6 +2433,10 @@ class Compiler : public ErrorSink { 
            }

        }



        virtual size_t stackAlignmentOf(Type* pType){

            return 4;

        }



        virtual size_t stackSizeOf(Type* pType) {

            switch(pType->tag) {

                case TY_DOUBLE:
@@ -4538,9 +4571,12 @@ class Compiler : public ErrorSink { 
                }

                int variableAddress = 0;

                addLocalSymbol(pDecl);

                size_t alignment = pGen->alignmentOf(pDecl);

                loc = (loc + alignment - 1) & ~ (alignment-1);

                loc = loc + pGen->sizeOf(pDecl);

                size_t alignment = pGen->stackAlignmentOf(pDecl);

                size_t alignmentMask = ~ (alignment - 1);

                size_t sizeOf = pGen->sizeOf(pDecl);

                loc = (loc + alignment - 1) & alignmentMask;

                size_t alignedSize = (sizeOf + alignment - 1) & alignmentMask;

                loc = loc + alignedSize;

                variableAddress = -loc;

                VI(pDecl->id)->pAddress = (void*) variableAddress;

                if (accept('=')) {
@@ -4674,7 +4710,7 @@ class Compiler : public ErrorSink { 
                        Type* pArg = pP->pHead;

                        addLocalSymbol(pArg);

                        /* read param name and compute offset */

                        size_t alignment = pGen->alignmentOf(pArg);

                        size_t alignment = pGen->stackAlignmentOf(pArg);

                        a = (a + alignment - 1) & ~ (alignment-1);

                        VI(pArg->id)->pAddress = (void*) a;

                        a = a + pGen->stackSizeOf(pArg);