tccgen: update "Fix invalid load generated by gfunc_return()"

tccgen.c:
- new function incr_offset(int) to increment a lvalue
- use it in gv/vstore to load/store from/to two-word types
- use it to advance the pointer to struct fields
- use it to load/store structs passed in registers
- structs: always assume that reg-classes of registers are 2^n
- adjust stack space when regsize > sizeof the_struct

x86_64-gen.c:
- return regsize=16 for VT_QLONG/QFLOAT

i386-gen.c:
- pass structs of size(8) as two VT_INT rather than one VT_LLONG
  (both should work now)

fixes a82aff3
fixes fd6d218 (slightly)

Author: grischka

i386-gen.c

@@ -31,10 +31,10 @@
 #define RC_INT     0x0001 /* generic integer register */
 #define RC_FLOAT   0x0002 /* generic float register */
 #define RC_EAX     0x0004
-#define RC_ST0     0x0008 
+#define RC_EDX     0x0008
 #define RC_ECX     0x0010
-#define RC_EDX     0x0020
-#define RC_EBX     0x0040
+#define RC_EBX     0x0020
+#define RC_ST0     0x0040
 
 #define RC_IRET    RC_EAX /* function return: integer register */
 #define RC_IRE2    RC_EDX /* function return: second integer register */
@@ -380,22 +380,23 @@ static const uint8_t fastcallw_regs[2] = { TREG_ECX, TREG_EDX };
 ST_FUNC int gfunc_sret(CType *vt, int variadic, CType *ret, int *ret_align, int *regsize)
 {
 #if defined(TCC_TARGET_PE) || TARGETOS_FreeBSD || TARGETOS_OpenBSD
-    int size, align;
+    int size, align, nregs;
     *ret_align = 1; // Never have to re-align return values for x86
     *regsize = 4;
     size = type_size(vt, &align);
     if (size > 8 || (size & (size - 1)))
         return 0;
+    nregs = 1;
     if (size == 8)
-        ret->t = VT_LLONG;
+        ret->t = VT_INT, nregs = 2;
     else if (size == 4)
         ret->t = VT_INT;
     else if (size == 2)
         ret->t = VT_SHORT;
     else
         ret->t = VT_BYTE;
     ret->ref = NULL;
-    return 1;
+    return nregs;
 #else
     *ret_align = 1; // Never have to re-align return values for x86
     return 0;

tccgen.c

@@ -1687,14 +1687,22 @@ static void pop_local_syms(Sym *b, int keep)
     sym_pop(&local_stack, b, keep);
 }
 
-static void incr_bf_adr(int o)
+/* increment an lvalue pointer */
+static void incr_offset(int offset)
 {
-    vtop->type = char_pointer_type;
-    gaddrof();
-    vpushs(o);
+    int t = vtop->type.t;
+    gaddrof(); /* remove VT_LVAL */
+    vtop->type.t = VT_PTRDIFF_T; /* set scalar type */
+    vpushs(offset);
     gen_op('+');
-    vtop->type.t = VT_BYTE | VT_UNSIGNED;
     vtop->r |= VT_LVAL;
+    vtop->type.t = t;
+}
+
+static void incr_bf_adr(int o)
+{
+    vtop->type.t = VT_BYTE | VT_UNSIGNED;
+    incr_offset(o);
 }
 
 /* single-byte load mode for packed or otherwise unaligned bitfields */
@@ -1860,8 +1868,18 @@ ST_FUNC int gv(int rc)
         r2_ok = !rc2 || ((vtop->r2 < VT_CONST) && (reg_classes[vtop->r2] & rc2));
 
         if (!r_ok || !r2_ok) {
-            if (!r_ok)
-                r = get_reg(rc);
+
+            if (!r_ok) {
+                if (1 /* we can 'mov (r),r' in cases */
+                    && r < VT_CONST
+                    && (reg_classes[r] & rc)
+                    && !rc2
+                    )
+                    save_reg_upstack(r, 1);
+                else
+                    r = get_reg(rc);
+            }
+
             if (rc2) {
                 int load_type = (bt == VT_QFLOAT) ? VT_DOUBLE : VT_PTRDIFF_T;
                 int original_type = vtop->type.t;
@@ -1885,12 +1903,7 @@ ST_FUNC int gv(int rc)
                     vdup();
                     vtop[-1].r = r; /* save register value */
                     /* increment pointer to get second word */
-                    vtop->type.t = VT_PTRDIFF_T;
-                    gaddrof();
-                    vpushs(PTR_SIZE);
-                    gen_op('+');
-                    vtop->r |= VT_LVAL;
-                    vtop->type.t = load_type;
+                    incr_offset(PTR_SIZE);
                 } else {
                     /* move registers */
                     if (!r_ok)
@@ -3748,14 +3761,8 @@ ST_FUNC void vstore(void)
                 vtop[-1].type.t = load_type;
                 store(r, vtop - 1);
                 vswap();
-                /* convert to int to increment easily */
-                vtop->type.t = VT_PTRDIFF_T;
-                gaddrof();
-                vpushs(PTR_SIZE);
-                gen_op('+');
-                vtop->r |= VT_LVAL;
+                incr_offset(PTR_SIZE);
                 vswap();
-                vtop[-1].type.t = load_type;
                 /* XXX: it works because r2 is spilled last ! */
                 store(vtop->r2, vtop - 1);
             } else {
@@ -6003,7 +6010,6 @@ ST_FUNC void unary(void)
                 indir();
             qualifiers = vtop->type.t & (VT_CONSTANT | VT_VOLATILE);
             test_lvalue();
-            gaddrof();
             /* expect pointer on structure */
             if ((vtop->type.t & VT_BTYPE) != VT_STRUCT)
                 expect("struct or union");
@@ -6014,16 +6020,15 @@ ST_FUNC void unary(void)
                 expect("field name");
 	    s = find_field(&vtop->type, tok, &cumofs);
             /* add field offset to pointer */
-            vtop->type = char_pointer_type; /* change type to 'char *' */
-            vpushi(cumofs);
-            gen_op('+');
+            incr_offset(cumofs);
             /* change type to field type, and set to lvalue */
             vtop->type = s->type;
             vtop->type.t |= qualifiers;
             /* an array is never an lvalue */
-            if (!(vtop->type.t & VT_ARRAY)) {
-                vtop->r |= VT_LVAL;
+            if (vtop->type.t & VT_ARRAY) {
+                vtop->r &= ~VT_LVAL;
 #ifdef CONFIG_TCC_BCHECK
+            } else {
                 /* if bound checking, the referenced pointer must be checked */
                 if (tcc_state->do_bounds_check)
                     vtop->r |= VT_MUSTBOUND;
@@ -6128,10 +6133,20 @@ ST_FUNC void unary(void)
 #endif
             } else {
                 /* return value */
-                for (r = ret.r + ret_nregs + !ret_nregs; r-- > ret.r;) {
+                n = ret_nregs;
+                while (n > 1) {
+                    int rc = reg_classes[ret.r] & ~(RC_INT | RC_FLOAT);
+                    /* We assume that when a structure is returned in multiple
+                       registers, their classes are consecutive values of the
+                       suite s(n) = 2^n */
+                    rc <<= --n;
+                    for (r = 0; r < NB_REGS; ++r)
+                        if (reg_classes[r] & rc)
+                            break;
                     vsetc(&ret.type, r, &ret.c);
-                    vtop->r2 = ret.r2; /* Loop only happens when r2 is VT_CONST */
                 }
+                vsetc(&ret.type, ret.r, &ret.c);
+                vtop->r2 = ret.r2;
 
                 /* handle packed struct return */
                 if (((s->type.t & VT_BTYPE) == VT_STRUCT) && ret_nregs) {
@@ -6140,9 +6155,9 @@ ST_FUNC void unary(void)
                     size = type_size(&s->type, &align);
                     /* We're writing whole regs often, make sure there's enough
                        space.  Assume register size is power of 2.  */
-                    if (regsize > align)
-                      align = regsize;
-		    loc &= -align;
+                    size = (size + regsize - 1) & -regsize;
+                    if (ret_align > align)
+                        align = ret_align;
                     loc = (loc - size) & -align;
                     addr = loc;
                     offset = 0;
@@ -6619,11 +6634,12 @@ static void gfunc_return(CType *func_type)
             vstore();
         } else {
             /* returning structure packed into registers */
-            int size, addr, align, rc;
+            int size, addr, align, rc, n;
             size = type_size(func_type,&align);
-            if ((vtop->r != (VT_LOCAL | VT_LVAL) ||
-                 (vtop->c.i & (ret_align-1)))
-                && (align & (ret_align-1))) {
+            if ((align & (ret_align - 1))
+                && ((vtop->r & VT_VALMASK) < VT_CONST /* pointer to struct */
+                    || (vtop->c.i & (ret_align - 1))
+                    )) {
                 loc = (loc - size) & -ret_align;
                 addr = loc;
                 type = *func_type;
@@ -6635,22 +6651,19 @@ static void gfunc_return(CType *func_type)
             }
             vtop->type = ret_type;
             rc = RC_RET(ret_type.t);
-            if (ret_nregs == 1)
+            //printf("struct return: n:%d t:%02x rc:%02x\n", ret_nregs, ret_type.t, rc);
+            for (n = ret_nregs; --n > 0;) {
+                vdup();
                 gv(rc);
-            else {
-                for (;;) {
-                    vdup();
-                    gv(rc);
-                    vpop();
-                    if (--ret_nregs == 0)
-                      break;
-                    /* We assume that when a structure is returned in multiple
-                       registers, their classes are consecutive values of the
-                       suite s(n) = 2^n */
-                    rc <<= 1;
-                    vtop->c.i += regsize;
-                }
+                vswap();
+                incr_offset(regsize);
+                /* We assume that when a structure is returned in multiple
+                   registers, their classes are consecutive values of the
+                   suite s(n) = 2^n */
+                rc <<= 1;
             }
+            gv(rc);
+            vtop -= ret_nregs - 1;
         }
     } else {
         gv(RC_RET(func_type->t));

tests/tests2/131_return_struct_in_reg.c

@@ -1,49 +1,70 @@
 #include<stdio.h>
 
-#define DATA 0x1234567890abcdll, 0x5a5aa5a5f0f00f0fll
+struct s1 {
+    unsigned char a:4, b:4;
+} g1 = { 0x05, 0x0a };
 
-struct s {
-	long long int a;
-	long long int b;
-};
+struct s2 {
+    unsigned char a, b;
+} g2 = { 0x12, 0x34 };
 
-struct {
-	struct s d;
-} g = { { DATA } }, *gp = &g;
+struct s4 {
+    unsigned short a, b;
+} g4 = { 0x1245, 0x5678 };
 
-struct s
-foo1(void)
-{
-	struct s d = { DATA };
-	struct s *p = &d;
-	long long int x = 0;
-	return *p;
-}
+struct s8 {
+    unsigned a, b;
+} g8 = { 0x12345678, 0x9abcdef0 };
 
-struct s
-foo2(void)
-{
-	long long int unused = 0;
-	return gp->d;
-}
+/* returned in 2 registers on riscv64 */
+struct s16 {
+    unsigned long long a, b;
+} g16 = { 0x123456789abcdef0ULL, 0xfedcba9876543210ULL };
 
-struct s
-foo3(void)
-{
-	struct s d = { DATA };
-	long long int unused = 0;
-	return d;
+/* Homogeneous float aggregate on ARM hard-float */
+struct s_f4 {
+    double a, b, c, d;
+} g_f4 = { 1,2,3,4 };
+
+#define def(S) \
+struct s##S f##S(int x) \
+{ \
+    struct s##S l##S = g##S, *p##S = &l##S; \
+    if (x == 0) \
+        return g##S; \
+    else if (x == 1) \
+        return l##S; \
+    else \
+        return *p##S; \
 }
 
-int
-main(void)
+def(1)
+def(2)
+def(4)
+def(8)
+def(16)
+def(_f4)
+
+#define chk(S,x) \
+    struct s##S l##S = f##S(x); \
+    printf("%02llx %02llx\n", \
+        (unsigned long long)l##S.a, \
+        (unsigned long long)l##S.b \
+        );
+
+int main()
 {
-	struct s d;
-	d = foo1();
-	printf("%llx %llx\n", d.a, d.b);
-	d = foo2();
-	printf("%llx %llx\n", d.a, d.b);
-	d = foo3();
-	printf("%llx %llx\n", d.a, d.b);
-	return 0;
+    for (int x = 0;;) {
+        chk(1,x);
+        chk(2,x);
+        chk(4,x);
+        chk(8,x);
+        chk(16,x);
+        struct s_f4 l_f4 = f_f4(x);
+        printf("%.1f %.1f %.1f %.1f\n", l_f4.a, l_f4.b, l_f4.c, l_f4.d);
+        if (++x > 2)
+            break;
+        printf("\n");
+    }
+    return 0;
 }

tests/tests2/131_return_struct_in_reg.expect

@@ -1,3 +1,20 @@
-1234567890abcd 5a5aa5a5f0f00f0f
-1234567890abcd 5a5aa5a5f0f00f0f
-1234567890abcd 5a5aa5a5f0f00f0f
+05 0a
+12 34
+1245 5678
+12345678 9abcdef0
+123456789abcdef0 fedcba9876543210
+1.0 2.0 3.0 4.0
+
+05 0a
+12 34
+1245 5678
+12345678 9abcdef0
+123456789abcdef0 fedcba9876543210
+1.0 2.0 3.0 4.0
+
+05 0a
+12 34
+1245 5678
+12345678 9abcdef0
+123456789abcdef0 fedcba9876543210
+1.0 2.0 3.0 4.0

x86_64-gen.c

@@ -33,8 +33,8 @@
 #define RC_INT     0x0001 /* generic integer register */
 #define RC_FLOAT   0x0002 /* generic float register */
 #define RC_RAX     0x0004
-#define RC_RCX     0x0008
-#define RC_RDX     0x0010
+#define RC_RDX     0x0008
+#define RC_RCX     0x0010
 #define RC_RSI     0x0020
 #define RC_RDI     0x0040
 #define RC_ST0     0x0080 /* only for long double */
@@ -1223,9 +1223,11 @@ ST_FUNC int classify_x86_64_va_arg(CType *ty)
 ST_FUNC int gfunc_sret(CType *vt, int variadic, CType *ret, int *ret_align, int *regsize)
 {
     int size, align, reg_count;
+    if (classify_x86_64_arg(vt, ret, &size, &align, &reg_count) == x86_64_mode_memory)
+        return 0;
     *ret_align = 1; // Never have to re-align return values for x86-64
-    *regsize = 8;
-    return (classify_x86_64_arg(vt, ret, &size, &align, &reg_count) != x86_64_mode_memory);
+    *regsize = 8 * reg_count; /* the (virtual) regsize is 16 for VT_QLONG/QFLOAT */
+    return 1;
 }
 
 #define REGN 6