- Only move unaligned stack usage worth of parameters.

This is a simple optimization.

- When moving parameters for tailcall, and having pushed ip,
and adjusting the offset to account for that, split the adjustment
between sp and frame pointer, as frame pointer may or may not be sp.
This fixes mono#11489.

mono/mini/mini-arm.c

@@ -1624,10 +1624,10 @@ get_call_info (MonoMemPool *mp, MonoMethodSignature *sig)
 		add_general (&gr, &stack_size, &cinfo->sig_cookie, TRUE);
 	}
 
+	// Alignment causes tailcall to copy extra data unnecessarily.
 	DEBUG (g_print ("      stack size: %d (%d)\n", (stack_size + 15) & ~15, stack_size));
-	stack_size = ALIGN_TO (stack_size, MONO_ARCH_FRAME_ALIGNMENT);
-
-	cinfo->stack_usage = stack_size;
+	cinfo->unaligned_stack_usage = stack_size;
+	cinfo->stack_usage = ALIGN_TO (stack_size, MONO_ARCH_FRAME_ALIGNMENT);
 	return cinfo;
 }
 
@@ -2652,6 +2652,7 @@ mono_arch_emit_call (MonoCompile *cfg, MonoCallInst *call)
 
 	call->call_info = cinfo;
 	call->stack_usage = cinfo->stack_usage;
+	call->unaligned_stack_usage = cinfo->unaligned_stack_usage;
 }
 
 static void
@@ -5001,7 +5002,7 @@ mono_arch_output_basic_block (MonoCompile *cfg, MonoBasicBlock *bb)
 			gboolean const tailcall_reg = ins->opcode == OP_TAILCALL_REG;
 			MonoCallInst *call = (MonoCallInst*)ins;
 
-			max_len += call->stack_usage / sizeof (target_mgreg_t) * ins_get_size (OP_TAILCALL_PARAMETER);
+			max_len += call->unaligned_stack_usage / sizeof (target_mgreg_t) * ins_get_size (OP_TAILCALL_PARAMETER);
 
 			if (IS_HARD_FLOAT)
 				code = emit_float_args (cfg, call, code, &max_len, &offset);
@@ -5035,13 +5036,15 @@ mono_arch_output_basic_block (MonoCompile *cfg, MonoBasicBlock *bb)
 			 * Need to copy the arguments from the callee argument area to
 			 * the caller argument area, and pop the frame.
 			 */
-			if (call->stack_usage) {
+
+			if (call->unaligned_stack_usage) {
 				int i, prev_sp_offset = 0;
-				int saved_ip_offset = 0;
+				int saved_ip_offset_sp = 0;
+				int saved_ip_offset_fp = 0;
 
 				if (tailcall_membase || tailcall_reg) {
 					ARM_PUSH (code, 1 << ARMREG_IP);
-					saved_ip_offset = 4;
+					saved_ip_offset_sp = 4;
 				}
 
 				/* Compute size of saved registers restored below */
@@ -5055,16 +5058,18 @@ mono_arch_output_basic_block (MonoCompile *cfg, MonoBasicBlock *bb)
 				}
 
 				code = emit_big_add (code, ARMREG_IP, cfg->frame_reg, cfg->stack_usage + prev_sp_offset);
+				if (cfg->frame_reg == ARMREG_SP)
+					saved_ip_offset_fp = saved_ip_offset_sp;
 
 				/* Copy arguments on the stack to our argument area */
 				// FIXME a fixed size memcpy is desirable here,
 				// at least for larger values of stack_usage.
-				for (i = 0; i < call->stack_usage; i += sizeof (target_mgreg_t)) {
-					ARM_LDR_IMM (code, ARMREG_LR, ARMREG_SP, i + saved_ip_offset);
-					ARM_STR_IMM (code, ARMREG_LR, ARMREG_IP, i + saved_ip_offset);
+				for (i = 0; i < call->unaligned_stack_usage; i += sizeof (target_mgreg_t)) {
+					ARM_LDR_IMM (code, ARMREG_LR, ARMREG_SP, i + saved_ip_offset_sp);
+					ARM_STR_IMM (code, ARMREG_LR, ARMREG_IP, i + saved_ip_offset_fp);
 				}
 
-				if (saved_ip_offset)
+				if (saved_ip_offset_sp)
 					ARM_POP (code, 1 << ARMREG_IP);
 			}
 

mono/mini/mini-arm.h

@@ -215,6 +215,7 @@ typedef struct {
 
 struct CallInfo {
 	int nargs;
+	guint32 unaligned_stack_usage;
 	guint32 stack_usage;
 	/* The index of the vret arg in the argument list for RegTypeStructByAddr */
 	int vret_arg_index;

mono/mini/mini.h

@@ -740,6 +740,7 @@ struct MonoCallInst {
 	MonoInst *out_args;
 	MonoInst *vret_var;
 	gconstpointer fptr;
+	guint unaligned_stack_usage;
 	guint stack_usage;
 	guint stack_align_amount;
 	guint is_virtual : 1;