Optimise negative offsets: don't subtract until necessary

1 files changed, 38 insertions, 9 deletions

diff --git a/cgopt.c b/cgopt.c
index 977a543..4dc9225 100644
--- a/cgopt.c
+++ b/cgopt.c
@@ -705,7 +705,12 @@ static void optimize_b_stack_access2 (struct instruction *instruction)
 }
 #	endif
 
-static void compute_extreme_stack_offsets (register int b_offset,int *min_a_offset)
+static void compute_extreme_stack_offsets (register int b_offset
+#ifdef THUMB2
+		,int *min_a_offset
+		,struct instruction **first_to_fix_a_offset
+#endif
+		)
 {
 	struct instruction *instruction;
 	
@@ -759,12 +764,16 @@ static void compute_extreme_stack_offsets (register int b_offset,int *min_a_offs
 					if (instruction->instruction_parameters[0].parameter_offset<b_offset)
 						b_offset=instruction->instruction_parameters[0].parameter_offset;
 				}
+#ifdef THUMB2
 				else if (instruction->instruction_parameters[0].parameter_type==P_INDIRECT
 					&& instruction->instruction_parameters[0].parameter_data.reg.r==A_STACK_POINTER)
 				{
 					if (instruction->instruction_parameters[0].parameter_offset<*min_a_offset)
 						*min_a_offset=instruction->instruction_parameters[0].parameter_offset;
+					if (instruction->instruction_parameters[0].parameter_offset<-255)
+						*first_to_fix_a_offset = instruction;
 				}
+#endif
 				break;
 			case 2:
 				if (instruction->instruction_parameters[0].parameter_type==P_INDIRECT
@@ -774,12 +783,16 @@ static void compute_extreme_stack_offsets (register int b_offset,int *min_a_offs
 					if (instruction->instruction_parameters[0].parameter_offset<b_offset)
 						b_offset=instruction->instruction_parameters[0].parameter_offset;
 				}
+#ifdef THUMB2
 				else if (instruction->instruction_parameters[0].parameter_type==P_INDIRECT
 					&& instruction->instruction_parameters[0].parameter_data.reg.r==A_STACK_POINTER)
 				{
 					if (instruction->instruction_parameters[0].parameter_offset<*min_a_offset)
 						*min_a_offset=instruction->instruction_parameters[0].parameter_offset;
+					if (instruction->instruction_parameters[0].parameter_offset<-255)
+						*first_to_fix_a_offset = instruction;
 				}
+#endif
 				if (instruction->instruction_parameters[1].parameter_type==P_INDIRECT
 					&& instruction->instruction_parameters[1].parameter_data.reg.r==B_STACK_POINTER)
 				{
@@ -787,12 +800,16 @@ static void compute_extreme_stack_offsets (register int b_offset,int *min_a_offs
 					if (instruction->instruction_parameters[1].parameter_offset<b_offset)
 						b_offset=instruction->instruction_parameters[1].parameter_offset;
 				}
+#ifdef THUMB2
 				else if (instruction->instruction_parameters[1].parameter_type==P_INDIRECT
 					&& instruction->instruction_parameters[1].parameter_data.reg.r==A_STACK_POINTER)
 				{
 					if (instruction->instruction_parameters[1].parameter_offset<*min_a_offset)
 						*min_a_offset=instruction->instruction_parameters[1].parameter_offset;
+					if (instruction->instruction_parameters[1].parameter_offset<-255)
+						*first_to_fix_a_offset = instruction;
 				}
+#endif
 		}
 	}
 }
@@ -823,7 +840,6 @@ void optimize_stack_access (struct basic_block *block,int *a_offset_p,int *b_off
 	)
 {
 	struct instruction *instruction;
-	int min_a_offset=0;
 
 # ifdef M68000	
 	a_offset=0;
@@ -836,17 +852,27 @@ void optimize_stack_access (struct basic_block *block,int *a_offset_p,int *b_off
 	previous_a_stack_parameter=NULL;
 	previous_b_stack_parameter=NULL;
 # endif
+# ifdef THUMB2
+	int min_a_offset=0;
+	struct instruction *first_instruction_to_fix_a_offset=NULL;
+# endif
 
 	b_offset=0;
 
-	compute_extreme_stack_offsets (b_offset_p, &min_a_offset);
+	compute_extreme_stack_offsets (b_offset_p
+# ifdef THUMB2
+			, &min_a_offset
+			, &first_instruction_to_fix_a_offset
+# endif
+			);
 
 # ifdef THUMB2
-	int fix_a_offset = 0;
+	int fix_a_offset=0;
+	int found_first_to_fix_a_offset=0;
 	if (min_a_offset <= -256)
 	{
 		fix_a_offset=-min_a_offset;
-		insert_decrement_a_stack_pointer (block->block_instructions,fix_a_offset);
+		insert_decrement_a_stack_pointer (first_instruction_to_fix_a_offset,fix_a_offset);
 		*a_offset_p+=fix_a_offset;
 	}
 # endif
@@ -935,10 +961,13 @@ void optimize_stack_access (struct basic_block *block,int *a_offset_p,int *b_off
 		if (instruction->instruction_icode==IMOVE){
 # ifdef ARM
 #  ifdef THUMB2
-			if (instruction->instruction_parameters[1].parameter_data.reg.r==A_STACK_POINTER)
-				instruction->instruction_parameters[1].parameter_offset+=fix_a_offset;
-			if (instruction->instruction_parameters[0].parameter_data.reg.r==A_STACK_POINTER)
-				instruction->instruction_parameters[0].parameter_offset+=fix_a_offset;
+			if (found_first_to_fix_a_offset || instruction==first_instruction_to_fix_a_offset) {
+				if (instruction->instruction_parameters[1].parameter_data.reg.r==A_STACK_POINTER)
+					instruction->instruction_parameters[1].parameter_offset+=fix_a_offset;
+				if (instruction->instruction_parameters[0].parameter_data.reg.r==A_STACK_POINTER)
+					instruction->instruction_parameters[0].parameter_offset+=fix_a_offset;
+				found_first_to_fix_a_offset=1;
+			}
 #  endif
 			if (instruction->instruction_parameters[1].parameter_type==P_INDIRECT &&
 				instruction->instruction_parameters[1].parameter_data.reg.r==A_STACK_POINTER)