Fix invoke stack pointer clobbering

task1/CodegenImpl.java

@@ -148,24 +148,24 @@ public class CodegenImpl implements Codegen {
 		String methodLabel = String.format("%s_%d", call.name, argLen);
 		StringBuilder builder = new StringBuilder();
 
-		// Store return address & current stack pointer
-		builder.append("mv s7,sp\n");
+		// Store return address
 		builder.append("sw ra,-4(sp)\n");
-		builder.append("addi sp,sp,-4\n");
+		builder.append("mv t0,sp\n");
+		// shuffle stack pointer to start of arguments
+		builder.append(String.format("addi sp,sp,-%d\n", (argLen + 1) * 4));
+		builder.append("sw t0,-8(sp)\n"); // store old stack pointer (top of frame)
 
 		for (int i = argLen - 1; i >= 0; i--) {
 			Exp argExp = call.args.get(i);
 
 			builder.append(compileExp(argExp));
 			builder.append(
-				"sw a0,-4(sp)\n"
-				+ "addi sp,sp,-4\n"
+				String.format("sw a0,%d(sp)\n", i*4)
 			);
 		}
 
-		// push old frame pointer & start-of-frame pointer
+		// push old frame pointer
 		builder.append("sw fp,-4(sp)\n");
-		builder.append("sw s7,-8(sp)\n");
 		builder.append("addi sp,sp,-8\n");
 
 		builder.append(
@@ -175,6 +175,7 @@ public class CodegenImpl implements Codegen {
 			// restore old frame pointer & stack pointer
 			+ "lw fp,4(sp)\n"
 			+ "lw sp,(sp)\n"
+			// restore return address of caller
 			+ "lw ra,-4(sp)\n"
 		);
 

task2/CodegenImpl.java

@@ -148,24 +148,24 @@ public class CodegenImpl implements Codegen {
 		String methodLabel = String.format("%s_%d", call.name, argLen);
 		StringBuilder builder = new StringBuilder();
 
-		// Store return address & current stack pointer
-		builder.append("mv s7,sp\n");
+		// Store return address
 		builder.append("sw ra,-4(sp)\n");
-		builder.append("addi sp,sp,-4\n");
+		builder.append("mv t0,sp\n");
+		// shuffle stack pointer to start of arguments
+		builder.append(String.format("addi sp,sp,-%d\n", (argLen + 1) * 4));
+		builder.append("sw t0,-8(sp)\n"); // store old stack pointer (top of frame)
 
 		for (int i = argLen - 1; i >= 0; i--) {
 			Exp argExp = call.args.get(i);
 
 			builder.append(compileExp(argExp));
 			builder.append(
-				"sw a0,-4(sp)\n"
-				+ "addi sp,sp,-4\n"
+				String.format("sw a0,%d(sp)\n", i*4)
 			);
 		}
 
-		// push old frame pointer & start-of-frame pointer
+		// push old frame pointer
 		builder.append("sw fp,-4(sp)\n");
-		builder.append("sw s7,-8(sp)\n");
 		builder.append("addi sp,sp,-8\n");
 
 		builder.append(
@@ -175,6 +175,7 @@ public class CodegenImpl implements Codegen {
 			// restore old frame pointer & stack pointer
 			+ "lw fp,4(sp)\n"
 			+ "lw sp,(sp)\n"
+			// restore return address of caller
 			+ "lw ra,-4(sp)\n"
 		);
 

task3/CodegenImpl.java

@@ -148,24 +148,24 @@ public class CodegenImpl implements Codegen {
 		String methodLabel = String.format("%s_%d", call.name, argLen);
 		StringBuilder builder = new StringBuilder();
 
-		// Store return address & current stack pointer
-		builder.append("mv s7,sp\n");
+		// Store return address
 		builder.append("sw ra,-4(sp)\n");
-		builder.append("addi sp,sp,-4\n");
+		builder.append("mv t0,sp\n");
+		// shuffle stack pointer to start of arguments
+		builder.append(String.format("addi sp,sp,-%d\n", (argLen + 1) * 4));
+		builder.append("sw t0,-8(sp)\n"); // store old stack pointer (top of frame)
 
 		for (int i = argLen - 1; i >= 0; i--) {
 			Exp argExp = call.args.get(i);
 
 			builder.append(compileExp(argExp));
 			builder.append(
-				"sw a0,-4(sp)\n"
-				+ "addi sp,sp,-4\n"
+				String.format("sw a0,%d(sp)\n", i*4)
 			);
 		}
 
-		// push old frame pointer & start-of-frame pointer
+		// push old frame pointer
 		builder.append("sw fp,-4(sp)\n");
-		builder.append("sw s7,-8(sp)\n");
 		builder.append("addi sp,sp,-8\n");
 
 		builder.append(
@@ -175,6 +175,7 @@ public class CodegenImpl implements Codegen {
 			// restore old frame pointer & stack pointer
 			+ "lw fp,4(sp)\n"
 			+ "lw sp,(sp)\n"
+			// restore return address of caller
 			+ "lw ra,-4(sp)\n"
 		);