[clang] Fix wrong ABI on AVRTiny

[benshi001]

Summary

A scalar which exceeds 4 bytes should be returned
via a stack slot, on AVRTiny.

[benshi001]

clang/test/CodeGen/avr/return-value.c

37

This file should be renamed to return.c instead of current struct.c, I will do that in another patch, just let you see clearly what I have changed.

[aykevl]

clang/test/CodeGen/avr/return-value.c

37

You can do that in the same patch. Phabricator should detect the renamed file and display it just like it does now.

[benshi001]

clang/test/CodeGen/avr/return-value.c

37

thanks.

clang/lib/CodeGen/TargetInfo.cpp

private:
   // AVR, or 4 on AVRTiny.
   const unsigned RetRegs;
 
 public:
   AVRABIInfo(CodeGenTypes &CGT, unsigned NPR, unsigned NRR)
       : DefaultABIInfo(CGT), ParamRegs(NPR), RetRegs(NRR) {}
 
   ABIArgInfo classifyReturnType(QualType Ty, bool &LargeRet) const {
-    if (isAggregateTypeForABI(Ty)) {
-      // On AVR, a return struct with size less than or equals to 8 bytes is
-      // returned directly via registers R18-R25. On AVRTiny, a return struct
-      // with size less than or equals to 4 bytes is returned directly via
-      // registers R22-R25.
-      if (getContext().getTypeSize(Ty) <= RetRegs * 8)
-        return ABIArgInfo::getDirect();
-      // A return struct with larger size is returned via a stack
-      // slot, along with a pointer to it as the function's implicit argument.
+    if (isAggregateTypeForABI(Ty) &&
+        getContext().getTypeSize(Ty) <= RetRegs * 8)
+    // A return value (struct or scalar) with larger size is returned via a
+    // stack slot, along with a pointer as the function's implicit argument.
+    if (getContext().getTypeSize(Ty) > RetRegs * 8) {
       LargeRet = true;
       return getNaturalAlignIndirect(Ty);
     }
     // Otherwise we follow the default way which is compatible.
     return DefaultABIInfo::classifyReturnType(Ty);
   }
 
   ABIArgInfo classifyArgumentType(QualType Ty, unsigned &NumRegs) const {

clang/test/CodeGen/avr/return-value.c

struct s06 foo06(int a, int b, int c) {
   return a0;
 }
 
 struct s04 foo04(int a, int b) {
   struct s04 a0;
   return a0;
 }
 
+long long fooi64(void) {
+  return 0xaa5533;
+}
+
 // AVR: %struct.s10 = type { i16, i16, i16, i16, i16 }
 // AVR: %struct.s06 = type { i16, i16, i16 }
 // AVR: %struct.s04 = type { i16, i16 }
 // AVR: define{{.*}} void @foo10(ptr {{.*}}, i16 noundef %a, i16 noundef %b, i16 noundef %c)
 // AVR: define{{.*}} %struct.s06 @foo06(i16 noundef %a, i16 noundef %b, i16 noundef %c)
 // AVR: define{{.*}} %struct.s04 @foo04(i16 noundef %a, i16 noundef %b)
+// AVR: define{{.*}} i64 @fooi64()
 
 // TINY: %struct.s10 = type { i16, i16, i16, i16, i16 }
 // TINY: %struct.s06 = type { i16, i16, i16 }
 // TINY: %struct.s04 = type { i16, i16 }
 // TINY: define{{.*}} void @foo10(ptr {{.*}}, i16 noundef %a, i16 noundef %b, i16 noundef %c)
 // TINY: define{{.*}} void @foo06(ptr {{.*}}, i16 noundef %a, i16 noundef %b, i16 noundef %c)
 // TINY: define{{.*}} %struct.s04 @foo04(i16 noundef %a, i16 noundef %b)
+// TINY: define{{.*}} void @fooi64(ptr {{.*}})