[clang][AVR] Improve compatibility of inline assembly with avr-gcc

[benshi001]

Allow the value 64 to be round up to 0 for constraint 'I'.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Ben Shi (benshi001)

Changes

Allow the value 64 to be round up to 0 for constraint 'I'.

---

Full diff: https://github.com/llvm/llvm-project/pull/136534.diff

3 Files Affected:

• (modified) clang/lib/Basic/Targets/AVR.h (+1-1)
• (modified) clang/test/CodeGen/avr/avr-inline-asm-constraints.c (+2)
• (modified) clang/test/CodeGen/avr/avr-unsupported-inline-asm-constraints.c (+1)

diff --git a/clang/lib/Basic/Targets/AVR.h b/clang/lib/Basic/Targets/AVR.h
index 2117ab58e6f30..b2f2711c35435 100644
--- a/clang/lib/Basic/Targets/AVR.h
+++ b/clang/lib/Basic/Targets/AVR.h
@@ -124,7 +124,7 @@ class LLVM_LIBRARY_VISIBILITY AVRTargetInfo : public TargetInfo {
       Info.setAllowsRegister();
       return true;
     case 'I': // 6-bit positive integer constant
-      Info.setRequiresImmediate(0, 63);
+      Info.setRequiresImmediate(0, 64);
       return true;
     case 'J': // 6-bit negative integer constant
       Info.setRequiresImmediate(-63, 0);
diff --git a/clang/test/CodeGen/avr/avr-inline-asm-constraints.c b/clang/test/CodeGen/avr/avr-inline-asm-constraints.c
index 3a956de8db48f..c8d83b4848312 100644
--- a/clang/test/CodeGen/avr/avr-inline-asm-constraints.c
+++ b/clang/test/CodeGen/avr/avr-inline-asm-constraints.c
@@ -71,6 +71,8 @@ void z() {
 void I() {
   // CHECK: call addrspace(0) void asm sideeffect "subi r30, $0", "I"(i16 50)
   asm("subi r30, %0" :: "I"(50));
+  // CHECK: call addrspace(0) void asm sideeffect "subi r30, $0", "I"(i16 64)
+  asm("subi r30, %0" :: "I"(64));
 }
 
 void J() {
diff --git a/clang/test/CodeGen/avr/avr-unsupported-inline-asm-constraints.c b/clang/test/CodeGen/avr/avr-unsupported-inline-asm-constraints.c
index 29f0b69285fa8..52b8d1cb044ca 100644
--- a/clang/test/CodeGen/avr/avr-unsupported-inline-asm-constraints.c
+++ b/clang/test/CodeGen/avr/avr-unsupported-inline-asm-constraints.c
@@ -6,4 +6,5 @@ int foo(void) {
   __asm__ volatile("foo %0, 1" : : "fo" (val)); // expected-error {{invalid input constraint 'fo' in asm}}
   __asm__ volatile("foo %0, 1" : : "Nd" (val)); // expected-error {{invalid input constraint 'Nd' in asm}}
   __asm__ volatile("subi r30, %0" : : "G" (1)); // expected-error {{value '1' out of range for constraint 'G'}}
+  __asm__ volatile("out %0, r20" : : "I" (65)); // expected-error {{value '65' out of range for constraint 'I'}}
 }

[s-barannikov]

gcc doesn't seem to allow it?
https://godbolt.org/z/4zh8TTPac

[benshi001]

gcc doesn't seem to allow it? https://godbolt.org/z/4zh8TTPac

avr-gcc allow value 64 for constraint 'I' in very special case, such as #51513.

And my solution is loosen that check in the frontend, but let the AVR backend to deny the illegal constraint value 64.

[s-barannikov]

gcc doesn't seem to allow it? https://godbolt.org/z/4zh8TTPac

avr-gcc allow value 64 for constraint 'I' in very special case, such as #51513.

I guess the test needs to be updated to be representative?

And my solution is loosen that check in the frontend, but let the AVR backend to deny the illegal constraint value 64.

This deserves a comment in code so that other people don't get confused about this and don't try to change it back to 63.

[benshi001]

gcc doesn't seem to allow it? https://godbolt.org/z/4zh8TTPac

avr-gcc allow value 64 for constraint 'I' in very special case, such as #51513.

I guess the test needs to be updated to be representative?

And my solution is loosen that check in the frontend, but let the AVR backend to deny the illegal constraint value 64.

This deserves a comment in code so that other people don't get confused about this and don't try to change it back to 63.

Thanks.

1. Comment lines are supplemented.
2. A reject test in the backend is added.

[s-barannikov]

Thanks, LGTM