[flang] [llvm] [clang] [compiler-rt] [clang-tools-extra] [clang] Add support for new loop attribute [[clang::code_align()]] (PR #70762)

[Erich Keane via llvm-commits]

================
@@ -0,0 +1,126 @@
+// RUN: %clang_cc1 -fsyntax-only -verify=expected,c-local -x c %s
+// RUN: %clang_cc1 -fsyntax-only -verify=expected,cpp-local -pedantic -x c++ -std=c++11 %s
+
+void foo() {
+  int i;
+  int a[10], b[10];
+
+  [[clang::code_align(8)]]
+  for (i = 0; i < 10; ++i) {  // this is OK
+    a[i] = b[i] = 0;
+  }
+  // expected-error at +1{{'code_align' attribute only applies to 'for', 'while', and 'do' statements}}
+  [[clang::code_align(4)]]
+  i = 7;
+  for (i = 0; i < 10; ++i) {
+    a[i] = b[i] = 0;
+  }
+
+  // expected-error at +1{{'code_align' attribute cannot be applied to a declaration}}
+  [[clang::code_align(12)]] int n[10];
+}
+
+void bar(int);
+// cpp-local-note at +1{{declared here}}
+void foo1(int A)
+{
+  // expected-error at +1{{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was 0}}
+  [[clang::code_align(0)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-error at +1{{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was -4}}
+  [[clang::code_align(-4)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+    // cpp-local-error at +2{{integral constant expression must have integral or unscoped enumeration type, not 'double'}}
+    // c-local-error at +1{{integer constant expression must have integer type, not 'double'}}
+  [[clang::code_align(64.0)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-error at +1{{'code_align' attribute takes one argument}}
+  [[clang::code_align()]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-error at +1{{'code_align' attribute takes one argument}}
+  [[clang::code_align(4,8)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // no diagnostic is expected
+  [[clang::code_align(32)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // cpp-local-error at +2{{integral constant expression must have integral or unscoped enumeration type, not 'const char[4]'}}
+  // c-local-error at +1{{integer constant expression must have integer type, not 'char[4]'}}
+  [[clang::code_align("abc")]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  [[clang::code_align(64)]] // expected-note{{previous attribute is here}}
+  [[clang::code_align(64)]] // expected-error{{duplicate loop attribute 'code_align'}}
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-error at +1{{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was 7}}
+  [[clang::code_align(7)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-error at +1{{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was 5000}}
+  [[clang::code_align(5000)]]
+  for(int I=0; I<128; ++I) { bar(I); }
+
+  // expected-warning at +2 {{integer literal is too large to be represented in a signed integer type, interpreting as unsigned}}
+  // expected-error at +1 {{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was 9223372036854775808}}
+  [[clang::code_align(9223372036854775808)]]
+  for(int I=0; I<256; ++I) { bar(I); }
+
+  // expected-error at +1 {{'code_align' attribute requires an integer argument which is a constant power of two between 1 and 4096 inclusive; provided argument was 0}}
----------------
erichkeane wrote:

Right, that is more or less what I was saying before, if you're converting an `APInt` that is too large for conversion operators, you'll end up getting the wrong answer or asserting, etc.  So you have to manage how that comes out better.

https://github.com/llvm/llvm-project/pull/70762