[win][arm64ec] Fix duplicate errors with the dontcall attribute

[dpaoliello]

Since the dontcall-* attributes are checked both by FastISel/GlobalISel and SelectionDAGBuilder, and both FastISel and GlobalISel bail for calls on Arm64EC for AFTER doing the check, we ended up emitting duplicate copies of this error.

This change moves the checking for dontcall-* in FastISel and GlobalISel to after it has been successfully lowered.

[llvmbot]

@llvm/pr-subscribers-backend-x86
@llvm/pr-subscribers-llvm-globalisel
@llvm/pr-subscribers-llvm-selectiondag

@llvm/pr-subscribers-backend-aarch64

Author: Daniel Paoliello (dpaoliello)

Changes

Since the dontcall-* attributes are checked both by FastISel and SelectionDAGBuilder, and FastISel bails for calls on Arm64EC for AFTER doing the check, we ended up emitting duplicate copies of this error.

This change moves the checking for dontcall-* in FastISel to after it has been successfully lowered.

---

Full diff: https://github.com/llvm/llvm-project/pull/152810.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/SelectionDAG/FastISel.cpp (+5-3)
• (added) llvm/test/CodeGen/AArch64/arm64ec-dont-call.ll (+21)

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index fb9eff942a464..5bc158a660080 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1148,9 +1148,11 @@ bool FastISel::lowerCall(const CallInst *CI) {
   CLI.setCallee(RetTy, FuncTy, CI->getCalledOperand(), std::move(Args), *CI)
       .setTailCall(IsTailCall);
 
-  diagnoseDontCall(*CI);
-
-  return lowerCallTo(CLI);
+  if (lowerCallTo(CLI)) {
+    diagnoseDontCall(*CI);
+    return true;
+  } else
+    return false;
 }
 
 bool FastISel::selectCall(const User *I) {
diff --git a/llvm/test/CodeGen/AArch64/arm64ec-dont-call.ll b/llvm/test/CodeGen/AArch64/arm64ec-dont-call.ll
new file mode 100644
index 0000000000000..febb8997f3e37
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/arm64ec-dont-call.ll
@@ -0,0 +1,21 @@
+; RUN: not llc -mtriple arm64ec-windows-msvc -o - %s 2>&1 | FileCheck %s
+
+define void @baz() #0 {
+  call void @foo()
+  ret void
+}
+
+define void @foo() #1 {
+  ret void
+}
+
+attributes #0 = { noinline optnone }
+attributes #1 = { "dontcall-error"="oh no foo" }
+
+; Regression test for `dontcall-error` for Arm64EC. Since this attribute is
+; checked both by FastISel and SelectionDAGBuilder, and FastISel was bailing for
+; Arm64EC AFTER doing the check, we ended up with duplicate copies of this
+; error.
+
+; CHECK: error: call to #foo marked "dontcall-error": oh no foo
+; CHECK-NOT: error:

[arsenm]

Suggested change

	; RUN: not llc -mtriple arm64ec-windows-msvc -o - %s 2>&1 | FileCheck %s
	; RUN: not llc -mtriple=arm64ec-windows-msvc -filetype=null %s 2>&1 | FileCheck %s

[arsenm]

Suggested change

	} else
	return false;
	}
	return false;

No else after return

[arsenm]

Suggested change

	bool Result = translateCallBase(CI, MIRBuilder);
	if (Result) {
	if (translateCallBase(CI, MIRBuilder)) {

[dpaoliello]

Possible build break: https://lab.llvm.org/buildbot/#/builders/154/builds/20134

FAIL: Clang :: Frontend/backend-attribute-error-warning.c (7019 of 88313)
******************** TEST 'Clang :: Frontend/backend-attribute-error-warning.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/22/include -nostdsysteminc -verify=expected,enabled -emit-codegen-only /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c # RUN: at line 1
+ /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/lib/clang/22/include -nostdsysteminc -verify=expected,enabled -emit-codegen-only /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c
error: diagnostics with 'error' severity expected but not seen: 
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 25 'expected-error': call to 'foo' declared with 'error' attribute: oh no foo
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 27 'expected-error': call to 'bar' declared with 'error' attribute: oh no bar
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 30 'expected-error': call to '__compiletime_assert_455' declared with 'error' attribute: demangle me
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 31 'expected-error': call to 'duplicate_errors' declared with 'error' attribute: two
error: diagnostics with 'warning' severity expected but not seen: 
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 29 'enabled-warning': call to 'quux' declared with 'warning' attribute: oh no quux
  File /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang/test/Frontend/backend-attribute-error-warning.c Line 32 'enabled-warning': call to 'duplicate_warnings' declared with 'warning' attribute: two
6 errors generated.

--

********************

Not sure why this change would mean NOT seeing the errors at all - is SelectionDAG finishing before it checks?

[dpaoliello]

Possible build break: https://lab.llvm.org/buildbot/#/builders/154/builds/20134

Fixed: #153302

[DavidSpickett]

Thanks for the fix, I was just getting around to looking at this. Our slower builders may continue to complain for a bit while they catch up but I can confirm the one you linked is green again.