[PATCH] D92623: [inliner] Apply nomerge attribute to all call sites inside inlined function.

[Zequan Wu via Phabricator via llvm-commits]

zequanwu created this revision.
zequanwu added reviewers: rnk, craig.topper.
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[[clang::nomerge]] statement attribute stops optimizer from merging multiple calls into one. When inlining happends, the attribute got lost, which is not desired.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D92623

Files:
  llvm/lib/Transforms/Utils/InlineFunction.cpp
  llvm/test/Transforms/Inline/inline_nomerge.ll


Index: llvm/test/Transforms/Inline/inline_nomerge.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Inline/inline_nomerge.ll
@@ -0,0 +1,37 @@
+; Check nomerge attribute at call sites applying to all call sites inside the inlined function.
+; RUN: opt < %s -O3 -S | FileCheck %s
+
+declare void @f()
+declare void @g()
+
+define void @bar() {
+entry:
+    call void @f()
+    call void @g()
+    ret void
+}
+
+define void @foo(i32 %i) {
+entry:
+  switch i32 %i, label %if.end [
+    i32 5, label %if.then
+    i32 7, label %if.then2
+  ]
+
+if.then:
+  call void @bar() #0 ; CHECK:      call void @f() #0
+                      ; CHECK-NEXT: call void @g() #0
+  br label %if.end
+
+if.then2:
+  call void @bar() #0 ; CHECK: call void @f() #0
+                      ; CHECK-NEXT: call void @g() #0
+  br label %if.end
+
+if.end:
+  call void @bar() #0 ; CHECK: call void @f() #0
+                      ; CHECK-NEXT: call void @g() #0
+  ret void
+}
+
+attributes #0 = { nomerge }
Index: llvm/lib/Transforms/Utils/InlineFunction.cpp
===================================================================
--- llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1970,6 +1970,10 @@
         if (!CI)
           continue;
 
+        // Apply nomerge attribute to all call sites inside inlined function.
+        if (CB.hasFnAttr(Attribute::NoMerge))
+          CI->setCannotMerge();
+
         // Forward varargs from inlined call site to calls to the
         // ForwardVarArgsTo function, if requested, and to musttail calls.
         if (!VarArgsToForward.empty() &&


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