[clang] [llvm] [Clang] Fix nomerge attribute not working with __builtin_trap(), __debugbreak(), __builtin_verbose_trap() (PR #101549)

[Zequan Wu via cfe-commits]

https://github.com/ZequanWu created https://github.com/llvm/llvm-project/pull/101549

1. It fixes the problem that llvm.trap() not getting the nomerge attribute.
2. It sets nomerge flag for the node if the instruction has nomerge arrtibute.

This is a copy of https://reviews.llvm.org/D146164. This only attempts to fixe `nomerge` for `__builtin_trap()`, `__debugbreak()`, `__builtin_verbose_trap()`, not working for non-trap builtins.

Fixes #53011 

>From ea1e66a670cf689ef904b59165eae0a978b9bdc2 Mon Sep 17 00:00:00 2001
From: Zequan Wu <zequanwu at google.com>
Date: Thu, 1 Aug 2024 11:59:50 -0700
Subject: [PATCH] [Clang] Fix nomerge attribute not working with
 __builtin_trap(), __debugbreak(), __builtin_verbose_trap()

---
 clang/lib/CodeGen/CGExpr.cpp                  |  2 +
 clang/test/CodeGen/attr-nomerge.cpp           |  8 +-
 .../SelectionDAG/SelectionDAGBuilder.cpp      |  4 +-
 llvm/test/CodeGen/X86/nomerge.ll              | 92 +++++++++++++++++++
 4 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 5f58a64d8386c..9f18642ebbbf2 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3883,6 +3883,8 @@ llvm::CallInst *CodeGenFunction::EmitTrapCall(llvm::Intrinsic::ID IntrID) {
     TrapCall->addFnAttr(A);
   }
 
+  if (InNoMergeAttributedStmt)
+    TrapCall->addFnAttr(llvm::Attribute::NoMerge);
   return TrapCall;
 }
 
diff --git a/clang/test/CodeGen/attr-nomerge.cpp b/clang/test/CodeGen/attr-nomerge.cpp
index 7305fb73cf1dc..b643920adde49 100644
--- a/clang/test/CodeGen/attr-nomerge.cpp
+++ b/clang/test/CodeGen/attr-nomerge.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -fms-extensions -o - | FileCheck %s
 
 class A {
 public:
@@ -42,6 +42,9 @@ void foo(int i, A *ap, B *bp) {
 
   A *newA = new B();
   delete newA;
+  [[clang::nomerge]] __builtin_trap();
+  [[clang::nomerge]] __debugbreak();
+  [[clang::nomerge]] __builtin_verbose_trap("check null", "Argument must not be null.");
 }
 
 int g(int i);
@@ -97,6 +100,9 @@ void something_else_again() {
 // CHECK: load ptr, ptr
 // CHECK: %[[AG:.*]] = load ptr, ptr
 // CHECK-NEXT: call void %[[AG]](ptr {{.*}}) #[[ATTR1]]
+// CHECK: call void @llvm.trap() #[[ATTR0]]
+// CHECK: call void @llvm.debugtrap() #[[ATTR0]]
+// CHECK: call void @llvm.trap() #[[ATTR0]]
 // CHECK: call void  @_ZN1AD1Ev(ptr {{.*}}) #[[ATTR1]]
 
 // CHECK-DAG: attributes #[[ATTR0]] = {{{.*}}nomerge{{.*}}}
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 9f5e6466309e9..a035fee6aafca 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -7448,6 +7448,8 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
         break;
       default: llvm_unreachable("unknown trap intrinsic");
       }
+      DAG.addNoMergeSiteInfo(DAG.getRoot().getNode(),
+                             I.hasFnAttr(Attribute::NoMerge));
       return;
     }
     TargetLowering::ArgListTy Args;
@@ -7464,7 +7466,7 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
         DAG.getExternalSymbol(TrapFuncName.data(),
                               TLI.getPointerTy(DAG.getDataLayout())),
         std::move(Args));
-
+    CLI.NoMerge = I.hasFnAttr(Attribute::NoMerge);
     std::pair<SDValue, SDValue> Result = TLI.LowerCallTo(CLI);
     DAG.setRoot(Result.second);
     return;
diff --git a/llvm/test/CodeGen/X86/nomerge.ll b/llvm/test/CodeGen/X86/nomerge.ll
index efbadf5b6911f..d3e6feae87108 100644
--- a/llvm/test/CodeGen/X86/nomerge.ll
+++ b/llvm/test/CodeGen/X86/nomerge.ll
@@ -62,4 +62,96 @@ if.end:
 
 declare dso_local void @bar()
 
+define void @nomerge_trap(i32 %i) {
+; CHECK-LABEL: nomerge_trap:
+; CHECK:      # %bb.0: # %entry
+; CHECK:      # %bb.1: # %entry
+; CHECK:      # %bb.2: # %if.then
+; CHECK-NEXT: ud2
+; CHECK-NEXT: LBB1_3: # %if.then2
+; CHECK-NEXT: ud2
+; CHECK-NEXT: .LBB1_4: # %if.end3
+; CHECK-NEXT: ud2
+entry:
+  switch i32 %i, label %if.end3 [
+    i32 5, label %if.then
+    i32 7, label %if.then2
+  ]
+
+if.then:
+  tail call void @llvm.trap() #0
+  unreachable
+
+if.then2:
+  tail call void @llvm.trap() #0
+  unreachable
+
+if.end3:
+  tail call void @llvm.trap() #0
+  unreachable
+}
+
+declare dso_local void @llvm.trap()
+
+define void @nomerge_debugtrap(i32 %i) {
+; CHECK-LABEL: nomerge_debugtrap:
+; CHECK:      # %bb.0: # %entry
+; CHECK:      # %bb.1: # %entry
+; CHECK:      # %bb.2: # %if.then
+; CHECK-NEXT: int3
+; CHECK-NEXT: LBB2_3: # %if.then2
+; CHECK-NEXT: int3
+; CHECK-NEXT: .LBB2_4: # %if.end3
+; CHECK-NEXT: int3
+entry:
+  switch i32 %i, label %if.end3 [
+    i32 5, label %if.then
+    i32 7, label %if.then2
+  ]
+
+if.then:
+  tail call void @llvm.debugtrap() #0
+  unreachable
+
+if.then2:
+  tail call void @llvm.debugtrap() #0
+  unreachable
+
+if.end3:
+  tail call void @llvm.debugtrap() #0
+  unreachable
+}
+
+define void @nomerge_named_debugtrap(i32 %i) {
+; CHECK-LABEL: nomerge_named_debugtrap:
+; CHECK:      # %bb.0: # %entry
+; CHECK:      # %bb.1: # %entry
+; CHECK:      # %bb.2: # %if.then
+; CHECK-NEXT: callq trap_func at PLT
+; CHECK-NEXT: LBB3_3: # %if.then2
+; CHECK-NEXT: callq trap_func at PLT
+; CHECK-NEXT: .LBB3_4: # %if.end3
+; CHECK-NEXT: callq trap_func at PLT
+entry:
+  switch i32 %i, label %if.end3 [
+    i32 5, label %if.then
+    i32 7, label %if.then2
+  ]
+
+if.then:
+  tail call void @llvm.debugtrap() #1
+  unreachable
+
+if.then2:
+  tail call void @llvm.debugtrap() #1
+  unreachable
+
+if.end3:
+  tail call void @llvm.debugtrap() #1
+  unreachable
+}
+
+declare dso_local void @llvm.debugtrap()
+
 attributes #0 = { nomerge }
+attributes #1 = { nomerge "trap-func-name"="trap_func" }