Make likelihood lit test less brittle

[Mordante]

Summary

Jeremy Morse discovered an issue with the lit test introduced in D88363. The test gives different results for Sony's -O1.

The test needs to run at -O1 otherwise the likelihood attribute will be ignored. Instead of running all -O1 passes it only runs the lower-expect pass which is needed to lower __builtin_expect.

@jmorse can you verify this fixes Sony's issue?

[jmorse]

This fixes things for us, and by limiting to one optimisation pass it's much less brittle for the future -- much appreciated!

[Mordante]

In D89204#2324563, @jmorse wrote:

This fixes things for us, and by limiting to one optimisation pass it's much less brittle for the future -- much appreciated!

I'm glad to hear it fixes your issue. Thanks for testing!

clang/test/CodeGenCXX/attr-likelihood-if-vs-builtin-expect.cpp

-// RUN: %clang_cc1 -O1 -emit-llvm %s -o - -triple=x86_64-linux-gnu | FileCheck %s
+// RUN: %clang_cc1 -O1 -disable-llvm-passes -emit-llvm %s -o - -triple=x86_64-linux-gnu | opt --lower-expect -S | FileCheck %s
 
 // Verifies the output of __builtin_expect versus the output of the likelihood
 // attributes. They should generate the same probabilities for the branches.
 
 extern bool a();
 extern bool b();
 extern bool c();
 
 void ab1(int &i) {
   // CHECK-LABEL: define{{.*}}ab1
-  // CHECK: br {{.*}} !prof !2
-  // CHECK: br {{.*}} !prof !2
-  // CHECK: br {{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
+  // CHECK: br {{.*}} !prof !6
+  // CHECK: br {{.*}} !prof !6
   if (__builtin_expect(a() && b() && a(), 1)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void al(int &i) {
   // CHECK-LABEL: define{{.*}}al
-  // CHECK: br {{.*}} !prof !2
-  // CHECK: br {{.*}} !prof !2
-  // CHECK: br {{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
+  // CHECK: br {{.*}} !prof !6
+  // CHECK: br {{.*}} !prof !6
   if (a() && b() && c()) [[likely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void ab0(int &i) {
   // CHECK-LABEL: define{{.*}}ab0
-  // CHECK: br {{.*}}else{{$}}
-  // CHECK: br {{.*}}else{{$}}
-  // CHECK: br {{.*}} !prof !8
+  // CHECK: br {{.*}}end{{$}}
+  // CHECK: br {{.*}}end{{$}}
+  // CHECK: br {{.*}}end{{$}}
+  // CHECK: br {{.*}} !prof !10
   if (__builtin_expect(a() && b() && c(), 0)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void au(int &i) {
   // CHECK-LABEL: define{{.*}}au
   // CHECK: br {{.*}}else{{$}}
   // CHECK: br {{.*}}else{{$}}
-  // CHECK: br {{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
   if (a() && b() && c()) [[unlikely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void ob1(int &i) {
   // CHECK-LABEL: define{{.*}}ob1
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}rhs{{$}}
-  // CHECK: br {{.*}} !prof !2
+  // CHECK: br {{.*}}end{{$}}
+  // CHECK: br {{.*}} !prof !6
   if (__builtin_expect(a() || b() || a(), 1)) {
     i = 0;
   } else {
     --i;
   }
 }
 
 void ol(int &i) {
   // CHECK-LABEL: define{{.*}}ol
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}false2{{$}}
-  // CHECK: br {{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
   if (a() || b() || c()) [[likely]] {
     i = 0;
   } else {
     --i;
   }
 }
 
 void ob0(int &i) {
   // CHECK-LABEL: define{{.*}}ob0
-  // CHECK: br {{.*}} !prof !8
-  // CHECK: br {{.*}} !prof !8
-  // CHECK: br {{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !10
   if (__builtin_expect(a() || b() || c(), 0)) {
     i = 0;
   } else {
     --i;
   }
 }
 
 void ou(int &i) {
   // CHECK-LABEL: define{{.*}}ou
-  // CHECK: br {{.*}} !prof !8
-  // CHECK: br {{.*}} !prof !8
-  // CHECK: br {{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !10
   if (a() || b() || c()) [[unlikely]] {
     i = 0;
   } else {
     --i;
   }
 }
 
 void nb1(int &i) {
   // CHECK-LABEL: define{{.*}}nb1
-  // CHECK: storemerge{{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !6
   if (__builtin_expect(!a(), 1)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void nl(int &i) {
   // CHECK-LABEL: define{{.*}}nl
-  // CHECK: storemerge{{.*}} !prof !8
-  if (!a()) [[likely]] {
+  // CHECK: br {{.*}} !prof !6
+  if (bool d = !a()) [[likely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void nb0(int &i) {
   // CHECK-LABEL: define{{.*}}nb0
-  // CHECK: storemerge{{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !10
   if (__builtin_expect(!a(), 0)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void nu(int &i) {
   // CHECK-LABEL: define{{.*}}nu
-  // CHECK: storemerge{{.*}} !prof !2
-  if (!a()) [[unlikely]] {
+  // CHECK: br {{.*}} !prof !10
+  if (bool d = !a()) [[unlikely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void tb1(int &i) {
   // CHECK-LABEL: define{{.*}}tb1
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: storemerge{{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
   if (__builtin_expect(a() ? b() : c(), 1)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void tl(int &i) {
   // CHECK-LABEL: define{{.*}}tl
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: storemerge{{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
   if (bool d = a() ? b() : c()) [[likely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void tl2(int &i) {
   // CHECK-LABEL: define{{.*}}tl
   // CHECK: br {{.*}}false{{$}}
-  // CHECK: br {{.*}} !prof !2
-  // CHECK: br {{.*}} !prof !2
+  // CHECK: br {{.*}} !prof !6
+  // CHECK: br {{.*}} !prof !6
   if (a() ? b() : c()) [[likely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void tb0(int &i) {
   // CHECK-LABEL: define{{.*}}tb0
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: storemerge{{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
   if (__builtin_expect(a() ? b() : c(), 0)) {
     ++i;
   } else {
     --i;
   }
 }
 
 void tu(int &i) {
   // CHECK-LABEL: define{{.*}}tu
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: storemerge{{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
   if (bool d = a() ? b() : c()) [[unlikely]] {
     ++i;
   } else {
     --i;
   }
 }
 
 void tu2(int &i) {
   // CHECK-LABEL: define{{.*}}tu
   // CHECK: br {{.*}}false{{$}}
-  // CHECK: br {{.*}} !prof !8
-  // CHECK: br {{.*}} !prof !8
+  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !10
   if (a() ? b() : c()) [[unlikely]] {
     ++i;
   } else {
     --i;
   }
 }
 
-// CHECK: !2 = !{!"branch_weights", i32 2000, i32 1}
-// CHECK: !8 = !{!"branch_weights", i32 1, i32 2000}
+// CHECK: !6 = !{!"branch_weights", i32 2000, i32 1}
+// CHECK: !10 = !{!"branch_weights", i32 1, i32 2000}