[clang] 005fc11 - [PGO] Change ThinLTO test for targets with loop unrolling disabled

[Thomas Preud'homme via cfe-commits]

Author: Sherwin da Cruz
Date: 2021-09-16T11:13:16+01:00
New Revision: 005fc11ebdd6e1af29efee3d7c5da86f56138414

URL: https://github.com/llvm/llvm-project/commit/005fc11ebdd6e1af29efee3d7c5da86f56138414
DIFF: https://github.com/llvm/llvm-project/commit/005fc11ebdd6e1af29efee3d7c5da86f56138414.diff

LOG: [PGO] Change ThinLTO test for targets with loop unrolling disabled

I am working on a target in a downstream LLVM repo, and it seems that if a target backend chooses to disable loop unrolling this test would fail. A solution would be to modify the test to search for a different string instead.

The specific test checks for `if.true.direct_targ` which appears in the output when thinlto is not used (ie samplepgo). The same is true for `if.false.orig_indirect`.

However, if a target disables loop unrolling in the backend, the test fails as  `if.true.direct_targ` no longer appears, though `if.false.orig_indirect` still does. This can be seen by using a clang pragma to disable loop unrolling in the `unroll()` function.

For reference, the following files are the outputs of the last 2 test functions being compiled as the test case does, with and without thinlto, and with and without loop unrolling on the latest x86 clang build. The loop unrolling pragma was used to simulate the loop unrolling being disabled in a backend.
```
// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o out.ll
// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o out.ll
```

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D109234

Added: 
    

Modified: 
    clang/test/CodeGen/pgo-sample-thinlto-summary.c

Removed: 
    


################################################################################
diff  --git a/clang/test/CodeGen/pgo-sample-thinlto-summary.c b/clang/test/CodeGen/pgo-sample-thinlto-summary.c
index eae35a040e5f8..1de2298320e50 100644
--- a/clang/test/CodeGen/pgo-sample-thinlto-summary.c
+++ b/clang/test/CodeGen/pgo-sample-thinlto-summary.c
@@ -1,9 +1,7 @@
-// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=SAMPLEPGO
-// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=THINLTO
-// RUN: %clang_cc1 -O2 -fexperimental-new-pass-manager -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=SAMPLEPGO
-// RUN: %clang_cc1 -O2 -fexperimental-new-pass-manager -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=THINLTO
-// Checks if hot call is inlined by normal compile, but not inlined by
-// thinlto compile.
+// RUN: %clang_cc1 -mllvm -debug-pass=Structure -O2 -fno-experimental-new-pass-manager -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=SAMPLEPGO-OLDPM
+// RUN: %clang_cc1 -mllvm -debug-pass=Structure -O2 -fno-experimental-new-pass-manager -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=THINLTO-OLDPM
+// RUN: %clang_cc1 -fdebug-pass-manager -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=SAMPLEPGO
+// RUN: %clang_cc1 -fdebug-pass-manager -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=THINLTO
 
 int baz(int);
 int g;
@@ -13,6 +11,27 @@ void foo(int n) {
     g += baz(i);
 }
 
+// Checks that loop unroll and icp are invoked by normal compile, but not thinlto compile.
+
+// SAMPLEPGO:               Running pass: PGOIndirectCallPromotion on [module]
+// SAMPLEPGO:               Running pass: LoopUnrollPass on bar
+
+// SAMPLEPGO-OLDPM:         PGOIndirectCallPromotion
+// SAMPLEPGO-OLDPM:         Unroll loops
+// SAMPLEPGO-OLDPM:         Unroll loops
+
+// THINLTO-NOT:             Running pass: PGOIndirectCallPromotion on [module]
+// THINLTO-NOT:             Running pass: LoopUnrollPass on bar
+
+// THINLTO-OLDPM-NOT:       PGOIndirectCallPromotion
+// The first Unroll loop pass is the createSimpleLoopUnrollPass that unrolls and peels
+// loops with small constant trip counts. The second one is skipped by ThinLTO.
+// THINLTO-OLDPM:           Unroll loops
+// THINLTO-OLDPM-NOT:       Unroll loops
+
+
+// Checks if hot call is inlined by normal compile, but not inlined by
+// thinlto compile.
 // SAMPLEPGO-LABEL: define {{(dso_local )?}}void @bar
 // THINLTO-LABEL: define {{(dso_local )?}}void @bar
 // SAMPLEPGO-NOT: call{{.*}}foo
@@ -20,27 +39,4 @@ void foo(int n) {
 void bar(int n) {
   for (int i = 0; i < n; i++)
     foo(i);
-}
-
-// Checks if loop unroll is invoked by normal compile, but not thinlto compile.
-// SAMPLEPGO-LABEL: define {{(dso_local )?}}void @unroll
-// THINLTO-LABEL: define {{(dso_local )?}}void @unroll
-// SAMPLEPGO: call{{.*}}baz
-// SAMPLEPGO: call{{.*}}baz
-// THINLTO: call{{.*}}baz
-// THINLTO-NOT: call{{.*}}baz
-void unroll() {
-  for (int i = 0; i < 2; i++)
-    baz(i);
-}
-
-// Checks that icp is not invoked for ThinLTO, but invoked for normal samplepgo.
-// SAMPLEPGO-LABEL: define {{(dso_local )?}}void @icp
-// THINLTO-LABEL: define {{(dso_local )?}}void @icp
-// SAMPLEPGO: if.true.direct_targ
-// FIXME: the following condition needs to be reversed once
-//        LTOPreLinkDefaultPipeline is customized.
-// THINLTO-NOT: if.true.direct_targ
-void icp(void (*p)()) {
-  p();
-}
+}
\ No newline at end of file