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llvm-project/clang/test/CodeGenCXX/fno-unroll-loops-metadata.cpp

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[Clang] Add llvm.loop.unroll.disable to loops with -fno-unroll-loops. Currently Clang does not respect -fno-unroll-loops during LTO. During D76916 it was suggested to respect -fno-unroll-loops on a TU basis. This patch uses the existing llvm.loop.unroll.disable metadata to disable loop unrolling explicitly for each loop in the TU if unrolling is disabled. This should ensure that loops from TUs compiled with -fno-unroll-loops are skipped by the unroller during LTO. This also means that if a loop from a TU with -fno-unroll-loops gets inlined into a TU without this option, the loop won't be unrolled. Due to the fact that some transforms might drop loop metadata, there potentially are cases in which we still unroll loops from TUs with -fno-unroll-loops. I think we should fix those issues rather than introducing a function attribute to disable loop unrolling during LTO. Improving the metadata handling will benefit other use cases, like various loop pragmas, too. And it is an improvement to clang completely ignoring -fno-unroll-loops during LTO. If that direction looks good, we can use a similar approach to also respect -fno-vectorize during LTO, at least for LoopVectorize. In the future, this might also allow us to remove the UnrollLoops option LLVM's PassManagerBuilder. Reviewers: Meinersbur, hfinkel, dexonsmith, tejohnson Reviewed By: Meinersbur, tejohnson Differential Revision: https://reviews.llvm.org/D77058
2020-04-07 20:43:48 +08:00
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s -O0 -disable-llvm-optzns -fno-unroll-loops | FileCheck --check-prefix=NO_UNROLL_MD %s
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s -O1 -disable-llvm-optzns -fno-unroll-loops | FileCheck --check-prefix=UNROLL_DISABLED_MD %s
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s -O2 -disable-llvm-optzns -fno-unroll-loops | FileCheck --check-prefix=UNROLL_DISABLED_MD %s
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s -O3 -disable-llvm-optzns -fno-unroll-loops | FileCheck --check-prefix=UNROLL_DISABLED_MD %s
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s -O3 -disable-llvm-optzns | FileCheck --check-prefix=NO_UNROLL_MD %s
// NO_UNROLL_MD-NOT: llvm.loop
// Verify unroll.disable metadata is added to while loop with -fno-unroll-loops
// and optlevel > 0.
void while_test(int *List, int Length) {
// UNROLL_DISABLED_MD: define {{.*}} @_Z10while_test
int i = 0;
while (i < Length) {
// UNROLL_DISABLED_MD: br label {{.*}}, !llvm.loop ![[LOOP_1:.*]]
List[i] = i * 2;
i++;
}
}
// Verify unroll.disable metadata is added to do-while loop with
// -fno-unroll-loops and optlevel > 0.
void do_test(int *List, int Length) {
// UNROLL_DISABLED_MD: define {{.*}} @_Z7do_test
int i = 0;
do {
// UNROLL_DISABLED_MD: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[LOOP_2:.*]]
List[i] = i * 2;
i++;
} while (i < Length);
}
// Verify unroll.disable metadata is added to while loop with -fno-unroll-loops
// and optlevel > 0.
void for_test(int *List, int Length) {
// UNROLL_DISABLED_MD: define {{.*}} @_Z8for_test
for (int i = 0; i < Length; i++) {
// UNROLL_DISABLED_MD: br label {{.*}}, !llvm.loop ![[LOOP_3:.*]]
List[i] = i * 2;
}
}
// UNROLL_DISABLED_MD: ![[LOOP_1]] = distinct !{![[LOOP_1]], ![[UNROLL_DISABLE:.*]]}
// UNROLL_DISABLED_MD: ![[UNROLL_DISABLE]] = !{!"llvm.loop.unroll.disable"}
// UNROLL_DISABLED_MD: ![[LOOP_2]] = distinct !{![[LOOP_2:.*]], ![[UNROLL_DISABLE:.*]]}
// UNROLL_DISABLED_MD: ![[LOOP_3]] = distinct !{![[LOOP_3]], ![[UNROLL_DISABLE:.*]]}