[flang-commits] [flang] [clang] [flang] Enable alias tags pass by default (PR #73111)

via flang-commits flang-commits at lists.llvm.org
Wed Nov 22 03:53:24 PST 2023


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-driver

Author: Tom Eccles (tblah)

<details>
<summary>Changes</summary>

Enable by default when optimizing for speed.

For simplicity, only forward the flag to the frontend driver when it contradicts what is implied by the optimization level.

Since https://github.com/llvm/llvm-project/pull/72903 there are now no known performance regressions.

Original PR was https://github.com/llvm/llvm-project/pull/68597

---
Full diff: https://github.com/llvm/llvm-project/pull/73111.diff


8 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Flang.cpp (+20) 
- (modified) flang/include/flang/Tools/CLOptions.inc (+4-4) 
- (modified) flang/lib/Frontend/CompilerInvocation.cpp (+18-4) 
- (modified) flang/test/Driver/falias-analysis.f90 (+4) 
- (modified) flang/test/Driver/mlir-pass-pipeline.f90 (+2) 
- (modified) flang/test/Driver/optimization-remark.f90 (+9-13) 
- (modified) flang/test/Fir/basic-program.fir (+4) 
- (modified) flang/tools/tco/tco.cpp (+1) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 8bdd920c3dcbb796..9382433b94dadfd4 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -142,6 +142,26 @@ void Flang::addCodegenOptions(const ArgList &Args,
   if (shouldLoopVersion(Args))
     CmdArgs.push_back("-fversion-loops-for-stride");
 
+  Arg *aliasAnalysis = Args.getLastArg(options::OPT_falias_analysis,
+                                       options::OPT_fno_alias_analysis);
+  Arg *optLevel =
+      Args.getLastArg(options::OPT_Ofast, options::OPT_O, options::OPT_O4);
+  if (aliasAnalysis) {
+    bool falias_analysis =
+        aliasAnalysis->getOption().matches(options::OPT_falias_analysis);
+    // only pass on the argument if it does not match that implied by the
+    // optimization level
+    if (optLevel) {
+      if (!falias_analysis) {
+        CmdArgs.push_back("-fno-alias-analysis");
+      }
+    } else {
+      if (falias_analysis)
+        // requested alias analysis but no optimization enabled
+        CmdArgs.push_back("-falias-analysis");
+    }
+  }
+
   Args.addAllArgs(CmdArgs, {options::OPT_flang_experimental_hlfir,
                             options::OPT_flang_deprecated_no_hlfir,
                             options::OPT_flang_experimental_polymorphism,
diff --git a/flang/include/flang/Tools/CLOptions.inc b/flang/include/flang/Tools/CLOptions.inc
index c452c023b4a80ce1..5a17385fb3dae87a 100644
--- a/flang/include/flang/Tools/CLOptions.inc
+++ b/flang/include/flang/Tools/CLOptions.inc
@@ -157,11 +157,11 @@ inline void addDebugFoundationPass(mlir::PassManager &pm) {
       [&]() { return fir::createAddDebugFoundationPass(); });
 }
 
-inline void addFIRToLLVMPass(
-    mlir::PassManager &pm, llvm::OptimizationLevel optLevel = defaultOptLevel) {
+inline void addFIRToLLVMPass(mlir::PassManager &pm,
+    llvm::OptimizationLevel optLevel = defaultOptLevel, bool applyTbaa = true) {
   fir::FIRToLLVMPassOptions options;
   options.ignoreMissingTypeDescriptors = ignoreMissingTypeDescriptors;
-  options.applyTBAA = optLevel.isOptimizingForSpeed();
+  options.applyTBAA = applyTbaa;
   options.forceUnifiedTBAATree = useOldAliasTags;
   addPassConditionally(pm, disableFirToLlvmIr,
       [&]() { return fir::createFIRToLLVMPass(options); });
@@ -311,7 +311,7 @@ inline void createDefaultFIRCodeGenPassPipeline(
   if (config.VScaleMin != 0)
     pm.addPass(fir::createVScaleAttrPass({config.VScaleMin, config.VScaleMax}));
 
-  fir::addFIRToLLVMPass(pm, config.OptLevel);
+  fir::addFIRToLLVMPass(pm, config.OptLevel, config.AliasAnalysis);
 }
 
 /// Create a pass pipeline for lowering from MLIR to LLVM IR
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index cb4f2d6a6225205b..cfb1dd91ead30564 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -242,10 +242,24 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
                    clang::driver::options::OPT_fno_loop_versioning, false))
     opts.LoopVersioning = 1;
 
-  opts.AliasAnalysis =
-      args.hasFlag(clang::driver::options::OPT_falias_analysis,
-                   clang::driver::options::OPT_fno_alias_analysis,
-                   /*default=*/false);
+  bool aliasAnalysis = false;
+  bool noAliasAnalysis = false;
+  if (auto *arg =
+          args.getLastArg(clang::driver::options::OPT_falias_analysis,
+                          clang::driver::options::OPT_fno_alias_analysis)) {
+    if (arg->getOption().matches(clang::driver::options::OPT_falias_analysis))
+      aliasAnalysis = true;
+    else
+      noAliasAnalysis = true;
+  }
+  opts.AliasAnalysis = 0;
+  if (opts.OptimizationLevel > 0) {
+    if (!noAliasAnalysis)
+      opts.AliasAnalysis = 1;
+  } else {
+    if (aliasAnalysis)
+      opts.AliasAnalysis = 1;
+  }
 
   for (auto *a : args.filtered(clang::driver::options::OPT_fpass_plugin_EQ))
     opts.LLVMPassPlugins.push_back(a->getValue());
diff --git a/flang/test/Driver/falias-analysis.f90 b/flang/test/Driver/falias-analysis.f90
index f2c5dbde6d2c878c..1c74276974d47204 100644
--- a/flang/test/Driver/falias-analysis.f90
+++ b/flang/test/Driver/falias-analysis.f90
@@ -4,10 +4,14 @@
 ! RUN: %flang -c -emit-llvm -falias-analysis %s -o - | llvm-dis | FileCheck %s --check-prefix=CHECK-AA --check-prefix=CHECK-ALL
 ! RUN: %flang -c -emit-llvm -falias-analysis -fno-alias-analysis %s -o - | llvm-dis | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
 ! RUN: %flang -c -emit-llvm %s -o - | llvm-dis | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
+! RUN: %flang -c -emit-llvm -Ofast %s -o - | llvm-dis | FileCheck %s --check-prefix=CHECK-AA --check-prefix=CHECK-ALL
+! RUN: %flang -c -emit-llvm -Ofast -fno-alias-analysis %s -o - | llvm-dis | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
 
 ! RUN: %flang -fc1 -emit-llvm -falias-analysis %s -o - | FileCheck %s --check-prefix=CHECK-AA --check-prefix=CHECK-ALL
 ! RUN: %flang -fc1 -emit-llvm -falias-analysis -fno-alias-analysis %s -o - | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
 ! RUN: %flang -fc1 -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
+! RUN: %flang -fc1 -emit-llvm -O3 %s -o - | FileCheck %s --check-prefix=CHECK-AA --check-prefix=CHECK-ALL
+! RUN: %flang -fc1 -emit-llvm -O3 -fno-alias-analysis %s -o - | FileCheck %s --check-prefix=CHECK-NOAA --check-prefix=CHECK-ALL
 
 subroutine simple(a)
   integer, intent(inout) :: a(:)
diff --git a/flang/test/Driver/mlir-pass-pipeline.f90 b/flang/test/Driver/mlir-pass-pipeline.f90
index 7f92ec25bef98ec7..3d8c42f123e2eb06 100644
--- a/flang/test/Driver/mlir-pass-pipeline.f90
+++ b/flang/test/Driver/mlir-pass-pipeline.f90
@@ -51,6 +51,8 @@
 
 ! ALL-NEXT: 'func.func' Pipeline
 ! ALL-NEXT:   PolymorphicOpConversion
+! O2-NEXT:  AddAliasTags
+! O2-NEXT:  'func.func' Pipeline
 ! ALL-NEXT:   CFGConversion
 
 ! ALL-NEXT: SCFToControlFlow
diff --git a/flang/test/Driver/optimization-remark.f90 b/flang/test/Driver/optimization-remark.f90
index 13fc24346eac68b8..20ff9eb59a6702d6 100644
--- a/flang/test/Driver/optimization-remark.f90
+++ b/flang/test/Driver/optimization-remark.f90
@@ -41,28 +41,24 @@
 ! Once we start filtering, this is reduced to 1 one of the loop passes.
 
 ! PASS-REGEX-LOOP-ONLY-NOT:     optimization-remark.f90:77:7: remark: hoisting load [-Rpass=licm]
-! PASS-REGEX-LOOP-ONLY:         optimization-remark.f90:83:5: remark: Loop deleted because it is invariant [-Rpass=loop-delete]
+! PASS-REGEX-LOOP-ONLY:         optimization-remark.f90:79:5: remark: Loop deleted because it is invariant [-Rpass=loop-delete]
 
 ! MISSED-REGEX-LOOP-ONLY-NOT:   optimization-remark.f90:77:7: remark: failed to hoist load with loop-invariant address because load is conditionally executed [-Rpass-missed=licm]
-! MISSED-REGEX-LOOP-ONLY:       optimization-remark.f90:76:4: remark: loop not vectorized [-Rpass-missed=loop-vectorize]
+! MISSED-REGEX-LOOP-ONLY:       optimization-remark.f90:72:4: remark: loop not vectorized [-Rpass-missed=loop-vectorize]
 
 
-! ANALYSIS-REGEX-LOOP-ONLY:     optimization-remark.f90:79:7: remark: loop not vectorized: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
-! ANALYSIS-REGEX-LOOP-ONLY:     Unknown data dependence. Memory location is the same as accessed at optimization-remark.f90:78:7 [-Rpass-analysis=loop-vectorize]
+! ANALYSIS-REGEX-LOOP-ONLY:     optimization-remark.f90:73:7: remark: loop not vectorized: cannot identify array bounds [-Rpass-analysis=loop-vectorize]
 ! ANALYSIS-REGEX-LOOP-ONLY-NOT: remark: {{.*}}: IR instruction count changed from {{[0-9]+}} to {{[0-9]+}}; Delta: {{-?[0-9]+}} [-Rpass-analysis=size-info]
 
-! PASS:                         optimization-remark.f90:77:7: remark: hoisting load [-Rpass=licm]
-! PASS:                         optimization-remark.f90:83:5: remark: Loop deleted because it is invariant [-Rpass=loop-delete]
+! PASS:                         optimization-remark.f90:79:5: remark: Loop deleted because it is invariant [-Rpass=loop-delete]
 
-! MISSED:                       optimization-remark.f90:77:7: remark: failed to hoist load with loop-invariant address because load is conditionally executed [-Rpass-missed=licm]
-! MISSED:                       optimization-remark.f90:76:4: remark: loop not vectorized [-Rpass-missed=loop-vectorize]
-! MISSED-NOT:                   optimization-remark.f90:79:7: remark: loop not vectorized: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
+! MISSED:                       optimization-remark.f90:73:7: remark: failed to move load with loop-invariant address because the loop may invalidate its value [-Rpass-missed=licm]
+! MISSED:                       optimization-remark.f90:72:4: remark: loop not vectorized [-Rpass-missed=loop-vectorize]
+! MISSED-NOT:                   optimization-remark.f90:75:7: remark: loop not vectorized: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
 ! MISSED-NOT:                   Unknown data dependence. Memory location is the same as accessed at optimization-remark.f90:78:7 [-Rpass-analysis=loop-vectorize]
 
-! ANALYSIS:                     optimization-remark.f90:79:7: remark: loop not vectorized: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
-! ANALYSIS:                     Unknown data dependence. Memory location is the same as accessed at optimization-remark.f90:78:7 [-Rpass-analysis=loop-vectorize]
-! ANALYSIS:                     remark: {{.*}}: IR instruction count changed from {{[0-9]+}} to {{[0-9]+}}; Delta: {{-?[0-9]+}} [-Rpass-analysis=size-info]
-! ANALYSIS-NOT:                 optimization-remark.f90:77:7: remark: failed to hoist load with loop-invariant address because load is conditionally executed [-Rpass-missed=licm]
+! ANALYSIS:                     optimization-remark.f90:74:7: remark: loop not vectorized: unsafe dependent memory operations in loop.
+! ANALYSIS:                     remark: {{.*}} instructions in function [-Rpass-analysis=asm-printer]
 
 subroutine swap_real(a1, a2)
    implicit none
diff --git a/flang/test/Fir/basic-program.fir b/flang/test/Fir/basic-program.fir
index 0e82f7dfdedb447d..d8a9e74c318ce186 100644
--- a/flang/test/Fir/basic-program.fir
+++ b/flang/test/Fir/basic-program.fir
@@ -57,6 +57,10 @@ func.func @_QQmain() {
 
 // PASSES-NEXT: 'func.func' Pipeline
 // PASSES-NEXT:   PolymorphicOpConversion
+
+// PASSES-NEXT: AddAliasTags
+
+// PASSES-NEXT: 'func.func' Pipeline
 // PASSES-NEXT:   CFGConversion
 
 // PASSES-NEXT: SCFToControlFlow
diff --git a/flang/tools/tco/tco.cpp b/flang/tools/tco/tco.cpp
index 31d6bac142dc421b..a649535a39b74b31 100644
--- a/flang/tools/tco/tco.cpp
+++ b/flang/tools/tco/tco.cpp
@@ -120,6 +120,7 @@ compileFIR(const mlir::PassPipelineCLParser &passPipeline) {
       return mlir::failure();
   } else {
     MLIRToLLVMPassPipelineConfig config(llvm::OptimizationLevel::O2);
+    config.AliasAnalysis = true; // enabled when optimizing for speed
     if (codeGenLLVM) {
       // Run only CodeGen passes.
       fir::createDefaultFIRCodeGenPassPipeline(pm, config);

``````````

</details>


https://github.com/llvm/llvm-project/pull/73111


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