https://github.com/madhur13490 updated https://github.com/llvm/llvm-project/pull/216920
>From 2c9a2cfe3e40ab9ab8c3cf90af8895e37414c086 Mon Sep 17 00:00:00 2001 From: Madhur Amilkanthwar <[email protected]> Date: Fri, 14 Aug 2026 09:32:57 -0700 Subject: [PATCH 1/2] [Clang][Flang] Enable loop interchange by default at -O3 PR #124911 enabled the LoopInterchange pass by default in the LLVM optimization pipeline (the PipelineTuningOptions default used by opt), but the clang and flang frontends override that default and keep it off. As a result, driving the compiler through clang or flang never runs loop interchange unless -floop-interchange is passed explicitly. Default the -floop-interchange flag on at -O3 for both frontends so they match the pipeline default. The decision is made in the frontend (-cc1) for both clang and flang, mirroring -funroll-loops; the flang driver only forwards an explicit -f[no-]loop-interchange. Lower opt levels and an explicit -fno-loop-interchange keep it off. --- clang/lib/Driver/ToolChains/CommonArgs.cpp | 7 ++++--- clang/lib/Frontend/CompilerInvocation.cpp | 4 +++- clang/test/Driver/clang_f_opts.c | 7 +++++++ flang/lib/Frontend/CompilerInvocation.cpp | 6 ++++-- flang/test/Driver/loop-interchange.f90 | 14 +++++++------- 5 files changed, 25 insertions(+), 13 deletions(-) diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp index a76f4aa6ae853..ad6280ae45277 100644 --- a/clang/lib/Driver/ToolChains/CommonArgs.cpp +++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp @@ -3564,9 +3564,10 @@ void tools::handleVectorizeSLPArgs(const ArgList &Args, void tools::handleInterchangeLoopsArgs(const ArgList &Args, ArgStringList &CmdArgs) { - if (Args.hasFlag(options::OPT_floop_interchange, - options::OPT_fno_loop_interchange, false)) - CmdArgs.push_back("-floop-interchange"); + // Forward the user's explicit choice; the frontend applies the -O3 + // default when neither flag is present. + Args.AddLastArg(CmdArgs, options::OPT_floop_interchange, + options::OPT_fno_loop_interchange); } std::string tools::complexRangeKindToStr(LangOptions::ComplexRangeKind Range) { diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp index 70fc346d85920..f023df260d55e 100644 --- a/clang/lib/Frontend/CompilerInvocation.cpp +++ b/clang/lib/Frontend/CompilerInvocation.cpp @@ -1945,8 +1945,10 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, Opts.UnrollLoops = Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops, (Opts.OptimizationLevel > 1)); + // Loop interchange is only enabled by default at -O3. Opts.InterchangeLoops = - Args.hasFlag(OPT_floop_interchange, OPT_fno_loop_interchange, false); + Args.hasFlag(OPT_floop_interchange, OPT_fno_loop_interchange, + (Opts.OptimizationLevel == 3)); Opts.FuseLoops = Args.hasFlag(OPT_fexperimental_loop_fusion, OPT_fno_experimental_loop_fusion, false); Opts.BinutilsVersion = diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c index 5871f1580d6b7..c14885b04ad6f 100644 --- a/clang/test/Driver/clang_f_opts.c +++ b/clang/test/Driver/clang_f_opts.c @@ -51,6 +51,13 @@ // RUN: %clang -### -S -floop-interchange -fno-loop-interchange %s 2>&1 | FileCheck -check-prefix=CHECK-NO-INTERCHANGE-LOOPS %s // CHECK-INTERCHANGE-LOOPS: "-floop-interchange" // CHECK-NO-INTERCHANGE-LOOPS: "-fno-loop-interchange" +// +// Loop interchange is enabled by default only at -O3. +// RUN: %clang -c -mllvm -print-pipeline-passes -O3 %s -o /dev/null 2>&1 | FileCheck --check-prefixes=INTERCHANGE-ON %s +// RUN: %clang -c -mllvm -print-pipeline-passes -O2 %s -o /dev/null 2>&1 | FileCheck --check-prefixes=INTERCHANGE-OFF %s +// RUN: %clang -c -fno-loop-interchange -mllvm -print-pipeline-passes -O3 %s -o /dev/null 2>&1 | FileCheck --check-prefixes=INTERCHANGE-OFF %s +// INTERCHANGE-ON: loop-interchange +// INTERCHANGE-OFF-NOT: loop-interchange // RUN: %clang -### -S -fexperimental-loop-fusion %s -o /dev/null 2>&1 | FileCheck -check-prefix=CHECK-FUSE-LOOPS %s // CHECK-FUSE-LOOPS: "-fexperimental-loop-fusion" diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp index b57bc4583be38..d50dc4878e60d 100644 --- a/flang/lib/Frontend/CompilerInvocation.cpp +++ b/flang/lib/Frontend/CompilerInvocation.cpp @@ -320,8 +320,10 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts, clang::options::OPT_fno_fp_sum_reassociation, false)) opts.SplitSumExpressionTree = 1; - if (args.getLastArg(clang::options::OPT_floop_interchange)) - opts.InterchangeLoops = 1; + // Loop interchange is only enabled by default at -O3. + opts.InterchangeLoops = args.hasFlag(clang::options::OPT_floop_interchange, + clang::options::OPT_fno_loop_interchange, + opts.OptimizationLevel == 3); if (args.getLastArg(clang::options::OPT_fexperimental_loop_fusion)) opts.FuseLoops = 1; diff --git a/flang/test/Driver/loop-interchange.f90 b/flang/test/Driver/loop-interchange.f90 index 1e5a11902709c..c9d88cd63cf5b 100644 --- a/flang/test/Driver/loop-interchange.f90 +++ b/flang/test/Driver/loop-interchange.f90 @@ -1,15 +1,15 @@ +! The driver only forwards an explicit -f[no-]loop-interchange; the -O3 +! default is applied in the frontend, so it is not visible in -###. ! RUN: %flang -### -S -floop-interchange %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE %s ! RUN: %flang -### -S -fno-loop-interchange %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s -! RUN: %flang -### -S -O0 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s -! RUN: %flang -### -S -O1 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s -! RUN: %flang -### -S -O2 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s ! RUN: %flang -### -S -O3 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s -! RUN: %flang -### -S -Os %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s -! RUN: %flang -### -S -Oz %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE %s ! CHECK-LOOP-INTERCHANGE: "-floop-interchange" ! CHECK-NO-LOOP-INTERCHANGE-NOT: "-floop-interchange" -! RUN: %flang_fc1 -emit-llvm -O2 -floop-interchange -mllvm -print-pipeline-passes -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE-PASS %s -! RUN: %flang_fc1 -emit-llvm -O2 -fno-loop-interchange -mllvm -print-pipeline-passes -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE-PASS %s +! +! Loop interchange is enabled by default only at -O3. +! RUN: %flang_fc1 -emit-llvm -O3 -mllvm -print-pipeline-passes -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE-PASS %s +! RUN: %flang_fc1 -emit-llvm -O2 -mllvm -print-pipeline-passes -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE-PASS %s +! RUN: %flang_fc1 -emit-llvm -O3 -fno-loop-interchange -mllvm -print-pipeline-passes -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-NO-LOOP-INTERCHANGE-PASS %s ! CHECK-LOOP-INTERCHANGE-PASS: loop-interchange ! CHECK-NO-LOOP-INTERCHANGE-PASS-NOT: loop-interchange >From 1b0a914d4e0c13920bff6ff67243ebadc28b1ec4 Mon Sep 17 00:00:00 2001 From: Madhur Amilkanthwar <[email protected]> Date: Mon, 17 Aug 2026 23:47:02 -0700 Subject: [PATCH 2/2] fixup! [Clang][Flang] Enable loop interchange by default at -O3 --- clang/lib/Frontend/CompilerInvocation.cpp | 1 - flang/lib/Frontend/CompilerInvocation.cpp | 1 - 2 files changed, 2 deletions(-) diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp index f023df260d55e..a92f2ba7092f5 100644 --- a/clang/lib/Frontend/CompilerInvocation.cpp +++ b/clang/lib/Frontend/CompilerInvocation.cpp @@ -1945,7 +1945,6 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, Opts.UnrollLoops = Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops, (Opts.OptimizationLevel > 1)); - // Loop interchange is only enabled by default at -O3. Opts.InterchangeLoops = Args.hasFlag(OPT_floop_interchange, OPT_fno_loop_interchange, (Opts.OptimizationLevel == 3)); diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp index d50dc4878e60d..58a4470e342a8 100644 --- a/flang/lib/Frontend/CompilerInvocation.cpp +++ b/flang/lib/Frontend/CompilerInvocation.cpp @@ -320,7 +320,6 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts, clang::options::OPT_fno_fp_sum_reassociation, false)) opts.SplitSumExpressionTree = 1; - // Loop interchange is only enabled by default at -O3. opts.InterchangeLoops = args.hasFlag(clang::options::OPT_floop_interchange, clang::options::OPT_fno_loop_interchange, opts.OptimizationLevel == 3); _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
