[flang] enable loop-interchange at O3, O2, and Os

Author: sebpop

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -3149,3 +3149,16 @@ void tools::handleVectorizeSLPArgs(const ArgList &Args,
                    options::OPT_fno_slp_vectorize, EnableSLPVec))
     CmdArgs.push_back("-vectorize-slp");
 }
+
+void tools::handleInterchangeLoopsArgs(const ArgList &Args,
+                                       ArgStringList &CmdArgs) {
+  // FIXME: instead of relying on shouldEnableVectorizerAtOLevel, we may want to
+  // implement a separate function to infer loop interchange from opt level.
+  // For now, enable loop-interchange at the same opt levels as loop-vectorize.
+  bool EnableInterchange = shouldEnableVectorizerAtOLevel(Args, false);
+  OptSpecifier InterchangeAliasOption =
+      EnableInterchange ? options::OPT_O_Group : options::OPT_floop_interchange;
+  if (Args.hasFlag(options::OPT_floop_interchange, InterchangeAliasOption,
+                   options::OPT_fno_loop_interchange, EnableInterchange))
+    CmdArgs.push_back("-floop-interchange");
+}

clang/lib/Driver/ToolChains/CommonArgs.h

@@ -259,6 +259,10 @@ void renderCommonIntegerOverflowOptions(const llvm::opt::ArgList &Args,
 bool shouldEnableVectorizerAtOLevel(const llvm::opt::ArgList &Args,
                                     bool isSlpVec);
 
+/// Enable -floop-interchange based on the optimization level selected.
+void handleInterchangeLoopsArgs(const llvm::opt::ArgList &Args,
+                                llvm::opt::ArgStringList &CmdArgs);
+
 /// Enable -fvectorize based on the optimization level selected.
 void handleVectorizeLoopsArgs(const llvm::opt::ArgList &Args,
                               llvm::opt::ArgStringList &CmdArgs);

clang/lib/Driver/ToolChains/Flang.cpp

@@ -152,9 +152,7 @@ void Flang::addCodegenOptions(const ArgList &Args,
       !stackArrays->getOption().matches(options::OPT_fno_stack_arrays))
     CmdArgs.push_back("-fstack-arrays");
 
-  Args.AddLastArg(CmdArgs, options::OPT_floop_interchange,
-                  options::OPT_fno_loop_interchange);
-
+  handleInterchangeLoopsArgs(Args, CmdArgs);
   handleVectorizeLoopsArgs(Args, CmdArgs);
   handleVectorizeSLPArgs(Args, CmdArgs);
 

flang/docs/ReleaseNotes.md

@@ -33,6 +33,7 @@ page](https://llvm.org/releases/).
 ## New Compiler Flags
 
 * -floop-interchange is now recognized by flang.
+* -floop-interchange is enabled by default at -O2 and above.
 
 ## Windows Support
 

flang/test/Driver/loop-interchange.f90

@@ -1,7 +1,13 @@
 ! 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-LOOP-INTERCHANGE %s
+! RUN: %flang -### -S -O3 %s 2>&1 | FileCheck -check-prefix=CHECK-LOOP-INTERCHANGE %s
+! RUN: %flang -### -S -Os %s 2>&1 | FileCheck -check-prefix=CHECK-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: "-fno-loop-interchange"
+! CHECK-NO-LOOP-INTERCHANGE-NOT: "-floop-interchange"
 
 program test
 end program