[flang] Propagate lowering options from driver.

This commit addresses concerns raised in D129497.

Propagate lowering options from driver to expressions lowering
via AbstractConverter instance. A single use case so far is
using optimized TRANSPOSE lowering with O1/O2/O3.

bbc does not support optimization level switches, so it uses
default LoweringOptions (e.g. optimized TRANSPOSE lowering
is enabled by default, but an engineering -opt-transpose=false
option can still override this).

Differential Revision: https://reviews.llvm.org/D130204

3 files changed, 12 insertions, 1 deletions

diff --git a/flang/lib/Frontend/CompilerInstance.cpp b/flang/lib/Frontend/CompilerInstance.cpp
index 418c83c..5a33f5b 100644
--- a/flang/lib/Frontend/CompilerInstance.cpp
+++ b/flang/lib/Frontend/CompilerInstance.cpp
@@ -151,6 +151,8 @@ bool CompilerInstance::executeAction(FrontendAction &act) {
   allSources->set_encoding(invoc.getFortranOpts().encoding);
   // Create the semantics context and set semantic options.
   invoc.setSemanticsOpts(*this->allCookedSources);
+  // Set options controlling lowering to FIR.
+  invoc.setLoweringOptions();
 
   // Run the frontend action `act` for every input file.
   for (const FrontendInputFile &fif : getFrontendOpts().inputs) {
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index f794eb7..a75c04d 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -794,3 +794,12 @@ void CompilerInvocation::setSemanticsOpts(
       .set_warningsAreErrors(getWarnAsErr())
       .set_moduleFileSuffix(getModuleFileSuffix());
 }
+
+/// Set \p loweringOptions controlling lowering behavior based
+/// on the \p optimizationLevel.
+void CompilerInvocation::setLoweringOptions() {
+  const auto &codegenOpts = getCodeGenOpts();
+
+  // Lower TRANSPOSE as a runtime call under -O0.
+  loweringOpts.setOptimizeTranspose(codegenOpts.OptimizationLevel > 0);
+}
diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
index 7591e1a..4ebe2ea 100644
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -148,7 +148,7 @@ bool CodeGenAction::beginSourceFileAction() {
       *mlirCtx, defKinds, ci.getInvocation().getSemanticsContext().intrinsics(),
       ci.getInvocation().getSemanticsContext().targetCharacteristics(),
       ci.getParsing().allCooked(), ci.getInvocation().getTargetOpts().triple,
-      kindMap);
+      kindMap, ci.getInvocation().getLoweringOpts());
 
   // Create a parse tree and lower it to FIR
   Fortran::parser::Program &parseTree{*ci.getParsing().parseTree()};