Rework of the new interface for shrink wrapping
Based on comments from Hal
(http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150810/292978.html),
I've changed the interface to add a callback mechanism to the
TargetFrameLowering class to query whether the specific target
supports shrink wrapping. By default, shrink wrapping is disabled by
default. Each target can override the default behaviour using the
TargetFrameLowering::targetSupportsShrinkWrapping() method. Shrink
wrapping can still be explicitly enabled or disabled from the command
line, using the existing -enable-shrink-wrap=<true|false> option.
Phabricator: http://reviews.llvm.org/D12293
llvm-svn: 246463
diff --git a/llvm/lib/CodeGen/ShrinkWrap.cpp b/llvm/lib/CodeGen/ShrinkWrap.cpp
index 8af859f..7e2f151 100644
--- a/llvm/lib/CodeGen/ShrinkWrap.cpp
+++ b/llvm/lib/CodeGen/ShrinkWrap.cpp
@@ -78,6 +78,10 @@
STATISTIC(NumCandidatesDropped,
"Number of shrink-wrapping candidates dropped because of frequency");
+static cl::opt<cl::boolOrDefault>
+ EnableShrinkWrapOpt("enable-shrink-wrap", cl::Hidden,
+ cl::desc("enable the shrink-wrapping pass"));
+
namespace {
/// \brief Class to determine where the safe point to insert the
/// prologue and epilogue are.
@@ -148,6 +152,9 @@
/// shrink-wrapping.
bool ArePointsInteresting() const { return Save != Entry && Save && Restore; }
+ /// \brief Check if shrink wrapping is enabled for this target and function.
+ static bool isShrinkWrapEnabled(const MachineFunction &MF);
+
public:
static char ID;
@@ -319,8 +326,9 @@
}
bool ShrinkWrap::runOnMachineFunction(MachineFunction &MF) {
- if (MF.empty())
+ if (MF.empty() || !isShrinkWrapEnabled(MF))
return false;
+
DEBUG(dbgs() << "**** Analysing " << MF.getName() << '\n');
init(MF);
@@ -404,3 +412,20 @@
++NumCandidates;
return false;
}
+
+bool ShrinkWrap::isShrinkWrapEnabled(const MachineFunction &MF) {
+ const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
+
+ switch (EnableShrinkWrapOpt) {
+ case cl::BOU_UNSET:
+ return TFI->enableShrinkWrapping(MF);
+ // If EnableShrinkWrap is set, it takes precedence on whatever the
+ // target sets. The rational is that we assume we want to test
+ // something related to shrink-wrapping.
+ case cl::BOU_TRUE:
+ return true;
+ case cl::BOU_FALSE:
+ return false;
+ }
+ llvm_unreachable("Invalid shrink-wrapping state");
+}