Teach machine cse to commute instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121903 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 0143d0f..fc3f594 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -24,7 +24,6 @@
#include "llvm/ADT/ScopedHashTable.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@@ -33,6 +32,7 @@
STATISTIC(NumCSEs, "Number of common subexpression eliminated");
STATISTIC(NumPhysCSEs,
"Number of physreg referencing common subexpr eliminated");
+STATISTIC(NumCommutes, "Number of copies coalesced after commuting");
namespace {
class MachineCSE : public MachineFunctionPass {
@@ -368,7 +368,22 @@
FoundCSE = VNT.count(MI);
}
}
- // FIXME: commute commutable instructions?
+
+ // Commute commutable instructions.
+ bool Commuted = false;
+ if (!FoundCSE && MI->getDesc().isCommutable()) {
+ MachineInstr *NewMI = TII->commuteInstruction(MI);
+ if (NewMI) {
+ Commuted = true;
+ FoundCSE = VNT.count(NewMI);
+ if (NewMI != MI)
+ // New instruction. It doesn't need to be kept.
+ NewMI->eraseFromParent();
+ else if (!FoundCSE)
+ // MI was changed but it didn't help, commute it back!
+ (void)TII->commuteInstruction(MI);
+ }
+ }
// If the instruction defines physical registers and the values *may* be
// used, then it's not safe to replace it with a common subexpression.
@@ -430,6 +445,8 @@
++NumCSEs;
if (!PhysRefs.empty())
++NumPhysCSEs;
+ if (Commuted)
+ ++NumCommutes;
} else {
DEBUG(dbgs() << "*** Not profitable, avoid CSE!\n");
VNT.insert(MI, CurrVN++);
diff --git a/test/CodeGen/X86/machine-cse.ll b/test/CodeGen/X86/machine-cse.ll
index a8afdc8..e284776 100644
--- a/test/CodeGen/X86/machine-cse.ll
+++ b/test/CodeGen/X86/machine-cse.ll
@@ -37,3 +37,43 @@
declare void @bar(i32*)
declare fastcc i8* @foo(%struct.s2*) nounwind
+
+; rdar://8773371
+
+declare void @printf(...) nounwind
+
+define void @commute(i32 %test_case, i32 %scale) nounwind ssp {
+; CHECK: commute:
+entry:
+ switch i32 %test_case, label %sw.bb307 [
+ i32 1, label %sw.bb
+ i32 2, label %sw.bb
+ i32 3, label %sw.bb
+ ]
+
+sw.bb: ; preds = %entry, %entry, %entry
+ %mul = mul nsw i32 %test_case, 3
+ %mul20 = mul nsw i32 %mul, %scale
+ br i1 undef, label %if.end34, label %sw.bb307
+
+if.end34: ; preds = %sw.bb
+; CHECK: %if.end34
+; CHECK: imull
+; CHECK: leal
+; CHECK-NOT: imull
+ tail call void (...)* @printf(i32 %test_case, i32 %mul20) nounwind
+ %tmp = mul i32 %scale, %test_case
+ %tmp752 = mul i32 %tmp, 3
+ %tmp753 = zext i32 %tmp752 to i64
+ br label %bb.nph743.us
+
+for.body53.us: ; preds = %bb.nph743.us, %for.body53.us
+ %exitcond = icmp eq i64 undef, %tmp753
+ br i1 %exitcond, label %bb.nph743.us, label %for.body53.us
+
+bb.nph743.us: ; preds = %for.body53.us, %if.end34
+ br label %for.body53.us
+
+sw.bb307: ; preds = %sw.bb, %entry
+ ret void
+}