[m88k] Enable further matching of immediates

The matcher generated from the SDAG patterns does not honor the
isCommutable flag. An easy solution is to swap the operands if the
instruction is commutable and the first operand is constant.

2 files changed, 37 insertions, 0 deletions

diff --git a/llvm/lib/Target/M88k/GISel/M88kPostLegalizerLowering.cpp b/llvm/lib/Target/M88k/GISel/M88kPostLegalizerLowering.cpp
index 49b7c84..aa29756 100644
--- a/llvm/lib/Target/M88k/GISel/M88kPostLegalizerLowering.cpp
+++ b/llvm/lib/Target/M88k/GISel/M88kPostLegalizerLowering.cpp
@@ -394,6 +394,23 @@ bool M88kPostLegalizerLoweringInfo::combine(GISelChangeObserver &Observer,
                                             MachineIRBuilder &B) const {
   M88kGenPostLegalizerLoweringHelper Generated(GeneratedRuleCfg);
 
+  // If the instruction is commutable and the first operand is a constant, then
+  // swap the operands. The matcher generated from the SDAG patterns expects the
+  // constant always as the second operand, otherwise operand is not matched as
+  // immediate.
+  if (MI.isCommutable()) {
+    assert(MI.getNumExplicitOperands() == 3 && "Not a binary operation");
+    unsigned SrcOpc =
+        getDefIgnoringCopies(MI.getOperand(1).getReg(), *B.getMRI())
+            ->getOpcode();
+    if (SrcOpc == TargetOpcode::G_CONSTANT ||
+        SrcOpc == TargetOpcode::G_FCONSTANT) {
+      Observer.changingInstr(MI);
+      B.getTII().commuteInstruction(MI, false, 1, 2);
+      Observer.changedInstr(MI);
+    }
+  }
+
   if (Generated.tryCombineAll(Observer, MI, B, KB, ReplaceSignedDiv,
                               AddZeroDivCheck))
     return true;
diff --git a/llvm/test/CodeGen/M88k/add.ll b/llvm/test/CodeGen/M88k/add.ll
new file mode 100644
index 0000000..3e15d9e
--- /dev/null
+++ b/llvm/test/CodeGen/M88k/add.ll
@@ -0,0 +1,20 @@
+; Test addition/subtraction.
+;
+; RUN: llc < %s -mtriple=m88k-openbsd -mcpu=mc88100 -verify-machineinstrs -m88k-enable-delay-slot-filler=false | FileCheck %s
+; RUN: llc < %s -mtriple=m88k-openbsd -mcpu=mc88110 -verify-machineinstrs -m88k-enable-delay-slot-filler=false | FileCheck %s
+
+define i32 @f1(i32 %a) {
+; CHECK-LABEL: f1:
+; CHECK:       addu %r2, %r2, 512
+; CHECK-NEXT:  jmp %r1
+  %sum = add i32 %a, 512
+  ret i32 %sum
+}
+
+define i32 @f2(i32 %a) {
+; CHECK-LABEL: f2:
+; CHECK:       addu %r2, %r2, 512
+; CHECK-NEXT:  jmp %r1
+  %sum = add i32 512, %a
+  ret i32 %sum
+}