[PATCH] D77208: [PowerPC] Remove unnecessary XSRSP instruction in MI peephole

[Qiu Chaofan via Phabricator via llvm-commits]

qiucf created this revision.
Herald added subscribers: llvm-commits, shchenz, kbarton, hiraditya, nemanjai.
Herald added a project: LLVM.
qiucf added a child revision: D64193: [PowerPC] Add exception constraint to FP rounding operations.
Herald added a subscriber: wuzish.
qiucf added reviewers: nemanjai, jsji, PowerPC.

This is found when looking at test results in D64193 <https://reviews.llvm.org/D64193>. Eliminate `xsrsp` instruction besides `frsp`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77208

Files:
  llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
  llvm/test/CodeGen/PowerPC/mi-simplify-code.mir


Index: llvm/test/CodeGen/PowerPC/mi-simplify-code.mir
===================================================================
--- llvm/test/CodeGen/PowerPC/mi-simplify-code.mir
+++ llvm/test/CodeGen/PowerPC/mi-simplify-code.mir
@@ -56,7 +56,7 @@
 # CHECK-LABEL: remove_xsrsp
 # CHECK: sldi 4, 4, 2
 # CHECK-NEXT: lfsux 0, 3, 4
-# CHECK-NEXT: xsrsp 0, 0
+# CHECK-NOT: xsrsp
 # CHECK-NEXT: lfs 1, 8(3)
 # CHECK-NEXT: xxmrghd	0, 1, 0
 # CHECK-NEXT: xvcvdpsp 34, 0
Index: llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
+++ llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
@@ -544,7 +544,8 @@
           // Remove the passed FRSP instruction if it only feeds this MI and
           // set any uses of that FRSP (in this MI) to the source of the FRSP.
           auto removeFRSPIfPossible = [&](MachineInstr *RoundInstr) {
-            if (RoundInstr->getOpcode() == PPC::FRSP &&
+            unsigned Opc = RoundInstr->getOpcode();
+            if ((Opc == PPC::FRSP || Opc == PPC::XSRSP) &&
                 MRI->hasOneNonDBGUse(RoundInstr->getOperand(0).getReg())) {
               Simplified = true;
               Register ConvReg1 = RoundInstr->getOperand(1).getReg();


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