[ARM][LowOverheadLoops] Check scalar predicates

When trying to remove the loop iteration count, check that the
instruction will always execute.

Differential Revision: https://reviews.llvm.org/D73682

diff --git a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
index 1211c0a..e973202 100644 (file)
--- a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
+++ b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
@@ -835,6 +835,9 @@ MachineInstr* ARMLowOverheadLoops::ExpandLoopStart(LowOverheadLoop &LoLoop) {
       while (!Chain.empty()) {
         MachineInstr *MI = Chain.back();
         Chain.pop_back();
+        if (TII->getPredicate(*MI) != ARMCC::AL)
+          continue;
+
         if (RDA->isSafeToRemove(MI, Remove, Ignore)) {
           for (auto &MO : MI->operands()) {
             if (!MO.isReg() || !MO.isUse() || MO.getReg() == 0)

diff --git a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
index 5998023..70c20dd 100644 (file)
--- a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
+++ b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
@@ -1,5 +1,5 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
-# RUN: llc -mtriple=thumbv8.1m.main -mattr=+mve -run-pass=arm-low-overhead-loops %s -o - | FileCheck %s
+# RUN: llc -mtriple=thumbv8.1m.main -mattr=+mve -run-pass=arm-low-overhead-loops %s -o - --verify-machineinstrs | FileCheck %s
 
 --- |
   define hidden arm_aapcs_vfpcc void @dont_ignore_vctp(float* %pSrc, float* %pDst, i32 %blockSize) local_unnamed_addr #0 {
@@ -100,8 +100,11 @@ body:             |
   ; CHECK:   frame-setup CFI_INSTRUCTION def_cfa_offset 8
   ; CHECK:   frame-setup CFI_INSTRUCTION offset $lr, -4
   ; CHECK:   frame-setup CFI_INSTRUCTION offset $r7, -8
-  ; CHECK:   renamable $r3, dead $cpsr = tLSLri killed renamable $r2, 1, 14, $noreg
-  ; CHECK:   t2IT 11, 8, implicit-def dead $itstate
+  ; CHECK:   renamable $r3, dead $cpsr = tLSLri renamable $r2, 1, 14, $noreg
+  ; CHECK:   renamable $r12 = t2MOVi 4, 14, $noreg, $noreg
+  ; CHECK:   tCMPi8 renamable $r3, 4, 14, $noreg, implicit-def $cpsr
+  ; CHECK:   t2IT 11, 8, implicit-def $itstate
+  ; CHECK:   dead $r12 = t2LSLri killed renamable $r2, 1, 11, killed $cpsr, $noreg, implicit killed renamable $r12, implicit killed $itstate
   ; CHECK:   renamable $r2 = tLEApcrel %const.0, 14, $noreg
   ; CHECK:   renamable $q0 = MVE_VLDRWU32 killed renamable $r2, 0, 0, $noreg :: (load 16 from constant-pool)
   ; CHECK:   $lr = MVE_DLSTP_32 killed renamable $r3