[RDA] isSafeToDefRegAt: Look at global uses

[samparker]

Summary

We weren't looking at global uses of a value, so we could happily overwrite the register incorrectly.

[SjoerdMeijer]

Looks like a good fix to me.

llvm/lib/CodeGen/ReachingDefAnalysis.cpp

 }
 
 bool ReachingDefAnalysis::isSafeToDefRegAt(MachineInstr *MI, int PhysReg,
                                            InstSet &Ignore) const {
   // Check for any uses of the register after MI.
   if (isRegUsedAfter(MI, PhysReg)) {
     if (auto *Def = getReachingLocalMIDef(MI, PhysReg)) {
       SmallPtrSet<MachineInstr*, 2> Uses;
-      getReachingLocalUses(Def, PhysReg, Uses);
+      getGlobalUses(Def, PhysReg, Uses);
       for (auto *Use : Uses)
         if (!Ignore.count(Use))
           return false;
     } else
       return false;
   }
 
   MachineBasicBlock *MBB = MI->getParent();

llvm/test/CodeGen/Thumb2/LowOverheadLoops/biquad-cascade-optsize-strd-lr.mir

body:             |
   ; CHECK:   $r7, $r5 = t2LDRDi8 $r0, 0, 14 /* CC::al */, $noreg :: (load 4 from %ir.i), (load 4 from %ir.i5)
   ; CHECK:   $r6, $r4 = t2LDRDi8 killed $r0, 8, 14 /* CC::al */, $noreg :: (load 4 from %ir.i7), (load 4 from %ir.i10)
   ; CHECK:   renamable $r0 = t2RSBri killed renamable $r6, 31, 14 /* CC::al */, $noreg, $noreg
   ; CHECK:   t2STMIA $sp, 14 /* CC::al */, $noreg, killed $r0, $r2, $r3 :: (store 4 into %stack.9), (store 4 into %stack.8), (store 4 into %stack.7)
   ; CHECK: bb.1.bb12 (align 4):
   ; CHECK:   successors: %bb.2(0x40000000), %bb.5(0x40000000)
   ; CHECK:   liveins: $r1, $r2, $r3, $r4, $r5, $r7
   ; CHECK:   $r9, $r8 = t2LDRDi8 $r7, 0, 14 /* CC::al */, $noreg :: (load 4 from %ir.i14), (load 4 from %ir.i20)
-  ; CHECK:   dead renamable $lr = nuw t2ADDri renamable $r5, 20, 14 /* CC::al */, $noreg, $noreg
+  ; CHECK:   renamable $lr = nuw t2ADDri renamable $r5, 20, 14 /* CC::al */, $noreg, $noreg
   ; CHECK:   $r6, $r12 = t2LDRDi8 $r7, 8, 14 /* CC::al */, $noreg :: (load 4 from %ir.i22), (load 4 from %ir.i24)
-  ; CHECK:   $lr = t2WLS renamable $r3, %bb.5
+  ; CHECK:   t2CMPri renamable $r3, 0, 14 /* CC::al */, $noreg, implicit-def $cpsr
+  ; CHECK:   tBcc %bb.5, 0 /* CC::eq */, killed $cpsr
+  ; CHECK:   tB %bb.2, 14 /* CC::al */, $noreg
   ; CHECK: bb.2.bb27:
   ; CHECK:   successors: %bb.3(0x80000000)
   ; CHECK:   liveins: $lr, $r1, $r2, $r3, $r4, $r5, $r6, $r7, $r8, $r9, $r12
   ; CHECK:   t2STRDi8 killed $lr, killed $r7, $sp, 12, 14 /* CC::al */, $noreg :: (store 4 into %stack.6), (store 4 into %stack.5)
   ; CHECK:   renamable $r0 = tLDRi renamable $r5, 0, 14 /* CC::al */, $noreg :: (load 4 from %ir.i13)
   ; CHECK:   renamable $r10 = t2LDRi12 renamable $r5, 16, 14 /* CC::al */, $noreg :: (load 4 from %ir.i28)
   ; CHECK:   tSTRspi killed renamable $r0, $sp, 9, 14 /* CC::al */, $noreg :: (store 4 into %stack.0)
   ; CHECK:   renamable $r0 = tLDRi renamable $r5, 1, 14 /* CC::al */, $noreg :: (load 4 from %ir.i34)
body:             |
   ; CHECK:   renamable $r4 = tLDRspi $sp, 8, 14 /* CC::al */, $noreg :: (load 4 from %stack.1)
   ; CHECK:   $r7 = tMOVr killed $r6, 14 /* CC::al */, $noreg
   ; CHECK:   $r5 = tMOVr $r9, 14 /* CC::al */, $noreg
   ; CHECK:   $lr = tMOVr $r0, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r6, renamable $r11 = t2SMULL killed $r9, killed renamable $r4, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r4 = tLDRspi $sp, 7, 14 /* CC::al */, $noreg :: (load 4 from %stack.2)
   ; CHECK:   renamable $r0, dead $cpsr = tSUBi8 killed renamable $r0, 1, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r9, renamable $r1 = t2LDR_POST killed renamable $r1, 4, 14 /* CC::al */, $noreg :: (load 4 from %ir.i38)
+  ; CHECK:   dead $lr = t2SUBri killed renamable $lr, 1, 14 /* CC::al */, $noreg, def $cpsr
   ; CHECK:   renamable $r6, renamable $r11 = t2SMLAL killed renamable $r8, killed renamable $r4, killed renamable $r6, killed renamable $r11, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r4 = tLDRspi $sp, 6, 14 /* CC::al */, $noreg :: (load 4 from %stack.3)
   ; CHECK:   $r8 = tMOVr $r5, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r6, renamable $r11 = t2SMLAL renamable $r7, killed renamable $r4, killed renamable $r6, killed renamable $r11, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r4 = tLDRspi $sp, 9, 14 /* CC::al */, $noreg :: (load 4 from %stack.0)
   ; CHECK:   renamable $r6, renamable $r11 = t2SMLAL killed renamable $r12, renamable $r10, killed renamable $r6, killed renamable $r11, 14 /* CC::al */, $noreg
   ; CHECK:   $r12 = tMOVr $r7, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r6, renamable $r11 = t2SMLAL renamable $r9, killed renamable $r4, killed renamable $r6, killed renamable $r11, 14 /* CC::al */, $noreg
   ; CHECK:   early-clobber renamable $r6, dead early-clobber renamable $r11 = MVE_ASRLr killed renamable $r6, killed renamable $r11, renamable $r3, 14 /* CC::al */, $noreg
   ; CHECK:   early-clobber renamable $r2 = t2STR_POST renamable $r6, killed renamable $r2, 4, 14 /* CC::al */, $noreg :: (store 4 into %ir.i39)
-  ; CHECK:   dead $lr = t2LEUpdate killed renamable $lr, %bb.3
+  ; CHECK:   tBcc %bb.3, 1 /* CC::ne */, killed $cpsr
+  ; CHECK:   tB %bb.4, 14 /* CC::al */, $noreg
   ; CHECK: bb.4.bb72:
   ; CHECK:   successors: %bb.5(0x80000000)
   ; CHECK:   liveins: $r5, $r6, $r7, $r9
   ; CHECK:   $r12 = tMOVr killed $r7, 14 /* CC::al */, $noreg
   ; CHECK:   $r7, $r4 = t2LDRDi8 $sp, 16, 14 /* CC::al */, $noreg :: (load 4 from %stack.5), (load 4 from %stack.4)
   ; CHECK:   $lr = t2ADDri $sp, 4, 14 /* CC::al */, $noreg, $noreg
   ; CHECK:   $r8 = tMOVr killed $r5, 14 /* CC::al */, $noreg
   ; CHECK:   t2LDMIA killed $lr, 14 /* CC::al */, $noreg, def $r2, def $r3, def $lr :: (load 4 from %stack.8), (load 4 from %stack.7), (load 4 from %stack.6)