[llvm-branch-commits] [llvm] [2/2][AMDGPU] Insert IMPLICIT_DEF to provide a reaching def for unspilled reloads (PR #200126)

[Matt Arsenault via llvm-branch-commits]

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@@ -601,11 +601,79 @@ void AMDGPURewriteAGPRCopyMFMAImpl::eliminateSpillsOfReassignedVGPRs() const {
       return false;
     };
 
-    if (!llvm::all_of(Loads, IsLoadJointlyDominatedByStores)) {
-      LLVM_DEBUG(
-          dbgs() << "Skipping " << printReg(Slot, &TRI)
-                 << ": some reachable load not jointly dominated by stores\n");
-      continue;
+    // Collect basic blocks of any loads not jointly dominated by stores. After
+    // rewriting, we will attempt to insert a single IMPLICIT_DEF for those uses
+    // of NewVReg.
+    SmallVector<MachineBasicBlock *, 4> ProblematicLoadMBBs;
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arsenm wrote:

Problematic is wrong phrasing 

https://github.com/llvm/llvm-project/pull/200126