LiveIntervalAnalysis: Fix missing case in pruneSubRegValues()

pruneSubRegValues() needs to remove subregister ranges starting at
instructions that later get removed by eraseInstrs(). It missed to check
one case in which eraseInstrs() would remove an instruction.

Fixes http://llvm.org/PR32688

llvm-svn: 303396

2 files changed, 38 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/RegisterCoalescer.cpp b/llvm/lib/CodeGen/RegisterCoalescer.cpp
index 1803ea2b924..7b3a5d5c5ff 100644
--- a/llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ b/llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -2666,11 +2666,17 @@ void JoinVals::pruneSubRegValues(LiveInterval &LI, LaneBitmask &ShrinkMask) {
   // Look for values being erased.
   bool DidPrune = false;
   for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
-    if (Vals[i].Resolution != CR_Erase)
+    // We should trigger in all cases in which eraseInstrs() does something.
+    // match what eraseInstrs() is doing, print a message so
+    if (Vals[i].Resolution != CR_Erase &&
+        (Vals[i].Resolution != CR_Keep || !Vals[i].ErasableImplicitDef ||
+         !Vals[i].Pruned))
       continue;
 
     // Check subranges at the point where the copy will be removed.
     SlotIndex Def = LR.getValNumInfo(i)->def;
+    // Print message so mismatches with eraseInstrs() can be diagnosed.
+    DEBUG(dbgs() << "\t\tExpecting instruction removal at " << Def << '\n');
     for (LiveInterval::SubRange &S : LI.subranges()) {
       LiveQueryResult Q = S.Query(Def);
 
diff --git a/llvm/test/CodeGen/AMDGPU/regcoalesce-prune.mir b/llvm/test/CodeGen/AMDGPU/regcoalesce-prune.mir
new file mode 100644
index 00000000000..7d8c7bb105a
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/regcoalesce-prune.mir
@@ -0,0 +1,31 @@
+# RUN: llc -o - %s -mtriple=amdgcn-amd-amdhsa-opencl -run-pass=simple-register-coalescing | FileCheck %s
+---
+# Checks for a bug where subregister liveranges were not properly pruned for
+# an IMPLCITI_DEF that gets removed completely.
+#
+# CHECK-LABEL: name: func
+# IMPLICIT_DEF should be gone without llc hitting assertion failures.
+# CHECK-NOT: IMPLCITI_DEF
+name: func
+tracksRegLiveness: true
+body: |
+  bb.0:
+    undef %5.sub1 = V_MOV_B32_e32 0, implicit %exec
+    %6 = COPY %5
+    S_CBRANCH_VCCZ %bb.2, implicit undef %vcc
+
+  bb.1:
+    %1 : sreg_32_xm0 = S_MOV_B32 0
+    undef %0.sub0 : sreg_64 = COPY %1
+    %0.sub1 = COPY %1
+    %4 : vreg_64 = COPY killed %0
+    %5 : vreg_64 = IMPLICIT_DEF
+    %6 : vreg_64 = COPY killed %4
+
+  bb.2:
+    %2 : vgpr_32 = V_CVT_F32_I32_e32 killed %5.sub1, implicit %exec
+
+  bb.3:
+    %3 : vgpr_32 = V_CVT_F32_I32_e32 killed %6.sub1, implicit %exec
+    S_ENDPGM
+...